pressure measurement in shale

PRESSURE MEASUREMENT IN SHALE

Shale Pressure Measurements Methods

A project by:Naser Soufi

2009

PRESSURE MEASUREMENT IN SHALE-----------------------------------------------------------------------------------------------------------------

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ForewordThe present project was initiated in connection with my work on specialization course“TPG 4520 Drilling Technology”.I would like to express my thanks to my supervisor Professor Pål Skale and PHDstudent Aminul Islam as they helped me for more sources in this rapport! Finally Iwould like to thank all my fellow students at the Department of PetroleumEngineering and Applied Geophysics. Mutual encouragement and professional aswell as social discussion has truly enriched my time as a student.


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Abstract:

Formation pore pressure can be determined with information from several sources.All sources should be utilized during planning, executing and analyzing drilling effort.Reservoir engineers, geologists and geophysicists can make important contributionsparticularly in regard to stratigraphic correlations. “Shale is a fine grained, clasticmineral, especially quartz and calcite. 1 Shale is the predominant lithology found inpetroleum basins. Most of drilling and seismic travel times take place in shale.Mechanically shale remains the least understood rock type because lack of reliablepressure measurements. Pore pressure, together with total stress, defines the“effective stress” which controls the mechanical behavior of rocks in terms of strengthand stiffness. Shale is exceedingly variable in all of their properties. This variabilityfurther complicates the definition of shale normal compaction curves as shalecompaction characteristics vary considerably.Shale is a tight material with a sufficient low permeability. Porosity in shale variesbetween 50 to 5 % when depth increasing. It’s extremely difficult to estimate andmeasured the porosity in shale. That’s a challenge for estimation of variation of porepressure in shale. In over pressured shale’s which contain pressured water, densityis lower and porosity is higher then normal. There are several method have beenexisted to estimate pore pressure in shale since 1950. Many authors have outlineprocedures for estimating formation (shale) pressure using data obtained fromelectrical and acoustical surveys.

This project has three parts including six chapters for describe and solve theproblem. Part one is based on challenge on porosity estimation in shale and how tosolve the problem and measurements methods.Part two is based on direct pressure measurements methods, and part three istheoretical indirect methods for measuring pressure based on well data analyzing todistribute the realistic solution with real well data, curve analyzing based on electricalor logical surveys equipment. Thus, we review the most useable methods of shalepressure estimation and fit the real well data to these methods and Simulated andanalyses them as it has been shown in Appendixes.


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Content: Page

Foreword……………………………………………………………….………………….3

Abstract………………………………………………………………………………...….4

Introduction........................................................................ .....................................9

Part I: Challenge of Porosity…………………………………………………….11

Chapter 1: Challenge of Porosity Measurement in Shale …...………12

1. Bases for porosity-based techniques………………………….…………….14 1.1The effective stress concept……………………………………….…..14 1.1.2 Normal Trend………………………………………………………..16

1.2 Determination of shale porosity ……………………………………....17 1.2.1 Porosity determination of shale by using Resistivity ……………17 1.2.2 The Mechanical Module…………………………………………….20

1.3 Estimation of porosity from Wireline logs…………….……………….22 1.3.1 Estimation of porosity from sonic logs…………………………….22 1.3.2 Estimation of porosity from density log……………………………23 1.3.3 Estimation of porosity from Resistivity log using Archie Eq….....25

1.4 Summary and conclusion………………………………………………26

Part II:

Direct pressure measurement……………………………………………………………...27

Chapter 2: Direct pressure measurement in formation…………………………….28

2. Direct measurement of permeable pore pressure……….……...……..30

2.1 RFT a briefly review………………………………………….………...30 2.1.1 The RFT Tool…………………………………………..…………...30 2.1.2 Principle of RFT works……………………………..………………30 2.1.3 Application of RFT……………………………..…………………...31 2.1.4 Limitation of RFT…………………………..……………………….32

2.2 Drill Stem Test(DST)…………………………………………...………32 2.2.1 Limitation of the DST……………….……………………………...32

2.3 RFT and estimation of pressure in shale……………….…………....33 2.4 Summary of the pressure determination……………………………..34


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Chapter 3: Direct pressure measurement in Shale………………………………..…35

3.1 Application………………………………………………………………37 3.2 Existing Techniques…………..……………………………………....37

3.2.1 Pore pressure measurement in petroleum industry…...…37 3.3.2 Limitations of this method…………………………………..38

3.3 Basic Principle……………………………………...………………….38 3.3.1Chemical and Temperature effect………………………………..38 3.3.2 Pore pressure excess from wellbore fluid during drilling….…..39 3.3.3 Cement sealing……………………………………………………39

3.4 Measurement methods…………………….…………………..…......40 3.4.1 Short Term Measurement………………………………………...41 3.4.2 Long Term Measurement………………………………………...42

3.5 Challenges…………………………………………………..…………43

Part III:

Indirect Pressure Measurement…………………………………………..….…..44

Chapter 4: seismic While Drilling (SWD)……………………………………………….45

4.1 Seismic While Drilling Operation and Application……………..…...47 4.1.1 Planning phase………………………………………………..…...48 4.1.2 System design and Consideration………………………...…..…48 4.1.3 SWD Tool…………………………….…………………….……....50 4.1.4: Process of SWD………………………………………… ….......50 4.1.5 SWD Application………………………………………….......……50

4.2 Drill-Bit Seismic…………………………………………………. ……53 4.2.1 Application……………………………………………………. …..53 4.2.2 Procedure technique………………………………………....…….53 4.2.3 Advantage drill-bit seismic…………………………………… …...55 4.2.4 Limitation drill-bit seismic…………………………………….. …..55

4.3 Vertical Seismic Profiling (VSP)…………………..……… ……..…56

4.3.1 Advantage of VSP-MD…………………………………… …….….56 4.3.2 Limitation of VSP- MD…………………………………… ………...57

4.4 SWD using Swept Impulse Source……………………… …….…..58

4.4.1 Seismic profiling using Swept Impulse Tool (SIT)…….. ……..…59 4.4.2 Advantage of Swept Impulse Tool …………………….. …….….59 4.4.3 Limitations……………………………………………..…… …..….59


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Chapter 5: MWD/LWD………………………………………………………………..… 60

5.1 Measurement while drilling (MWD)…………………………….. ……62

5.1.1 Types of transmitted information…………………………..… ….62 5.1.2 Directional information………………………………………..… ..62 5.1.3 Drilling mechanics information………………………….…….… 63

5.1.4 Formation properties………………………………………….…. 63 5.2 Data transmission methods………….……………………….….. 63

5.2.1 Mud pulse telemetry………………………………………….. 63 5.2.2 Positive Pulse ………………………………………………… 64 5.2.3 Negative Pulse …………………………………...…………... 64 5.2.4 Continuous Wave …………………………………………….. 65

5.3 Electromagnetic telemetry (EM Tool)……………………….….. 66 5.4 Wired Drill Pipe…………………………………………………… 66 5.5 Retrievable tools………………………………………………….. 67 5.6 Logging while drilling (LWD) …………………………….…… 68

5.6.1 Available LWD Measurements……………………………… 68 5.7 MWD/LWD Advantages…………………………………………. 70 5.8 MWD/LWD Disadvantages……………………………………… 70

Chapter 6: Miscellanies…………………………………………………………… 72

6.1 Eaton Method……………………………………………………… 74 6.2 Equivalent Method………………………………………………… 75 6.2.1 Calculation of Overburden Gradient………………………… 77

6.3 The Ratio Method ………………………………………………… 78 6.3.1 Isodensity Concept…………………………………………… 79 6.3.2 Establishing isodensity line………………………………….. 79

6.4 Vertical and Horizontal Models Method………………………… 81 6.5 Pore Pressure in Over consolidated Shale…………………….. 83 6.6 Compaction Concept Method……………………………………. 85 6.7 Power Law Relationship Method………………………………... 87

References:........................................................................... ......................... 91

Appendix A:……………………………………………………………………………… 93Predication of Pore pressure using Eaton Method

Appendix B:……………………………………………………………………………… 112Predication of Pore pressure using equivalent depth method.Appendix C:…………………………………………………………………………… 117Predication of Pore pressure using Vertical & Horizontal Methods


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Appendix D:…………………………………………………………………………… 129Predication of Pore pressure using overconsolidated Pore pressure method

Appendix E:…………………………………………………………………………… 138Nomenclature


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List of Figures: page

Ref.

Fig.1.1 [- ] Illustration of Overburden Pore fluid rock grain in deep sediment rocks…15Fig.1.2 [- ] Illustration of main stress and direction of force on a sample rock in a

deep sediment rocks…………………………………………………………...15Fig.1.3 [3] Pressure-Depth shows the relationship between total stress, pore pressure

and effective stress……………………………………………..……………...16Fig.1.4 [3] Bases for porosity based on pore pressure predication ............................16Fig.1.5 [- ] Illustration of Normal Trend Line……………………………………………...17Fig.1.6 [4] Cation distribution in Clay particles…………………………………………...18Fig.1.7 [8] Shale resistivity…………………………………………………………………..19Fig.1.8 [- ] Porosity vs. depth based on Wyllie and Raiga Clemenceaue Methods…....24Fig.1.9 [- ] Illustration in variation in estimate of the porosity from a density log using

grain densities…………………………………………………………………….25Fig.2.1 [9] Modern Multi Tester Tool (RFT, DST,…) from schlumberger ……….….....31Fig.2.2 [8] Typical analog pressure record in low permeability formation……………...31Fig.2.3 [9] RFT and sampling principle……………………………………………………..32Fig.2.4 [7] Estimation of pore pressure in shale based on extra plotting on RFT data in

Nile Delta Egypt…………………………………………………………………..34Fig.3.1 [10] Option for pore pressure Measurement in Shale…………….….…………..41Fig.3.2 [10] Schematic pore pressure measurement system…….………………..……..42Fig.3.3 [11] Image of Halliburton Geo Tap……………………………………...…………..42Fig.4.1 [12] Rig set up and system design for SWD including boat operations………...50Fig.4.2 [12] Sensors on the SWD Tool……………………………………..…….………....51Fig.4.3 [ - ] Schematic of SWD process………………………..…………………………....52Fig.4.4 [12] SWD Process…………………………………………………………………….53Fig.4.5 [14] Illustration of acoustic Radiation Pattern of the Tri-Cone Bit………………..54Fig.4.6 [14] Cross correlating the accelerometer signal…………………………………...55Fig.4.7 [14] Transfer of the wireline seismic technology to drilling operation……………57Fig.4.8 [14] Operation procedures of VSP-WD surveys…………………...………………58Fig.4.9 [17] Comparing of VSP&VSP look-ahead done by DNO…………………………58Fig.5.1 [20] Positive Mud pulse System……………………………………………………..65Fig.5.2 [20] Negative Mud pulse System…………………………………..………………..65Fig.5.3 [23] Position of Mud Pulse Telemetry in Drill String………………………...…….65Fig.5.4 [20] Continuous wave (Mud Siren) System….……………………………...……..65Fig.5.5 [- ] Principle of EM-effects in MWD/LWD………….………………………………67Fig.5.6 [23] Image of Wired Drill Pipe………..……...………..……………………………..67Fig.5.7 [23] Section view of double-shouldered pin tool joint,……………………..…….68Fig.5.8 [-] Principle of the LWD…………………….…………………………………………69Fig.6.1 [22] Pore pressure predication based on Eaton method…………………….……75Fig.6.2 [ - ] Principle of the Equivalent depth method……………………………………..76Fig.6.3 [22] Ratio Method: Principle of the dc-exponent…………………………..………79Fig.6.4 [22] Example of a set of isodensity lines……………………………………………80Fig.6.5 [22] Shows how to setting isodensity lines in Ratio Method………………...……80


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Fig.6.6 [ - ] Principle of Vertical-Horizontal Methods in deep water depth….……………82Fig.6.7 [24] Shows the comparing of the Vertical vs. Horizontal pressure measurements

methods on shale………………………………………………………………...83Fig.6.8 [ - ] Determination of pore pressure in over consolidated Shale…..……………..86Fig.A1: [ - ] Variation of Sonic travel Time vs. Depth………………………….…………….99Fig.A2: [ - ] Pore pressure predication using Eaton sonic log method………….………100Fig.A3: [ - ] Variation of traveltime sonic log vs.depth……………………………………..109Fig.A4: [ - ] Pore pressure predication using Eaton sonic travel time method…...……..110Fig.A5: [ - ] Variation of Resistivity Vs. depth………………………………………………111Fig.A6: [ - ] Pore pressure predication using Eaton Resistivity method…………………112

Fig.B1: [ - ] variation of porosity vs. depth in Norne felt well nr: N6608 10-E-3 H…...…117Fig.B2: [ - ] Predication of pore pressure using equivalent depth method……………….117

Fig.C1: [ - ] Principle of predication pore pressure in Horizontal & Vertical Methods…..118Fig.C2: [ - ] Velocity vs. depth…………………………………………………………………126Fig.C3: [ - ] Pore pressure predication using vertical method……………………………..127Fig.C4: [ - ] Pore pressure predication using Horizontal method(X=3)…………………...128Fig.C4: [ - ] Pore pressure predication using Horizontal method(X=2)……..…………….129Fig.D1: [ - ] sonic travel time vs. depth……………………………………………………….133Fig.D2: [ - ] Velocity and Normal compaction Curve………………………………………..134Fig.D3: [ - ] Pore pressure predication using Eaton Method………………………………136Fig.D4: [ - ] Pore pressure predication using Bower’s method…………………………....137Fig.D5: [ - ] Pore pressure predication using overcosolidated model…………………....138


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Introduction:

An important parameter for well planning is the knowledge about the formation porepressure. Shale is one of the most important rocks which can be found in all reservoirrocks, often with an abnormally high pore pressure. And also detecting of abnormallyhigh pore pressure is an important task in every drilling program. Overpressuresediments are generally caused by sequence of events where becomes trapped byfault or non- permeable barriers in sediments at depth. In a normally pressuredformation the water was forced out by normal increases in overburden pressure. Butabnormally pressure is caused by releases of water into the sedimentary poresystem, Clay diagenesis, normal compaction and other mechanisms are stronglyrelated. In over pressured shale which contains pressured water, density is lower andporosity is higher then normal.Shale comprises a large proportion of most sedimentary basins and forms the sealand source rocks for many hydrocarbon reservoirs .Shale is a tight material with asufficient low permeability. Because of their low permeability, there is great interestin using shale as host rocks for waste storage. Porosity in shale varies between 50 to5 % when depth increasing. It’s extremely difficult to estimate and measured theporosity in shale. That’s a challenge for direct measurement of variation of porepressure in shale. several method exist to estimate pore pressure in shale since1950.Many authors have outline procedures for estimating formation (shale) pressureusing data obtained from electrical and acoustical surveys. Some others as Eaton,Hubbert, Willis and Mathews have outline procedures for estimating fracture porepressure. Knowledge of these two parameters (formation & fracture pressure) isimportant in planning and drilling future wells.In fact one can divided these methods in two categories. Direct pressuremeasurement and indirect measuring methods. Direct pressure measurement inporous and permeable formation (RFT) has been made for decades. But directmeasurement of pore fluid pressure by the modular dynamic test or repeat formationtest tools in shale seems to be impossible due to their low permeability. The use ofshale compaction curves is thus the basis of several methods of pore fluid pressureestimation, pressure from seismic, wire line and in basin modeling. All these methodsrequire the definition of a normal compaction curve (NCC), or set of normalcompaction curves for the shale. These curves are typically empirical, being basedon regional experience or using calibration from soil mechanics experiments, butsome is based on work in the rock mechanics. The most of these methods based ondetection of normal pressure trend comparing with an abnormal trend in formation(especially Shale) to obtain overburden gradient pressure in the pointed depth. Othermethods as Seismic While Drilling (SWD), Logging While Drilling (LWD) and verticalSeismic Profiling (VSP) are the new technology for more accuracy of data and welllogging for estimation of pore pressure in shale which is used by the most of oilcompanies. All these used on in indirect pressure measurement. The direct pressuremeasurement in shale (“MESPOSH”) has been obtained since 2000(?) by some oilcompanies as Statoil, BP and others! This method considers for two mainapplications as Long term and short term pressure measurement. Effects of localstress, chemical and temperature on pressure measurement have been obtained.These methods shows the more can be learned about shale, directly bymeasurement or indirectly by inference, the better our position will be in interpretingand understanding the causes of the instability of pressure variations. Thisknowledge can lead us to more realistic application of technology and product


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development to the problem of controlling of unstable shale. In the petroleumindustry, shale causes billions of dollars in losses annually through, for example,pore-pressure-related kicks, blow-outs, and wellbore instability. Shale has a decisiveimpact on fluid-flow and seismic-wave propagation because of their low permeabilityand anisotropic microstructure. Thus we review the most of useable pressureestimation and try to present the new methods and fit the real well data to thesemethods. Simulate and analyses them.

.


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Part I:

Challenge of porosity in Shale


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Chapter 1:

Challenge of Porosity Measurement in Shale


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Introduction

Fluid pressure estimation down well and its accuracy is one of important fact for safeand economical drilling. Standard direct methods of pore pressure determination inshale are impossible because of shale’s low permeability. wireline loges commonlyused for estimation of pore pressure in offset wells .A method combining electricaland mechanical models to estimate pore fluid pressures from wireline logs has beendeveloped since 1950s.this methods reduce uncertainty involved in estimatingporosity from the logs and includes a simple model of mud rock lithology in thecalculation of fluid pressure. Porosity is commonly used to estimate pore pressure. Ifassume all shale behaved in a homogeneous manner in response to increasingeffective stress, this estimation process would be relatively simple. The commoninference of overpressure from porosity data from wireline on the assumption thatoverpressured shale is under compacted relative to its depth of burial is flawed.As we know the shale compaction is strongly dependent on lithology. Thus acombination of detailed rock data and suitable soil mechanics will lead us to anincreased ability for estimating pore pressure. Porosity estimation is one of thischallenges which knowledge about the quantity of it, leads us to put a big step topore pressure estimation. In this chapter we try to a benefit description of porosityestimation methods.


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1. Bases for porosity-based techniques

1.1 The effective stress concept

Terzaghi stress relationship is basis for porepressure predication and pore pressure in thesimplest form is:

pvobtot,Z P …………………….1.1Where:

obtot,Z : Total stress or Overburden

v : Effective stress

pP : Pores pressure

And porosity can be calculated from:)Kexp( vi ……………………...1.2

: Porosity of shale @ depth Di : Initial shale porosity @ surface

K : constantv : Effective stress

The total vertical stress ( v ) is derived fromoverburden which is combined weight of thesediments and contained fluids. The density log ordensity-sonic transform is used, coupled with anestimate of average sediment density from the topof the logged interval to seabed. Incorrect ofaverage density estimation leads to a systematicerror in pore pressure predication in the formation.

The magnitude of the two horizontal stress ( Hh , )is less well constrained; h can be most readilyestimated from borehole data, while the magnitudeof H is only rarely known. In practice most ofengineers use vertical effective stress( )pvv P , (also known as overburden orlithostatic pressure Fig.1.3) as a proxy for meaneffective stress. hence that, there is a tendency touse vertical effective stress in pore pressure predication.


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If the pore pressure is unknown in theabove equation, where dose themagnitude of the effective stress comfrom? Effective stress (grain to graincontact stress) is the principal drivingmechanism for compaction ofcompressible sediments. Themagnitude of the effective stressincrease with depth when the porepressure remains hydrostatic ornormal which in turn reduction ofporosity (Fig.1.4).porosity can beused, under the right conditions, as adirect indicator of effective stress. Withoverpressure due to effectivedewatering, compaction is slower thanexpected relative to the depth of burialand normal effective stress. Althoughthe sediments are overpressueredthey still retain the correct relationshipbetween porosity and effective stress(Fig.1.3).

In this case the rocks are undercompaction and they will holdsediments properties, such as porosityand permeability, which are associatedwith shallower depths of burial. Thisframework describe the basis forporosity-based pore pressurepredication, in which porosity assumedto be controlled slowly by compaction(i.e. no chemical involved) and toreflect the current effective stress ofsediment. Theses principles aresummarized on (Fig 1.4).

Practically during conventional oilfielddrilling operations, porosity is notmeasured directly. Rather porosityvalues can be obtained from wirelineresponse (e.g. density, sonic,resistivity, neutron log), or a porosityattribute may be used directly, forexample velocity data derived fromseismic. These methods have goodresults in low temperature, young, fine-


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grained sediments, particularly where the lithology remains similar (in compositionand grain size) throughout the section drilled, and where an upper shallow sectionexhibits a recognizable” normal compaction curve”. However porosity based porepressure predication dos not always deliver satisfactory pore pressure estimation,either because these assumption are not valid, or because there is insufficient data.There are several reasons for failure of the traditional porosity-based methods,especially in older (higher Temperature) basins as shale and where mixed lithologiesare found.

These solutions are found in: Calibration using offset wells-essentially introducing a “fudge factor” which will

be locally developed. Maximizing the number of direct pressure measurements Employing multiple complementary techniques to help understanding the

uncertainty.

There are several methods employed to obtain porosity in shale based on porepressure predication (e.g. Eaton Ratio Method an Equivalent Depth Method,etc…)all of these methods are best suited to pore pressure resulting fromdisequilibrium compaction, and require development of a type curve tocharacterize the change of porosity with depth, referred to as the “normalcompaction curve”. ]1[

1.1.2 Normal Trend

It is widely known that differentlithology compact at different rates,and from contrasting startingporosity. Lithological variability isaccounted for by” best fit” of theshallow data, assumed to benormally compacted if the porosity isdecreasing with increasing depth.This normal compaction curve isused to compare actual porosity onthe curve such that an estimation ofeffective stress can be made for porepressure estimation. Alternative tobest fit of data include:

A standard algorithm todescribe normal compactionbehavior of the samelithology, for example theshale compaction curve ofBalawin and Butler (1985)

A used-defined porosity depthcurve or similar functionbased on local experience.


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Once the normal compaction curve is defined, the pore pressure predication involvescomparison between observed porosity (and rather the attribute which is reflectingchanging porosity, such as interval velocity or wireline density) and the normalcompaction curve. The comparison is made at the depth of interest when usingcurrent methods (e.g. Eaton Method and etc...) or comparison of the same porosityvalue on the normal compaction curve using Equivalent Depth Method .both methodassume that the compaction is mechanical, and both can provide pore pressureestimation when the origin of overpressure is under compaction and the sedimentsare young and low temperature. 1

1.2 Determination of shale porosity

1.2.1 Porosity determination of shale by using Resistivity

For determine porosity in shale from resistivity weneed to define relationship between formation factor(F) and shale porosity. According to Archie (1942)formation factor define by:

w

o

RR

F ……………………….………………….....1.3

Where:oR : Resistivity of saturated rock

wR : Resistivity of the fluid saturating the rockAnd formation factor relate with formation porosity.Archie developed an empirical relationship (Eq.1.4)which is widely used. Table 1.1 summarized the usualvalues assumed by “a” and “m” for several types ofrocks.

m

aF

................................................................1.4

Where : a : Formation factor constant Φ : Porosity m : Cementation factorFormation factor equation has never been proposedfor shale, which reservoirs engineers have littleinterest in. only for shaly sand has been developed byWaxman and Smits in earlier 1968. However theycannot be applied to represent Shale behavior. Oneof the reasons is that clay particles are under porepressure conditions is shaly sands. The clay plateletstherefore behave approximately as colloids (Fig.1.6) and they are associated tobound water and free water as the dual-water model emphasizes [clavier et al,1977].


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Equation Application

2

81.0F

2

1F

15.2

62.0F

0,3to1,2

1F

Sand

Compacted formation, Chalks

Sucrosic Rocks

Olicastic Rocks

Table 1.1: usual formation factor expression [Schlumberger, 1987]

It’s assumed that a single fluid type couldbe in compacting smectite shale named“bound water”. There fore a new formationfactor relationship must introduce torepresent the electrical behavior of Shale.Perez-Rosales (1975) based onmathematical model for electricalconductivity which has been provided byFricke (1924), improved this newintroduction and defined the followingrelationship between formation factor andporosity:

2

3RR

Fw

o …………………………1.5

This expression of the formation factorderived from Fricke’s work could be usedin this form if shale could be actuallyassimilated to a suspension of a non-conductive solids sphere in a conductivefluid. This is not the case, however; andEq.5.5 must be modified to represent thegeometry of clay platelets and their highconcentration in the “suspension.” Pere-Rosales (1975) adapted Fricke’s work toporous media and obtained:

rw

o 1M1RR

F

…………………………….1.6


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Where: oR : Resistivity of the system

wR : Resistivity of the fluid M : Geometrical factor Φ : Porosity Φ r : Residual Porosity

“M” accounts for departures from the ideal spherical shape of the individual particles,and “Φ r ” is the part of the porosity that does not participate effectively in electricalconduction.1

In shale the saturating fluid is bound water, and the Eq.5.6 becomes:

1.0185.11

RR

Fw

Sh

…………………………..1.7

Where: ShR : Resistivity of Shale

wR : Resistivity of bound water M : (1.85=Geometrical factor by Perez-Rosales) Φ : Porosity Φ r : (0.1 =satisfactory for sand)

But none of the earlier approaches is representative of shale pore-water. Thisresearch argues that the bound water provides the electrical path in shale.thisrelation has been developed by Clavier (1977) as below:

By rearranging Eq.1.6 eventually yields shale porosity:

TR w …………………………………………….1.8Where: wR : Resistivity of bound water

β : Constant =297.6 T : Temperature ( o F)

And porosity of shale:

)1F(M)1F(M r

Sh

…………………………………1.9

And by using numerical value suggested by Perez-Rosales (1975):


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F85.0F1.075.1

Sh

……………………………………1.10

Thus shale porosity can be estimated from single shale resistivity measurement, andthe approximate knowledge of formation temperature. But represented method hasseveral limitations.

Limitation:

It is assumed that the Perez-Rosales (1975) Eq. provides a reliabledescription of the conductivity of porous media and that it can be adapted toshale.

The data presented by Clavier (1977) for sodium clay are assumed to berepresentative, and applicable to overpressure shale environments. ButKaiser (1984) has shown that the sodium is the preferred interlayer cationwith increasing temperature.

1.2.2 The Mechanical Module

As we have written before for mechanical module we need Terzaghi stressrelationship which is basis for pore pressure predication and pore pressure in thesimplest form is:

pvobtot,Z P

The compaction can be described by the second factor “Void ratio” which is definedas:

1

e ……………………………………………..1.11

Where:e : Void ratio : PorosityUsing the shale porosity estimates provided by the resistivity module, this equationcan be used to evaluate the associated effective vertical stress:

cCeie

v 10

………………………………………1.12

Where:v : Effective stress


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cC : Average Constant Compression index e : Void ratio

ie : Void ratio corresponded to v =1 psi

cC and ie are experimental dataneeded for this purpose were taken froma borehole stability study performed inthe north Sea by Despax(1988) and thisnumbers for shale are to:

ie =3.84

cC = -1.1

Thus Eq. 1.12 becomes:

1.184.3e

v 10

……………………1.13

Thus at the end we can estimate porepressure by reforming Eq.1.1 such:

vovpP …………………....1.14The summarize of whole steps is drown below:


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1.3 Estimation of porosity from Wireline logs:

1.3.1 Estimation of porosity from sonic logs

The sonic logging tool measured the sound wave transit time in a verticaldirection in the borehole. The porosity of the formation can be obtained from welllogs such as sonic and density. Their responses depend on formation porosity,fluid and matrix density. A commonly used linear relationship for estimatingporosity based on acoustic measurement was published by Wyllie (1956) asfollow:

mflp

11

…………………………………..1.15

Where:Ʋp : formation velocity

Ʋm : Matrix velocity

Ʋfl : fluid velocity

And in terms of transit times as:

mfl t)1(tt ……………………….….……1.16

And porosity estimation in shale can be calculated from:

mfl

msh tt

tt

……………………………..….…….1.17

200ttt268.1 m

sh

…………………………………..1.18

Where:

Δt : Formation transit travel time ([fts

] or [ms

])

Δt m : Matrix transit travel time (for Shale :Δt m = 47fts

or Δt m = 14, 32ms

) ]4[

Δt fl : Fluid transit travel time (Δt fl = 68, 8fts

or Δt fl = 226ms

) ]4[

Φsh : Shale porosity


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In the other hand Raiga-Clemenceau suggested other equation based on empiricalstudy of a very large dataset as follow:

x1

m

tt1

………………………………..…1.19

Where:

x : an exponent specific to the matrix lithology.

In (Fig.1.8) shows the comparing of these two methods for estimation of porosity!

1.3.2 Estimation of porosity fromdensity log.

The density tools measures thestrength of the diffused gammarays. The number of electron inatoms is approximatelyproportional to their density. Thuscollisions are therefore morenumerous the denser the material.Gamma ray attenuation is directlydepends on formation bulk density.If the density of the matrix isknown, porosity can be calculatedfrom:

flmb )1( ……1.20

Where:ρb : measured bulk

density

ρm : Matrix density

ρfl : fluid density


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And porosity for shale formation can be calculated from:

However the blind use of density logto estimate porosity in shale has alarge amount of uncertaintyassociated with it, as the matrixdensity of shale can vary over largerange. Typically density rangeestimation for shale is between 2.65

[ 3cmg ] and 2.70 [ 3cm

g ].

Shale is also a blanket term used todescribe a very large range ofquartz contents in rock (typically <40%).this also has heavily effects thegrain density of samples.(Fig 1.9) shows the variation inestimate of porosity from a densitylog using grain densities of

2.40[ 3cmg ] and 2.70 [ 3cm

g ].

flm

bmsh

………………..……….1.21


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1.3.3 Estimation of porosity from Resistivity log using Archie Eq. :

Porosity estimation from Resistivity log can be done by using the Archie Eq.(Rider, 1996) as follow:

m1

w

2wt

aRSR

………………………………1.22

Where: Rt : Formation resistivity

Rw : Pore water

Sw : Water saturation

a : Lithology constant

m : Lithology constant

The number of parameters that have to be estimated using this technique aid thereduction in accuracy of any porosity estimates that it produces.

The neutron log measures the hydrogen index of the rock surrounding the borehole.This can be quickly transferred into the porosity of the sand stones and carbonates,but the bounds water in clay structure gives an anomalously high estimate of shaleporosity (Rider, 1996). Since the amount of bound water in clays is variable, anyestimate of shale porosity using the neutron log is liable to be inaccurate.


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1.4 Summary and conclusion

The model developed in this study comprises two modules. An electrical module anda mechanical module. It is able to provide effective vertical stress estimates in shaleusing resistivity measurements and formation temperature. The equations necessaryto the interpretation were derived analytically, until calibration was needed to adjustthe ideal model to the real environment. This approach provides the user with bettercontrol and the possibility to calibrate the model rapidly in new environments. If anyof these methods are used with care and large numbers of calibration samples areavailable, they can provide fairly accurate estimates of porosity.Wireline log analysis is still one of the major methods employed to estimate porepressure. It is used to create models of pressure in offset wells during the planning ofdrilling programs. Many methods of pore pressure estimation, such as that fromResistivity, Sonic and Density logs, require many assumptions about the rockproperties, and so, unless copious of calibration data has been produced, theaccurate estimation of porosity from wireline logs is difficult.


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Part II:

Direct pressure measurement


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Chapter 2:

Direct Pressure Measurement Methods in Formation


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Introduction:

The Repeat Formation Test (RFT) and Drill Stem Test (DST) are an open hole wireline instrument primarily used for measuring vertical pressure distribution in reservoir,as well as for recovering formation fluid samples. The point by point reservoirpressure measurement technique is to used to determine the gradient of bothhydrostatic pressure of mud column in the bore hole before the tool is set or after thetools is retracted, and the formation pressure when the tool is set.RFT & DST alsoare a device capable of providing an estimate of formation permeability through theinterpretation of pretest pressure data recorded during downward and build -up. Theidea with any relation between RFT and shale pressure measurement may be able touse this test for shale which is among to permeable lags! And by measuring pressureon these lags my we can estimate formation pressure in shale too. An example forthis situation is deep water Sandston reservoirs which commonly observed to beisolated with shale dominated sequences. Pore pressure profiles through suchsequences are based on both direct measurements in the reservoirs, and estimationbased on porosity and shale properties in to non-reservoirs section. In this chapter abriefly review of the most useable direct pressure measurement and it will be tried toobtain relation between these two kinds of pressure measurements to estimate porepressure in shale!


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2. Direct measurement of permeable pore pressure:

The most direct pore pressure measurementsare made on porous and permeableformations! Two main methods are RepeatFormation Test (RFT) and Drill Stem Test(DST) which briefly have been present in thischapter.

2.1 RFT a briefly review:

2.1.1 The RFT Tool:

The repeat formation test tool has beendesigned to:

Measure Formation Test Collect Reservoir Fluid Samples.

Depth accuracy can be controlled by correlateda Gamma Ray curve or an SP curve with theOpen Hole loges. when the tool is set, a packermoves out one side, and back up pistons moveout on the opposite side, as seen in(Fig.2.1) the body of the tool is held away fromthe borehole wall to reduce the chances of the differential sticking.

2.1.2 Principle of RFT works:

When the tool is set, the pressure rises slightlybecause of the compression of mud cake by thepacker. Probe piston retracts and the pressuredrops due to the resulting flow line volumeexpansion and communication with the formation.When the piston stops, the pressure build up againbecause the packer is still continuing to compressthe mud cake until the tool is fully set. Next thepressure drops as the first 10 cc pretest pistonbinges moving at a constant rate. This time denotedas t 0 . After about 15 seconds the first pretest pistonreaches the end of its travel. At this time t 1 , thesecond piston begins moving at rate of 2, 5 timesfaster than the first piston movement, consequentlythe pressure drops further. When both pressurechambers are full, at time t 2 , the pressure builds uptowards a final pressure.


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The running times used for pressure analyses, Δt, is counted starting at t 2 .analysesof the build-up curve may yield permeability and reservoir pressure as withconventional drill stem and production pressure tests. Finally, after the tool isretracted, the mud column pressure is again measured. Fig.2.2 shows the RFTpretest and sampling Principle. A typical pressure recording is shown in Fig.2.3which shows both analog and digital pressure curves as standard log penetration.

2.1.3 Application of RFT

Besides the retrieval of formation fluid samples and measurement of the formationpressure, the RFT has found many applications in the field of reservoir engineering:

In exploration wells in unproduced fields In development wells

In exploration wells in unproduced fields it’s known that formation pressures mustconform to gravity capillary equilibrium establishing over time. Thus the conduct ofthe RFT survey and the interpretation of the data is governed by the concentrationthat the formation pressures lie on straight-line fluid gradients and the main objectiveof this testing is to delineate this gradient.


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In development wells, the observed formation pressures may already affect by eitherpartial depletion or possibility water injection. Thus the new development well is usedas an observation location at which the current state of the reservoir can bemeasured on a vertically distributed basis. The measured pressure profile reflects theresponse of the reservoir to production/injection and it is axiomatic that the pressureinformation may not be interpretated in terms of reservoir structure and fluiddistribution with out knowledge of the production which has taken place. Reservoirsimulation may often be the only possibility approach to interpret RFT data on a field-wide basis. ]6[

2.1.4 Limitation of RFT

The RFT tools provide accurate, definitive data on formation pore pressure.However, the formation pressure data can only be obtained from permeablelayers, such as reservoir sandstones or limestones. This formation maycontain pressures which bear no resemblance to the pore pressure in theoverlaying and underlaying formations, and such their application isrestricted to the formation sampled.

In HPHT wells the RFT tool should be considered for use prior toperforming potentially problematic drilling operations, such as coring, inorder to fine tune the required med density and minimize the risk of swab orsurge problems. ]5[

2.2 Drill Stem Test(DST)

DST is a method of the testing formation pressure and fluid. A drill stem with apacker is run and set just above the zone to be tested. The packer is set and a DSTvalve is opened to allow the reservoir to communicate with the inside of the drillstemwhich is run either empty or with a small calculated cushion.

The drill stem is run with several pressure gauges. The purpose of the pressuregauges is to record the downhole pressure during the sequence of flow and shut inperiods that comprise the DST. The pressures recorded during the test are used tocalculate reservoir characteristics such as formation pressure, permeability, skindamage and productivity index. Analysis of the pressure build up from shut in leadsto accurate determination of the formation pore pressure. The second shut-in periodis used for determining the final shut-in reservoir pressure. The actual static reservoirpressure is determined from Horner analyses of the DST pressure data.

2.2.1: Limitation of the DST

Data from drill stem tests enable accurate determination of the reservoir pressure.However, the pressure data can only be obtained from permeable formations thatexhibit sufficient hydrocarbon reservoir potential to warrant the expense of the DST.As with RFT pressure data, the reservoir pressure calculated from the DST may, ormay not be the same as the pore pressure in the adjacent formations. ]5[


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2.3 RFT and estimation of pressure in shale

As we know RFT is used for direct pressure measurement in permeable layers. Inshale as an impermeable layer we can not used RFT or we get any data from RFTtools during passing shale layers. But in some case we take RFT data to estimateFormation pressure in shale! In some case we have two permeable layers upper anddowner the shale layers and with using RFT data from this permeate layers withcontinuing sketch of these points we may estimate pore pressure in shale! But thisgives a big uncertainty to us and for solve this problem and decreasing uncertaintywe can use other SWD tools as VSP data with RFT data. (Fig. 2.4) shows a principleof this method which have been done already in Nile Delta in Egypt byMann & Mackenzie (1990).

However direct data (RFT, MDT, FMT, DST) in the shale as impermeability’s layers,are too low to take samples; therefore, overpressures in shale can be calculated fromusing pressures recorded in isolated sands or just use pressures in isolated sandsdirectly to establish regional shale pressure gradients.


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2.4 Summary of the pressure determination

When collecting pore pressure data for a new well, it imperative to label the datapoints according to source used to measure or calculated them. Hence that the datamay come from mud logging, LWD or RFT and DST sources. Obviously the RFT andDST pressure data are the most definitive and have the least uncertainty associatedwith them. Mud program and casing seat selection can therefore be based on RFTand DST pore pressure values.

While the RFT and DST data provide definitive values of pore pressure for thewell, the direct measurements are only possible in permeable formations andare obtained after the well is drilled.

They are also not applicable to the surrounding, largely impermeable, shale sectionswhere the majority of the overpressure is developed.

Estimation and calculating of pore pressure from mud logging, wireline and drillinglog data are restricted slowly to the Shale sections. Establishing a normal compactiontrendline is important when calculating pore pressure from log derived shaleproperties. Among the several of the available well logs, sonic log data is consideredto be the most accurate, as it is largely unaffected by borehole size, formationtemperature and pore water salinity.


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Chapter 3

Direct measure Pressure in Shale :( MESPOSH)


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Introduction:

Direct pore pressure in shale is one of the greatest progressive step changes indevelopment of pore pressure determination ahead of the drilling bit. The lack ofdirect pore pressure measurement is preventing improvement of borehole stabilityassessment and seismic interpretation.This method not yet done in the petroleum industry, it is documented that long termpore pressure measurement in shale is feasible with existing equipment. The reviewindicates that short term measurement of pore pressure is not possible with currenttechnology. It seems new equipment and technology must be developed. Guidelinesfor such development have been established but this technique may have aconsiderable cost. Thus it’s proposed to lunch a JIP on pore pressure measurementin shale, so evaluate of main influencing factor on pore pressure measurement inshale has been performed. Therefore the pore pressure effect of local stressconcentrations around a hole needs to be dissipated; and such dissipation for a porepressure sensor placed at the wall of a standard well may takes a long time (weeksor month!).For short terms application a small size hole may be necessary to get ameasurement with in a reasonable time for a drilling operation.The major task for measuring of pore pressure is identified as Zonal isolation. Weknow that the permeability of a sealing cement may be one magnitude or higher thanshale without disturbing the measurement too much. However the major concern stillis avoiding channeling or micro annulus.Sensors at various levels are recommended to verify proper sealing.

A principal challenge for long term measurement is to develop suitable proceduresfor installing the instruments.

The main objective is to develop a system for reliable and economical pore pressuremeasurement in shale and to verify the system by a field trial. On long term the porepressure measurement in shale is a starting point for predication of the pore pressurea head of the drilling bit.Most of drilling and seismic travel time takes place in shale and it is dominatingsealing material for hydrocarbon reservoirs. Understanding the shale behavior isnecessary for reducing cost of drilling, reliable interpretation of seismic and forassessment of the interaction between the reservoir and surroundings rocks. Theroles of Pore pressure in shale may describe as:

1. Pore pressure has a direct impact on drilling safety and further exploration, inover pressure zones.

2. Pore pressure is important as total stress to determine effective stress. Theeffective stress controls the mechanical behavior of geomaterial as strengthand stiffness. Both stability of well bore and seismic velocity are realization ofthis mechanical behavior.

3. Pore pressure controls hydraulic gradient, which controls fluid flow in a basin.

This issue is very important and it’s strange that there aren’t any reports of directmeasurement of pore pressure on shale in the petroleum industry. Thus porepressure in shale is one of the last items on the list of primary mechanicalparameters. Thus “It’s time to do something about It.” to enable progress for holestability assessment, seismic interpretation and fluid flow models.


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3.1 Application:

Several applications for MESPOSH are:

► First application of direct pressure measurement in shale is calibrating theexisting indirect methods. Thus various geological settings should beinvestigated and depth variation should be checked. So long termmeasurement techniques are sufficient for this kind of application. It isconsidered the most simple and reliable approach.

► Measurement in exploration and appraisal wells to speed up the learningcurve in new areas and thereby create added value to drilling and explorationrisking

►If short terms equipment become available, it would open up for applicationin exploration and appraisal wells to speed up the learning curve in new areasand so create large values in terms of more efficient drilling and reducedexploration uncertainty.

►there is additional application of MESPOSH which is when shale is near orwithin reservoirs with serves depletion, for instance HPHT fields. Productionrelated pore pressure changes in such zones are important for drilling indepleted reservoir and also for new technologies such as 4D survey incombination with aeromechanical modeling.

►Tight reservoir

3.2 Existing Techniques:

3.2.1 Pore pressure measurement in petroleum industry:

Direct measurement of pore pressure in oil industry is made in permeable reservoirzones and this pressure is called reservoir pressure. This method is done duringdrilling or in a completed well. During drilling the pore pressure is observed by porepressure equilibration or transients in a sealed part of the borehole. In a completedwell pressure sensors measured the fluid pressure continuously, either with inproduction tubing or direct contact with formation. Periods with production stop givesa measure of the reservoir pressure (no draw down).

Pore pressure in shale is estimated currently by following methods:

As a part of basin modeling. By calibration of seismic velocity. By calibration of electrical loges. From pore pressure measurement in permeable layers with in the shale

sediment. Observation of inflow during drilling. ]10[


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3.3.2 Limitations of this method:

Method 1 is a prognosis in need of verification. Methods 2&3 have a problem with the basis for the correlation. Too few data points in method 4. Method 5 suffers from the low permeability of the shale. ]10[

Pore pressure measurement in clay is a common activity in foundation design andgeotechnics pressure measurements. Normally this is done on long term basis bydedicated borehole with one or more pressure sensors in contact with clay and withhydraulic isolation a long the well. Also short term measurement with smallpiezoelectric penetrated into clay is used.

3.3 Basic Principle:

General:

To obtain pore pressure in shale three requirements must be in place:

A pressure sensor communicating with the pore fluid of the shale. Eliminate or manage the disturbance from installing the sensor. Eliminate or manage disturbance during the measurement.

The disturbance from installation of the sensor may have the following sources:

Concentration of local stress from penetration or drilling of a hole Chemical and Temperature effect from the wellbore fluid during drilling Pore pressure excess from wellbore fluid during drilling Cement Sealing

Unintended pressure communication is the main source of disturbance duringthe measurement of pore pressure. A typical problem of this kind is insufficientcement seal along the wellbore. Heating and water absorption duringhardening of cement are other possibility disturbance during drilling.Temperature variations due to the production flow also may disturb themeasurement, if the sensor is placed in a producer.

3.3.1 Chemical and Temperature effect:

Assuming dissipation’s effect of local stress also accounts for temperature andchemical effects in the wellbore during drilling time. Thus fluid chemistry and fluidtemperature (if it’s possible) should be designed to minimize this effect. However, thetemperature effect of the production flow is more severe concern for long termmeasurement in the producing well. If flow and flow temperature are constant, theeffect of the pore pressure will reduce with increasing time. But in reality thetemperature effect will vary. This disturbance needs to be managed by combinationof modeling and temperature measurement. As temperature is an issue in bothproducing and non produces wells, pore pressure measurement should always beaccompanied by measurement of temperature.


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3.3.2 Pore pressure excess from wellbore fluid during drilling:

In drilling with WBM (water based mud) dissipation of pressure during drilling in shaleis possible. Such dissipation would give excess pore pressure relative to the in situpore pressure. This effect may be significant. Time exposure is more important thanthe hole size. For a week time demonstration which is not uncommon for a wellsection, effect on borehole wall takes longer to dissipate then the local stressconcentrations. Influence depth also becomes significant for one week timedemonstration.

Error handling:

Eliminate the effect by waiting until the effect is dissipated (may takesmonths).

Effect managing by modeling the transient pressure as in well testing, mustalso include the effect of local stress concentration.

Minimizing effect by short demonstrated time or rapid penetration,particularly relevant for short term measurement.

Thus, using of OBM (oil based mud) may be an alternative to avoid excess porepressure during drilling well. But it must be ensure that the capillary effect of oilbased mud does not prevent contact between the pore pressure sensor andformation. ]10[

3.3.3 Cement sealing:

Traditionally the cement which sealing a pore pressure sensor should haspermeability equal or less than formation. Vaughan in (1969) indicated that thepermeability of the cement in a geotechnical piozometer string may be stringsignificantly lager than the permeability of clay without disturbing the porepressure measurement too much. ]10[

Pore pressure measurement due to cemented annulus communication dependson the following factors:

► Cement-shale relative permeability► Geometric relationship between two flow areas:

Flow area of the cemented annulus outside the well. Flow area between pore pressure sensor and shale formation.

Parameters which control this flow area are annulus radiuses(inside and outside) and length of pore pressure zones.Practically results confirm that cement’s permeability may be larger then shale’spermeability without giving a considerable error. In the large contact area betweenshale and sensor, this error is less than 1% even cement’s permeability is 300times bigger than shale’s permeability.


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This means that the nominal cement permeability as used today is enough forreasonable pore pressure measurement in shale. But the main problem here isassociated channel in cement. Such channels may appear from bad cementingjob or long term effects from a micro annulus created by shrinkage during cementhardening. Such channeling is probably not uncommon. Installation of porepressure sensor in different parts of drilling levels for evaluating of the possibleerrors from cement seal should be helpful.

3.4 Measurement methods:

Overview

Generally Short term and long term measurements are two methods for measuringpore pressure in shale from existing pore pressure measurement methods. Anoverview of the options based on this distinction is given in Fig 3.1 and Fig.3.2Schematic illustration of the options.


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3.4.1 Short Term Measurement:

Short term measurement is mad by drillstring during drilling time or by wireline inopen or closed hole. Sidewall pore pressureis greatly affected by local stress and byfluid pressure unless OBM is used. Formore accuracy it’s possible to drive the insitu pore pressure from early timedevelopment of the sidewall based on adissipation model. Use of OBM mayimprove such measurement if the testpenetrates a bit into the formation. Theaccuracy of this method is low and evenworth while to check out as similarequipment already exists for application inpermeable zones. In this method drill stringmust stop (avoid of drillstring movement).For fixed drilling’s units are no problem butits need to be addressed when drilling is ona flouting unit. The most reliable short term


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measurement will be in penetration of small hole with a function similar to thepiozoprobe in geochemical application.

Such penetration could be mad laterally through the bore hole wall or axially at thebottom of the hole. As we discussed before a dissipation time of minutes or a coupleof hours could be sufficient for dissipation of the local stress if the hole diameter isnot more then 5 mm. ]10[ The effect of well bore pressure would not be concern in thiscase. Clay allows penetration with out drilling thus clay is an ensure sealing. In Shaleboth drilling and sealing device would be required .drill string movement duringmeasurement would be concern for this option and for borehole wall measurement.

The most realistic option for short term measurement may be a compromise betweena sidewall device and a deep penetration test. That means a semi deep penetrationbeing practically possible with disturbance manageable by means of transientmodeling. At the qualification stage a short term method should in any case beverified by more reliable long term measurement. ]10[

3.4.2 Long Term Measurement:

Dedicated well/Sidetrack

The most robust and accurate example of long term pressure measurement is porepressure measuring in a deviated or sidetrack borehole. Existing equipment may beused. An open hole well is the simplest solution. A string and sensors may be usedand conventional cement sealing would normally be sufficient. If the sensor issurrounded by cementing, in many cases it would not be a problem.

An alternative for that is to place sensor inside the casing. The sensor must besealed with packers inside the casing and by the same time communicate with theformation, for inside through perforations. Sensors at several levels to confirmsealing are recommended.

Abandoned well/sidetrack

An abandoned producing well or sidetrack may be utilized for pore pressuremeasurement. With respect to cost this is an alternative option and it still avoidsconflict with other functions. But the long term integrity of the sealing cement is aparticular concern in this case. It may also necessary to address some formalitieswith respect to final abandonment. A sensor inside the casing would be the moststraight forward measurement which it would be sealed internally by packers andcommunicating with the outside formation through perforations. Inside the casingcombination with cement seal can be used and in this case sensors at different levelswould be available to verify the seals.Putting sensor outside the casing and then plug the casing is the other measurementoption to drill through the casing. Schlumberger’s Cased Hole Dynamic tester orsimilar may be applied. Signal transfer through the casing appears to be missing forthis option and its need for equipment development is thereby likely.


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New producer/sidetrack

The possibility of measurement at a site of current interest would be increase if weuse a new producer in stead of an abandoned well. It would allow design fromscratch but it also introduces conflicts with other functions. The conflicts may belimitation of space, barrier requirements and restriction on signal transfer. In addition,the temperature effect of the time from drilling to production is sufficient to allow apore pressure measurement before the production is started. Also in this case themain options are to place the sensor inside or outside of casing. Both options areapplicable with current equipment.

3.5 Challenges:

1. A principal challenge for Long Term measurement is to develop suitableprocedures for installing the instruments.

2. Short Term measurement of pore pressure is dependent on technologydevelopment. An attempt to describe the most important elements of suchdevelopment is given in section 3.4.1of these elements is small diameterdrilling.

3. Another technology which should be considered to get sidewall penetration forshort term pore pressure measurement is the existing rotary sidewall coringmethod.

For both short term and long term application it is advisable to collect thestandard log used for pore pressure interpretation to calibrate the existing indirectmethods.


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Part III:

Indirect Pressure Measurement


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Chapter 4:Seismic While Drilling (SWD)


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Introduction

Geophysical methods in combine with other tools, can predict the reservoir pressurein many cases. Overpressure shale can act as good reservoir seals, but can alsocause drilling difficulties, particularly in maintaining safety margin for drilling mudweight. Geophysical techniques are based on the impact of reservoir pressure on theseismic velocities (primarily Compressional waves).Many studies have demonstratedthe effectiveness of geophysical methods for pore pressure predication. One of thefirst of these studies has been published on earlier 1968 by Pennebaker.However Geophysicists published geopressure (Dutta, 1987) that include majorgeophysics-related methods for pore pressure predication (See table 4).The new technology improvement of 3D seismic and more recently 4D seismic, it hasbecome possible to make pore pressure predications more reliable and create three-dimensional pressure profiles. Seismic while drilling (SWD) is the seismic techniquesoperated while the drilling is lowered in the borehole, during effective drilling or whileconnecting drill pipes. In the past 24years (1986-20009) ,the drill- bit SWD techniquepracticed by the industry utilized the acoustic energy radiated by the Tri-Cone bit toprovide the real time information during drilling by providing time-to-depth and look-ahead information. Another emerging technique which is being used mainly bySchlumberger since 2000 is Vertical Seismic Profile While Drilling (WSP-WD), whichconsists in recording the seismic signal generated by a surface seismic source onseismic sensors integrated inside the downhole borehole assembly (BHA). In thischapter it has been tried to give a present day picture of the SWD techniques briefly.


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SWD can be subdivided on several methods as below which we tried to describeeach method briefly:

1- Drill Bit Seismic2- Vertical Seismic Profiling While Drilling (VSP-WD)3- SWD using Swept Impulse Source4- Coil Tubing SWD5- New Concepts for SWD

4.1 Seismic While Drilling Operation and Application

Even thought the SWD tool is coupled to BHA like a standard tool but its operationand set up is far from standard. For making this service as a powerful drilling decisiontool, a proper planning ahead and a proper understanding of the full potential of thedata will be necessary. SWD has the potential of the producing a real time update tothe geological model. It offers improved resolution and more accuracy of depthconversion. Its flexibility of source / receiver positioning several other geophysicalapplications will be possible (i.e. salt flank & fault plane). SWD service has thepotential of becoming a key drilling decision tool. Uncertainties in data qualitycoupled with surface seismic limitations leads to risk management process. Thisneeds to a good understanding of workflow of seismic processing and reservoirproperties to minimize time for data preparations prior to evaluation and decisions.

SWD can be done in two path method:

Normal ray path (source on surface and receivers in the borehole “BHA” i.e.Halliburton model)

Reveres ray path (source in the hole and receivers on surface)

SWD needs a quiet environment and for performing this quiet environment standarddrilling activities must be stopped including mud pumps! This will be done during thestand changing! A stand change takes some time (2-10 minutes) which is enough for3 to5 shots to be fired! It’s however too short time to reposition the source withcurrent technology. The source position is an alternative for future! But its locationcan be either on rig or seabed or a boat connected source.Vertical Seismic Profiling (VSP) is a technology which makes better the surfaceseismic resolutions. It is great risk to do drilling campaign based on only surfaceseismic but VSP reduces these risks! In VSP data will be available in time beforereservoir zone is approached. As the earlier data is available the bigger impact thedata will have on the risk reduction. Getting the VSP data and availability on time duedrilling is the important issue for the SWD solution.


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4.1.1 Planning phase

Design of the SWD is one of the first step for successfully utilize its full potential. Thiscould be as follow: ]12[

Planning

Ray trace modeling Real time processing Acquisition density Site survey Rig setup Drilling personal training

Operation

Source handling Network/application performance Decision making process/resources

4.1.2 System design and Consideration

SWD contains:

main surface computer surface control box seismic source controllers seismic sources down hole tool

Seismic sources and controllers are standard. (Fig.4.1) shows the mainsystem design. In order to design a borehole seismic survey to meet specifictarget objectives, it is necessary to model the seismic response of the earthnear the borehole. A perfect design process would take into consideration allavailable data, including but not limited to:

A. geological structure and stratigraphyB. characteristic surface seismic waveformsC. The local P&S-velosity fields, including well VSP data and seismic processing

and migration velocity cubes.D. Local and area well information, including multi-pole sonic and density logs.


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While many SWD projects include well path-on seismic mapping objectives, itis becoming increasing desirable to perform wave form processing of SWDdata in order to image and detect certain targets ahead of the projected wellpath. In order to support these design objectives, it is necessary to modelwave fields and amplitude distributions in 3D using wave-front ray tracing andfinite different modeling tools. These tools have been specifically designed forthe borehole to include all aspects of borehole and source geometries whileaccounting for diffractions, anisotropy, and converted waves. ]12[


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4.1.3 SWD Tool

The SWD tool contains 4 geophones, 8 accelerometersof which 4 are external and 4 internal and 4 hydrophonesthat can be configured and mounted for operation in anyof the three principal axes. 12 of the sensors are exposedto the borehole annulus. ]12[

The sensors are mounted such that they are passivelycoupled to the surface and structure of the interest in thewell, and they are robust enough to withstand theviberation, temperature and pressure conditions that thetool will experience while drilling. The geophones and theexternal accelerometer are coupled with the collar. Thehydrophones are exposed to the well fluid. The sensorsare designed to withstand temperature up to 165ºC andpressures of 25,000psi in all directions. Fig.4.2 showssensor positions on SWD tools.

4.1.4: Process of SWD

The system direct measurement of seismic travel timesfrom surface to the survey locations along the well bore.Data are used to track the bits on the original surface seismic images used to planthe well. In addition section of the stocked waveforms used for check-shut and incertain circumstances can also provide a limited image many hundreds feet a headof the bit. The information gathered will be used to steer the well, set casing points,and avoid drilling hazard. The tool has a processor and memory and receives itsseismic energy from a surface seismic source an air gun array located on either therig or source vessel offshore or a viberator or dynamite shot on land. Afteracquisition, the signals are stored and processed, and check-shot data and qualityindicators are transmitted uphole in real time by mud-pulse telemetry.

The time –depth data are used to position the well on the seismic map, andwaveforms can now also be sent uphole in real time. All of the raw recordedwaveforms are stored in memory for processing after the tool gets back to thesurface. One of the key advantages of the tool is that it dose not interfere with thedrilling process, and it doesn’t require any extra rig time. Fig.4.3 & Fig. 4.4 showschematic of SWD process in a simple way.


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4.1.5 SWD Application

Sub-Seismic fault imaging Overpressure detection Reducing Rig-Time It can be often only way to collect data in much deviated wells or the

wells with stability issues while wire line tool are difficult or non-economical to run.


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4.2 Drill-Bit Seismic

Two types of Drill-Bit Seismic:

A. conventional Drill-Bit Seismic

The drill bit seismic method delivers seismic time-to-depth and look ahead seismicimages of the formation ahead of the bit. It does this in real-time, allowing timely inputto the drilling process. The data and images are available at the well site, or can betransmitted back to town. Only surface sensors are used to acquire the data,avoiding the high costs and potential risks associated with downhole tools. No rigtime is required, and the technique does not interfere with the drilling process. ]13[

4.2.1 Application:

The information obtained from drill bit seismic surveys can be used for a number ofapplications, some of which are listed below:

1. Locating on the Bit.2. Look Ahead Imaging3. Casing/Coring Point Selection.4. Pore Pressure at the Bit.5. Pore Pressure Ahead of the Bit.6. Depth-to-Hazard Prediction.

4.2.2 Procedure technique

The basic concept behind drill bit seismic is verysimple. It uses the acoustic energy radiated by aworking drill bit to determine the seismic time-to-depth as the well is being drilled. The energyneeds for drilling is supplied to the bit by rotationof the drillstring, if a rollercone bit is used; thisrotation causes the cones to roll over the bottomof the hole. As the cones roll over, the teethpenetrate and dig the formation, destroying therock. As each tooth indents the formation itapplies an axial force to the bottom of the hole,and an equal and opposite force to the drillstring.

The succession of axial impacts as the bit drillsradiates compressional or P-waves into the


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formation, and causes axial vibrations to travel up the drillstring. A working rollerconebit acts as a dipole source for P-waves radiating energy upwards towards thesurface, and downwards ahead of the bit (FIG4.5). At the surface geophones,hydrophones, or a combination of both are used to detect the P-waves. Sensors,such as accelerometers, placed near the top of the drillstring (on the swivel or topdrive) detect the axial vibrations traveling up the drillpipe. Although the bit generatedsignal can be detected, it is continuous in nature. Since the fundamental drill bitseismic measurement is time-to-depth, timing information must be extracted. Ingeneral, the energy propagating through the formation travels more slowly than theaxial vibrations in the drillstring. The seismic sensor signal therefore contains a timeshifted version of the drillstring sensor signal.

Correlating the drillstring sensorsignal with the seismic sensorsignals, a technique patented byElf in1985, helps to determine thisdifference in travel time ΔT re (seeFIG.4.6). Once ΔT re is known, ifthe time taken for the axialvibrations to travel along thedrillstring, ΔT ds can be determined,the absolute travel time from bit tosurface, and, ΔT f can becalculated. The time-to-depth iscalculated using the direct radiationfrom the drill bit. The energy thatpropagates downwards ahead ofthe bit is often reflected back to thesurface by impedance changes inthe formation. This energy can alsobe detected, and processed toproduce a seismic image of theformation ahead of the bit. Whenused in combination with thesurface seismic, such “look ahead”images allow the approach tocritical horizons to be monitored asdrilling progresses. The aboveexplanation is rather simplistic. Inpractice there are significantdifficulties that must be overcomebefore useful information can beobtained. ]14[


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B. Drill-Bit Seismic with Shock Absorber and EMWD

First time it has been used by drillers in order to collect downhole data by IFP, aFrance company in 1991 with an MWD field test in eastern France Gaz De Francewell. They used real-time field evaluation of the seismic signal generated by Drill-Bit.as result, the first minutes of drill-bit seismic data correlated either by the downholeaccelerometer or by the top of drillstring accelerometer did not show a bigdifferences, as both correlated records were altered by a high level of drillstringmultiples. The main improvement obtained by correlation with the downholeaccelerometer was a higher frequency content. IFP field geophysics’ felt that it wouldbe desirable to introduce a mechanical decoupling device above the drill bit anddownhole sensor, in order to reduce the generation of the drillstring multiples and allsorts of associated secondary seismic source effects related to presence of thedrillstring. This kind of damping element is well known by the drillers as a “shockAbsorber” and had been developed by the drilling equipment manufactures duringthe period 1950-1985. the concept was quite feasible because drill-bit vibrations arepowerful enough to generate long range seismic signal from the bit to the surface.the signal to noise ratio improved after using shock sub despite the fact that thepresence of shock sub reduced the peak amplitude up to 80 %. ]14[

4.2.3 Advantage drill-bit seismic

The drill bit seismic techniques provides useful real-time information. When used inconjunction with other information it can help to:

Locating the bit on the seismic section Optimizing casing and coring points Reducing the number of casing Pore pressure estimating at the bit Predication of pore pressure ahead of the bit Predication of the depth to drilling hazard No more rig-time activities and risks and more drilling operation costs.

4.2.4 Limitation drill-bit seismic

In soft rocks and large depth (above 18,000 ft) and in horizontal wellsthis technology is unreliable!

In high deviated wells it cannot be used. It can only work reliably when drilling with rollercone Bit. Not with PDC Bits.


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4.3 Vertical Seismic Profiling While Drilling (VSP-WD)

VSP-MD is a transfer of wireline borehole seismic to drillingoperations for drilling and real time operationsbenefits(Fig.4.7). VSP-MD is almost identical to wirelineservice using the same surface source and downhole sensors.The main difrence is ,there is no directe cable connectionbetween tool and surface. This technique use a downholesensor in connection with BHA which receives seismic energyfrom sources which is coming from a source vessel (rig orboat).The source is fired while making the drill stringconnection or drilling and mud circulation stopped, to preventthe effect of drilling noises on data acquisition process. Theseismic energy can be produce by a source as air-gun onoffshore or dynamite on onshore and receives by VSP-WDtool. This tool can collect both the directed and reflectedseismic signals. The VSP-MD tool can store a raw full-waveform data in the downhole memoray storage which culdbe sendback later during tripping of the bit. Seismic signalsare recorded both directly from the source and reflected fromformations to be imaged.these signals are stored in toolmemory for later processing. Immediately after obtainning thedata,downhole processing determines the check-shot time. Acomplet procedure of the tool is shown in Fig. 4.8 .

The real-time relationship is used to locate the bit on thesurface seismic image and this enables to forward drillingdecision. Only the most important data will be transferreduphole, the rest data will be stored in donwnhole tool memory.When the drill string is pull out of the hole, waveform data canbe downloaded from tool memory and then send them to aprocessing center for VSP image processing. This techniquedepends on the geometry of the well and the source location.Vertical wells with zero offset sources are best fitted for thismethod.

4.3.1 Advantage of VSP-MD

In horizontal wells VSP-WD seems is the only alternativefor more well instability and security.

It places the bit on the seismic map or section. Animportant result of correction of the seismic down to bitposition is that the seismic uncertainty ahead of the bit isreduced. Uncertainty will be reduced from 700 m to 10 m.


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While coring operations well can bedrilled very close to the interface wherethe core is needed. This eliminates alarge amount of unnecessary hole thatneeds to be drilled. Thus avoidingreduced or missed core data and savingtime as well as money.

Large saving can be realized usingVSP- WD service. It saved cost ofrunning wire line VSP which was not apreferred option due drilling.

since the bit can be seen on the seismicmap in real time the driller can drill thewell very close to events seen on theseismic map and place the casing veryclose to where they ideally should beset.

It allows early predication of potentialpore pressure anomalies and it can efficiently assist salt proximity surveys.

4.3.2 Limitation of VSP- MD

It’s claimed that it provides look –ahead imaging, however the rangeand accuracy of this capability is stillnot accurately known.

Mud pulse telemetry of processedvelocity is planned but not presentlycommercial.

The biggest limitation of VSP-WDservices is to ensure a goodmechanical coupling of the VSPseismic sensor with the borehole andhigh precision required on downholeclock


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4.4 SWD using Swept Impulse Source

Seismic profiling using impulse hydraulic tool is the new method in SWDtechniques. The tool has capability of generating a broadband seismic signal atbit due drilling. This method overcomes the limitation of Drill-Bit Seismictechnique. For example can be used in soft formation and inclined holes withPDC bits. This method provides real -time reverse seismic profile while drillingand high resolution look a head imaging while drilling (Fig4.9). It can be used inboth vertical and deviated wells by using its independent compression and sharewave source. It also helps to give early warning of gas kicks. Seismic profiling andimaging could be taken out without stopping normal drilling operation and withouta downhole motor. This method was tested successfully by Baker Hughes.


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4.4.1 Seismic profiling using Swept Impulse Tool (SIT)

Different test shows that the hydraulic pulse tool has good signal propagation tothe surface over a depth of 2700 ft. This method will be available on both verticaland deviated wells. The tool produces a strong shear wave while drilling but whendrilling is stopping, it will be not generated any share waves. This ability allowsprofiling of both P- Waves and S-waves velocities with direct application to poregas detection. A little free gas presentation at the bit will immediately eliminate theseismic signal to give early warning of gas kick. The Swept Impulse Sourceincorporates a hydraulic pulse valve. It consists of a mechanism which varies theduration in between two pulses. Sweeping the cycle rate allows Seismic profilingand high resolution look ahead imaging while drilling using a technique similar toswept impact seismic profiling.

4.4.2 Advantage of Swept Impulse Tool

True real-time seismic while drilling Reverse vertical seismic profiling for depth correction Pore-pressure detection High-resolution look ahead imaging due drilling Independent compression and shear wave source Early warning gas kick detection Vertical or inclined wells Cross-well surveys

4.4.3 Limitations:

Communication between different personnel groups in a drilling process. Bad weather and big water wave limited gun operations The EX-rating of the cables and its layout Drilling time increasing is high risk for SWD Operation(example from 19 to 43

days) High cost in special deviated wells


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Chapter 5:

MWD/LWD


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Introduction:

MWD/LWD is a system which we can get a wide variety of directional steering,formation evaluation, geosteering and drilling efficiency applications. Thesemeasured while drilling data are in real time and recorded modes at the well site andcan be transmitted directly to office-based computer systems. In addition, the MWDdata can be available anywhere in the world in real time due to a secure internetconnection.MWD/LWD design allows the tool string to be configured with virtually anycombination of sensors to meet specific application and BHA design requirements.Three different real-time telemetry systems (positive mud pulse, negative mud pulse

and electromagnetic) are available to make dependable real-time data under a widerange of drilling conditions and with type of drilling fluid.

Real-time data transmission is supplemented by recording data in downhole memoryfor retrieval after each bit run.The suck, vibration and heat of downhole drilling environment make survival of anyelectronic instrument difficult. MWD provides geometrical information on the positionand helps to drill the well safely and efficiently. Measure While Drilling (MWD) ismeasuring and getting of directional data form wellbore, pressure in the wellbore anddrilling dynamics measurement such as vibration and shock. But Logging WhileDrilling (LWD) is logging of the properties of the formation and reservoir fluids whiledrilling and before drilling fluids invade the formation, similar to open-hole, wire linelogs. The most frequently used measurements include Gama Ray, Resistivity,Density, Porosity, Acoustic travel time and Formation pore pressure.In this paper we discuses MWD/LWD briefly related to pressure predication anddetection in formation and shale.


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5.1 Measurement while drilling (MWD):

MWD is a system to make drilling measurements and transmit data to the surfacewhile drilling the well. MWD tools are as part of BHA. The tools are either containedinside a drill collar (sonde type) or are built into the collars themselves. Themeasurements of GR, directional survey, tool face, pressure in borehole,temperature, vibration, shock, torque etc can be taken by MWD. Some advancedMWD tools can even measure formation pressure and take formation samples. TheMWD also provides the telemetry for operating rotary steering tools (RST). Themeasured results can be stored in MWD tools and the results transmit digitally tosurface using mud pulsar telemetry or other advanced technology. MWD systemshave the capability of receiving control commands which can be sent by turning onand off mud pumps or by changing the rotation speed of drill pipe or by otheradvanced telemetry technology such as wired pipe.

5.1.1 Types of transmitted information:

5.1.2 Directional information

Taking directional surveys in real time is one of MWD tools capabilities. MWD toolsare generally capable of taking directional surveys in real time. Accelerometers andmagnetometers to measure the inclination and azimuth of the wellbore at certainlocation can be used by these tools, and then they transmit data to the surface.A series of surveys at some intervals of the well bore (anywhere from every 30 ft (i.e.10 m) to every 500 ft can be calculated.MWD tools are extremely complex pieces of high- tech electronics. This informationfrom MWD allows operators company to prove that their well does not cross intoareas that they are not authorized to drill. However, they are not generally used on vertical wells, due to the cost of MWDsystems.’’ Instead, the wells are surveyed after drilling through the use of MultishotSurveying Tools lowered into the drillstring on slickline or wireline.” ]22[

Directional Drilling is the primary use of real-time surveys. Because the Driller mustknow where the well is going and he must steer the well towards target zone. MWDtools also generally provide tool face measurements to aid in directional drilling usingdownhole mud motors with bent subs or bent housings.


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5.1.3 Drilling mechanics information

MWD tools can also provide information about the conditions at the drill bit. This mayinclude:

Rotational speed of the drillstring Smoothness of that rotation Type and severity of any vibration downhole Downhole temperature Torque and Weight on Bit, measured near the drill bit Mud flow volume

Use of this information can allow the operator to drill the well more efficiently, and toensure that the MWD tool and any other downhole tools, such as Mud Motors, RotarySteerable Systems, and LWD tools, are operated within their technical specificationsto prevent tool failure. This information also is valuable to Geologists responsible forthe well information about the formation which is being drilled. ]18[

5.1.4 Formation properties

Many of MWD tools can take formation properties measurements. At surface thismeasured data can converted to loges as same as wireline logging. The MWD toolallows these measurements to be taken and evaluated while the well is being drilled.This information makes it possible to perform Geosteering, or Directional Drillingbased on measured formation properties, rather than simply drilling into a target.

“Most MWD tools contain an internal Gamma Ray sensor to measure natural GammaRay values. This is because these sensors are compact, inexpensive, reliable, andcan take measurements through unmodified drill collars. Other measurements oftenrequire separate Logging While Drilling tools, which communicate with the MWDtools downhole through internal wires. ]18[

5.2 Data transmission methods:

5.2.1 Mud pulse telemetry

This method is most used method for transmitting data from measurement tools inthe borehole up to surface on rig. Due drilling time, mud will be pumped fromsurface down through drill string and of course through the measurement andlogging tools (MWD/LWD), then through the drill bit and back to the surfacethrough the ring-room between the drill string and formation. The increasing innumber of measurements puts a higher demand on data transmission speed.Mud pulse telemetry is limited with regard to bandwidth and can only 10-48 bitspr/sec data transmission. To maximize the real-time value from the advancedmeasurements we will need kilo-bps capacity. The newly introduced wire drillpipecan obtained this capacity.This test has been done by several companies in North Sea.


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This technology is available in three varieties:

Positive Pulse Negative Pulse Continuous Wave

5.2.2 Positive PulseThis system causes a periodic, partial restriction of thedrilling fluid inside the MWD collar.The speed of transmission is between 4000 - 5000 ft/sec inthe drilling fluid. The positive pulse system is low costwhen compared to hardwire systems, and no special rigmodifications are necessary. It has the added advantagebecause it is not affected by LCM. The system does have aslow data rate and is limited to a digital encoding scheme.This type of system is used by Eastman-Teleco, SmithDatadril, Speery- Sun and Western Atlas. ]20[

5.2.3 Negative PulseNegative pulse tools briefly open and close the valve torelease mud from inside the drillpipe out to the annulus.This produces a decrease in pressure that can be seen atsurface. Line codes are used to represent the digitalinformation in form of pulses. ]20[

Fig.5.3: Position of Mud Pulse Telemetry in Drill String. ]23[


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5.2.4 Continuous WaveThis system uses a slotted disk and creates a frequencymodulation of the carrier wave. The speed oftransmission is between 4000-5000 ft/sec in the drillingfluid.This type of pulsing system requires no majormodification to the rig and is a lower cost systemcompared to hardwire systems. This siren system has ahigher data rate compared to the positive and negativepulsars, and because of this more sensors are possible.The main drawbacks of the mud siren are the slotted diskis prone to plugging by LCM, there is no transmissionwith the pumps off, and the system has a low signal tonoise ratio. This system is used bySchlumberger/Anadrill. ]20[

Mud pulse telemetry is unusable in underbalanced drilling. This is because ofreduction of mud density (a compressible gas) injected to the mud. This causes highsignal attenuation which drastically reduces the ability of the mud to transmit pulseddata. It is necessary to use other methods such as electromagnetic wavespropagation through the formation or weird drill pipe telemetry, than mud pulsetelemetry in this situation. The offering bandwidth in Current mud pulse telemetrytechnology is up to 40 bps (bits per second).The data rate drops with increasingdepth of the wellbore is typically as low as (1.5 - 3.0) bps, at the depth of 35,000 ft -40,000 ft (10668 m - 12192 m).

Communication between surface and downhole is done via changes to drillingparameters, i.e. change of the drill string’s rotation speed or flow rate of mud.Changing in the drilling parameters in order to send information can requireinterruption of the drilling process, which is unfavorable due to the fact that it causesnon-productive time.

5.3 Electromagnetic telemetry (EM Tool):

EM-MWD uses low-frequency electromagnetic waves to transmit downholemeasured data in real time to the surface during conventional and underbalancedhorizontal and directional drilling operations. EM telemetry transmits informationthrough the formation to a surface antenna, where it is received and sent to a dataacquisition system to be decoded and processed. This system generally offers datarates of up to 10 bps. In addition, many of these tools are also capable of receivingdata from the surface in the same way, while mud pulse-based tools rely on changesin the drilling parameters. Operators using EM-MWD are able to drill and survey wellsindependent of rig hydraulics. Bit pressure drop, flow rates, drilling fluid and losses tothe formation are transparent to the technology.


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These capabilities equate to substantial savings in drilling time and total project cost.However, it generally falls short when drilling exceptionally deep wells and the signalcan lose strength rapidly in certain types of formations, becoming undetectable atonly a few thousand feet of depth. Receivers have to be placed over a wide area,and this limits their use offshore. This system is used by Geoservices.

5.4 Wired Drill Pipe:

Wired drill pipe systems are developing by severaloilfield companies. These systems use electricalwires built into every component of the drillstring,which carry electrical signals directly to thesurface. Wired pipe telemetry systems, however,can provide a bandwidth of up to 57,600 bits/secand can transmit data from downhole tools tosurface at high update rates. Real-timetransmission of information is not affected bydepth, formation resistivity, fluid properties or flowrates.


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One of the newest wired pipe networks is The IntelliServ which offering data ratesupwards 1M bit/s and become commercial in 2006. This system has been used andtested by some of oil companies as BP America, Statoil Hydro, INTEQ, andSchlumberger presented three success stories using this system, both onshore andoffshore, at the March, 2008 SPE/IADC Drilling Conference in Orlando, Florida.

5.5 Retrievable tools:

MWD tools may be semi-permanently mounted in a drill collar (only removable atservicing facilities), or they may be self-contained and wireline retrievable.Retrievable tools, sometimes known as Slim Tools, and they can be retrieved andreplaced by using wireline in the drill string. This usually allows the tools to replacemuch faster in case of failure, also in case of stacking of drillstring; it allows the toolto be recovered. Retrievable tools must be much smaller, usually about 2 inches orless in diameter, and their length may be 20 feet or more. The small size isnecessary for the tool to fit through the drillstring; however, it also limits the tool'scapabilities.

For example, slim tools are not capable of sending data at the same rates as collarmounted tools, and they are also more limited in their ability to communicate with andsupply electrical power to other LWD tools. Collar-mounted tools, also known asFat Tools, cannot generally be removed from their drill collar at the well site. If thetool fails, the entire drillstring must be pulled out of the hole to replace it. However,without the need to fit through the drillstring, the tool can be larger and more capable.The ability to retrieve the tool via wireline is often useful. For example, if the drillstringbecomes stuck in the hole, then retrieving the tool via wireline will save a substantialamount of money compared to leaving it in the hole with the stuck portion of thedrillstring. However, there are some limitations on the process.


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5.6 Logging while drilling (LWD)

LWD is a technique of transporting well logging tools into downhole of the well aspart of the BHA. The combination of LWD tools and MWD system transmit partial orcomplete measurement results to the surface via a drilling mud pulser or otherimproved techniques, while LWD tools are still in the borehole, which is called "RealTime Data". Real-time data from LWD services let us make timely, informeddecisions, reducing time and costs. Complete measurement results can bedownloaded from LWD tools after they are pulled out of hole, which is called"Memory Data". LWD data will be collected during drilling operations. Collecting andprocessing data due drilling operations eliminate the requisition of drilling assemblyto insert a wireline logging tool.

LWD technology was developed originally as an enhancement to the earlier MWDtechnology to completely or partially replace wireline logging operation. Developing ofthe technology in the past decades, LWD widely is used for drilling (includinggeosteering), formation evaluation (especially for real time and high angle wells).

By LWD drilling process will be controlled better and be allowed performanceoptimization and minimizing down time. Scope services dramatically improve drillingperformance, opening a new era in data excellence. Increase the rate of penetration,improve wellbore stability and hole quality, and optimize well placement for maximumproduction faster. ]23[


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5.6.1 Available LWD Measurements:

LWD technology was originally developed to partial or complete replace wirelinelogging. Over the years, majority of the measurements have been made available inLWD. Certain new measurements are also development in LWD only. The followingis an incomplete list of available measurement in LWD technology. ]23[

Natural Gamma Ray (GR)

Total Gamma Ray

Spectral Gamma Ray Azimuthal Gamma Ray Gamma ray close to drill bit.

Density and Photoelectric Index Neutron Porosity Borehole Caliper

Ultra sonic azimuthal caliper. Density Caliper

Resistivity (ohm-m)

Attenuation and phase shift resistivity at different transmitter spacing andfrequencies.

Resistivity at the drill bit. Deep directional resistivity

Sonic

Compression Slowness(Δtc) Shear Slowness (Δts)

Borehole Images

Density Borehole Image Resistivity Borehole Image

Formation Tester and Sampler

Formation Pressure Formation Fluid Sample

Nuclear Magnetic Resonance (NMR) Seismic While Drilling (SWD)

Drill bit-SWD VSP-WD (Vertical Seismic Profile While Drilling


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5.7 MWD/LWD Advantages:

The advantages of MWD/LWD can be described in three areas: Directional ControlUsing multiple accelerometers and magnetometers, MWD surveys makemuch more accuracy in location of drill bit in the well.Reduction in survey downtime and reduce of risk in differentially sticking ofthe drill string. Formation EvaluationReal time logging results in quick evaluation of formation data and this resultsto fast, accurate correlation decisions. Information can be gained beforesignificant hole deterioration takes place, prior to significant filtrate invasion,and the hole is logged and information gained before the possible loss of thehole.This real time information can eliminate top hole wireline log runs, and withthe real time pore pressure information can eliminate planned casing string.

Drilling safety and OptimizationThis information provide by MWD allows for make drilling efficiency andimproved bit performance by indicating formation changes. The informationallows for improved pore pressure evaluation, highlighting the safety aspectsof MWD

5.8 MWD/LWD Disadvantages:

Inclinations errors by: Movement of MWD tools Misalignment of MWD collar in the borehole Misalignment of accelerometer Temperature fluctuations

Azimuthally errors:

Wrong positioning of the magnetic parts Problem with LWD power Wrong estimation of collar mass Collar Hot Spots problem

Micro-Resistivity imaging and fluid sampling can’t be done by LWD tools.


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Chapter 6Miscellanies


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Introduction:

The accurate predication of pore pressure in shale has become almost essential tothe drilling of deep wells with higher then normal pore pressure. Shale pressure canbe the major factor affecting the success of drilling operations. Unfortunately, shalepressure can be very difficult to quantify precisely where unusual or abnormalpressure exists. If pressure is not properly evaluated, it can lead to drilling problemssuch as lost circulation, blowouts, hole instability, and excessive costs. Thus drillingcosts and problems can be reduced substantially by the early recognition ofabnormally high pore pressures. In this chapter we try to present the most world wideused for estimation pressure in shale which has capability for an abnormal pressurein formation. Some of these methods are:

Eaton Method

Equivalent depth method

Ratios Method

Vertical and Horizontal Methods

Compaction Concept Method

Power Law Method


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6.1 Eaton Method

The Eaton Method is typically applied to seismic oracoustic velocity data, and resistivity data. Theprocedure is to examine the porosity vs. depth dataand to make a ratio comparison between the valuerecorded and the expected value if the pore pressureswhere hydrostatic, i.e. plotted on the normalcompaction curve.

Application: Interval velocity

d-exponent

Resistivity/Conductivity

Sonic log

Shale density

Density log

Principles:Relationship between the observed parameter & normal

parameter ratio and formation pressure depends on

change in overburden pressure. Eaton in 1972

established the following empirical relationship from real

Data:5.1

n,sh

a,shn,povbovbpore R

R)PP(PP

…………………...6.1 Eaton(1972)

With more experimental data and performing of his studies he published his result in

1975 as following formulas:

2.1

n

an,povbovbpore R

R)PP(PP

……………………..6.2 Resistivity

3

a

nn,povbovbpore t

t)PP(PP

……….……………..6.3 Sonic

2.1

n.c

a.cn,povbovbpore d

d)PP(PP

…………….......…6.4 dc-exponent


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where aR , nR , at , nt , ad and n.cd are Resistivity (ohm) ,Sonic transit time

(μsec/ft or (μsec /m) and dc-exponents for normal and actual case.

“This method is empirically derived. It assumes that a normal trend can be defined

and that the pore pressure at any point can be related to the ratio between actual and

normal indicator value.

6.2 Equivalent Method

The method of equivalent depth is based onthe assumption that the same shale withequal physical properties at different depthswill have equal effective stress.

Applications:Interval velocities exponent, shale density,

Resistivity, Conductivity, Sonic, Density

loges and any direct or indirect

measurements of clay porosity.

Principle:Every point A in an under compacted clay isassociated with a normally compacted pointB The compaction at point A is identical tothat at point B (Fig. 6.2) The depth of pointB, Z B is called the equivalent depth, orsome times the isolation depth. The fluidcontained within the pores of clay A hasbeen subjected to all geostic loads in thecourse of burial from Z B to Z A .

We know that:

poreovb PP …………………..……………….….6.2.1

B,poreB,ovbB PP ……………….………….. ……. 6.2.2

AB With knowing the overburden pressure at A ( A,ovbP ), the pore pressure at A ( A,poreP )can be calculated.


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BA,ovbA,pore PP …………………………….. 6.2.3

Then by eliminating A and B :

B,ovbA,ovbB,poreA,pore PPPP ……………..….6.2.4

It is necessary to correct all parameter values for temperature, especially when theresistivity data are used as a geophysical property to identify equivalent depths.

Example:

ZA=3500 m, ZB=2500m,n,pG = 1, 06

n,ovbG = 2, 20 at depth B & 2, 26 at depth A

2B

B,pore cmkg26506,,1

10350006,1

10ZP

2B

B,ovb cmkg55020,2

10ZP

2A

A,ovb cmkg79126,2

10ZP

B,ovbA,ovbB,poreA,pore PPPP 2A,pore cmkg506)550791(265P

The formula to be used at the well site, when the overburden gradient is known, is:

)G(ZZG B,EqB,ovb

A

BA,ovbA,Eq ………….……..6.2.5

A,Eq : Equilibrium density at A

B,Eq : Equilibrium density at B

Z A : Equivalent depth

Z B : Depth of the under compacted Clay

B,ovbG : Overburden gradient at A

A,ovbG : Overburden gradient at B


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6.2.1 Calculation of Overburden Gradient:Overburden pressure may be calculated from eq. below:

10ZP bovb …………………………………………………..……..6.2.6

Where:

P ovb : Overburden Pressure [kg.f/cm²]

b : Bulk density [g/cm³]

Z : Depth [m]

PS! 1 Kg force = 14.2233 Psi

= 0.980665 Bar

=0.0980665 MPa

“If data for calculation of overburden gradient are not available, an average

overburden gradient may be used. The value normally taken is 2.31 (), which

corresponds to an average established for the Gulf Coast. This value produces only

a small error in the case of onshore wells.

PS: it should NOT be used offshore if all possible, particularly where the water is

deep and the well is shallow.” ]22[

When the normal pressure gradient is not known an average value of 1.05 may besubstituted for it. Pn =1.05Briefly formula for constant gradients ( B,Eq =1.05, A,ovbG = B,ovbG =2.31)

)G(ZZG B,EqB,ovb

A

BA,ovbA,Eq

A,Eq =2.31-A

B

ZZ (2.31-1.05) )

ZZ(26.131.2

A

BA,Eq ………….6.2.7


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6.3 The Ratio Method

Applications: d-exponent

Shale density

Sonic log

Resistivity

Density log

Principle:The ratios method is based on this idea that the

difference between the observed and normal values

of parameters is proportional to the increase in

pressure. Thus the ratio of the observed (for

example, dco) to the normal (dcn) value is

proportional to the formation pressure (Fig 6.3).

To apply the ratios method to dco/dcn, use the formula below:

o,c

n,c.hydF d

dGPGP …………………………………6.3.1

FGP : Formation pressure gradient (mud density equivalent)

.hydGP : Normal (hydrostatic) pressure gradient (mud density equivalent)

The ratio method is unsuitable for most of shale formations. The main limitation here

is that draw isodensity lines for most regions, a given set of isodensity lines is only

valid for the specific abnormal pressure condition of the well on which they were

computed.


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6.3.1 Isodensity Concept:

The equilibrium density is obtained using the

following formula:

o

nn,eqleql dc

dc ………………….… 6.3.2

n,eql : Normal equilibrium density

o,eql : Observed equilibrium density

ndc : Normal d-exponent

odc : Observed d-exponent

A set of isodensity lines can be drawn using the

following formula (Fig.6.4) so that the equilibrium

densities can be read off directly.

eql

n,eqlno dcdc

………………………6.6.3

6.3.2 Establishing isodensity line (Fig. 6.5) take a point A located on the normal

compaction trend XY

Calculate the value of dc which would be

observed at point A for a given equilibrium

density.

Using this value (B) draw a straight line

X’Y’ parallel to XY. This represents the

gradient of the selected equilibrium

density.

for the given density of ( A.eql ), calculatethe parameter values, dc,o that would beobserved at depth A, using the followingformula:

A.eql

.EMWcnco dd

…………………… 6.6.4


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Example:

180dcn , 05.1n,eql

eqlo

50.180.1dc

To draw the isodensity line 20.1eql

58.120.150.180.1dco

The ratio method is easy and very widely used. However, because it is empirical,

the results obtained are not always satisfactory. Adjustment of the calculations of

the calculations on the basis of measurements (RFT.test) can appreciably

improve the results of the method with the introduction of a correction

coefficient(c):

So that:o

nn,eqleql dc

dcc ……………..…..6.6.5

Example:

Calculated 25.1eql

35.1RFT eql

08.125.135.1c

The correction coefficient remains valid as long as the cause of the abnormal

pressure condition remains the same.

o,c

n,c.hydF d

dGPcGP ………………………..……..6.6.6 ]22[


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6.4 Vertical and Horizontal Models Method

One of the new methods for pressuremeasurement in shale is estimation porepressure by Vertical or Horizontal methods.

Applications:Interval velocities-exponent, Shale density,

Resistivity/Conductivity and acoustic travel

time.

Principle:

For vertical assumption:

DD

)PP(PP en,peovbpore ……………...…6.4.1

Where:

P e : overburden pressure where the verticalline crosses the compaction line.

De: depth where the vertical line crosses thecompaction line.

For Horizontal assumption:

x

n,povbovbpore MN)PP(PP

……………....6.4.2

Where:

(MN ) : Ratio of measured value (i.e. velocity, resistivity or acoustic travel time) to

the expected value at normal trend line at the same depth.

x : an empirical exponent. The horizontal derived pressureIn some case as Fig.6.7 assuming value of x is 3. (x=3)


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Horizontal method that correlateMN directly to pore pressure without an overburden

term(e.g. Hottmann and Johnson) require local calibration to account for changes inwater depth and should be used with direction. ]24[

More realistic well data fitting on this method has been done in appendix C.


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6.5 Pore Pressure in Overconsolidated Shale

In some geological basin man can not establish normal compaction trend line,special in overconsolidated Shale basin. But predication of pore pressure inoverconsolidated shale has been developed by using sonic loges and the methodgave a certain results for establishing pore pressure in the over consolidated Albertabasin in Canada.

Applications: Terzaghi stress relationship : PoreT P

Eaton general Eq. :x

norm

obsn,povbovbpore A

A)PP(PP

Where:

obsA : Observed attribute

normA : Normal attributeX : Empirical fitting constant

Bowers normal compaction curve define as:

BnormA5000V ……………………………...6.5.1

Where:

V : Sonic velocity [ft/sec]norm : Effective stress

A & B: Curve fitting constant for normal compacted shale

Principle:

“ Max ”can be calculated from rearranging of Eq.6.5.1 as below:

B1

maxMax A

5000

…………………………..….6.5.2

Where:Max : Max effective stress corresponds to Max

Max : Sonic velocity which is the onset point of the unloading [ft/sec]

BAovbpore ])5000V[(PP ……………….….…6.5.3

And A´ and B´ are calculated from:

)BU(

MaxBMaxAA

……………………………6.5.4


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UBB ..................................................................6.5.5

Where:

Max : Max. Effective stress [SG]U : Unloading curve parameter (U= 3.13, For Golf Cost, Bower 1995)

The result of predication of pore pressure by overconsolidated method illustrated onFig.6.8.Further calculation has been done in Appendix D.


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6.6 Compaction Concept Method

Application:

Interval velocities-exponent, Shale density, Resistivity/Conductivity andacoustic travel time

Terzaghi stress relationship Wyllie’s time Eq. for porosity

Normally formation pressure in shale can be calculated from Eq.1.2“ )Kexp( vi ” which is relationship between porosity and vertical stressas follow:

)Kexp( vin ………………….……….6.6.1

Where:

n : Shale porosity in normal formation pressure

i : Porosity of shale at the surfaceK : Porosity decline constant

v : Vertical stressBy using of Terzaghi stress relationship ( porevovb P ) in Eq.6.6.1 we cancalculate porosity in abnormally formation pressure as follow:

)]P(Kexp[ porevia ……………………..…6.6.2

Where:

ovb : overburden stress

poreP : Pore pressure

Then by using Wyllie’s time Eq. for porosity and rearrange it for calculation traveltime in normal and abnormal formation pressure as follow:

mfl

m

tttt …………………Wyllie’s Eq. for porosity and simplified and reduced

to:

bmt ……………………..………………..6.6.3


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Where mfl ttm and mtb Thus travel time in normal compaction will be:

bmt nn ……………………………………...6.6.4

And under abnormal pressure conditions:

bmt aa ……………………………………6.6.5

Substituting Eq. 6.6.1 to Eq.6.6.4 and Eq.6.6.5 leads to:

)Kexp(mt vin ………………………..…….6.6.6

)]P(Kexp[mt poreovbia ………..………..6.6.7

By subtracting Eq.6.6.6 & Eq. 6.6.7 and assuming that b is constant the results willbe as follow:

)]Kexp()P(K[exp(mtt vporeovbina ……………6.6.8

Taking logarithm in both sides and rearrangement for pore pressure gives:

)Kexp()tt(mlnK1P vnaiovbpore ……….………...6.6.9

Procedure: Plot Depth-transit time ( t ) Determine i ,use multi-regression analysis Calculate sh Plot ( t - sh ) Determine slop m from Plot ( t - sh ) Determine the normal trend line From normal trend line, obtain nt and at Calculate ( at - nt ) Calculate shale pressure.


NTNU | Atumn2009 89

Fig. 6.1 shows the result of pore pressure estimation by using the CompactionConcept method. ]26[

6.7 Power Law Relationship Method

Application:

Interval velocities-exponent, Shale density, Resistivity/Conductivity andacoustic travel time

Terzaghi stress relationship Wyllie’s time Eq. for porosity

Shae pressure can be determined from power low by:

Dna

pre ba

ttlog

blogDP ………….…6.7.1

Where:

P pore : Shale pressure [psi]D : Depth of insert [ft]

at : Abnormal transit time [ftsec ]

nt : Normal transit time [ftsec ]

a : The interceptb : Slop

=D

v : Vertical stress gradient [ ]ft

psi

Procedure:

Plot Depth-transit time ( t ) Determine the normal trend line From normal trend line, obtain nt and at Calculate ( at - nt ) Calculate shale pressure.


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Over All Conclusions:

Porosity based pore predication techniques work best where a “normalcompaction curve “ can be reliably developed, where the lithology ismoderately constant , and where the overpressure is due to disequilibriumcompaction.

Lithological variability and shallow overpressure create difficulty in defining theappropriate normal compaction trend for pore pressure estimation.

Wireline log analysis is still one of the major methods employed to estimatepore pressure. It is used to create models of pressure in offset wells during theplanning of drilling programs. Many methods of pore pressure estimation, suchas that from resistivity, sonic and density logs, require many assumptionsabout the rock properties, and d so, unless copious amount of calibration datahas been produced, that accurate estimation of porosity from wireline logs isdifficult. In this project it has been tried to show some of the benefits methodsto estimate and calculating of Pore pressure in shale based on the availablewell data!

Most of above challenges lead to an underestimate of the pore pressure,which it can lead to drilling surprise.

Recommendation and further work

Taking direct pressure measurement in all permeable formation –nothingadequately replaces the benefit of knowing the true pore pressure.

Employments of multiple techniques in pore pressure predication to helpunderstand the uncertainty in each of the method used. For example,employing basin modeling, seismic and wireline–based predication techniquesprovide complementary results and valuable insights into the realistic range ofuncertainty in predication.

It seems that its time to work more on Direct Pressure measurement in shaleand for that part of study the following points may recommend:

1. Study on techniques to measure pore pressure in shale directly.2. Investigate near wellbore environment3. Quick methods to directly measurement of pore pressure in shale in

open hole or closed hole.4. Completion design and cost.5. Short term test design and cost.6. Recommended well and test design


NTNU | Atumn2009 91


NTNU | Atumn2009 92

References:

1. Richard.E.Swarbrick-Chalenges of Porosity-Based Pore PressurePredication.

2. B.E Law, G.F.Ulmishek, V.I.Slavin, Abnormal Pressures inHydrocarbon Environments

3. Paul brown, Richard E. Swarbrick, Andrew C. Aplin and Niall Hoey,Porosity: an Essential tool for the estimation of pore fluid pressurein Shales.

4. P. Magarini, C. Lanzetta, A. Galletta, Eni. Over pressure evaluationManual. Page 250-255.

5. Rabia. Hussain ,Well Engineering & Construction6. Schlumberger, RFT ,ESSENTIAL OF PRESSURE TEST

INTERPRETATION ,Page 11-267. Stephen O'Connor1, Richard E. Swarbrick, Phillip Clegg, and David T.

Scott, Pore Pressure Profiles in Deep Water Environments: CaseStudies from Around the World

8. W.H FERTL Abnormal Formation Pressure

9. www.netl.doe.gov/.../ANSWell/MDTool.html10. Statoil-Hydro, Direct Pressure measurement in shale (MESPOSH)11. http://www.halliburton.com/ps/Default.aspx?navid=159&pageid=39612. Vaughan P.R.(1969), A note on sealing piozometers in boreholes

Geotechnique

13. Morten H. Detholff, Halliburton, and Steen Agerline Petersen,NorskHydro, Seismic-While-Drilling Operation and Applications.

14.R.J. Meehan, Schlumberger Cambridge Research; L. Nutt,’Schlumberger Wireline and Testing; N. Dutta, BP; and J. Menzies,Lasmo IDAC/SPE, Drill Bit Seismic: A Drilling Optimization Tool

15.A Review of Seismic-While Drilling (SWD) Techniques: A Journeyfrom 1986 to 2005 A. Anchliya, SPE Indian School and Mines.

16.B.Cornish , SPE , and R .Deady , SPE, Halliburton Energy Services,Next Generation Multisensour Seismic-While-Drilling Technology

17. Ray Pratt, Peter K. Keller & SolveigLysen, HPHT Sonic ExplorationWellPore WellPore Pressure Prediction and Monitoring: UtilisingVSPLook-Ahead, MWD Resistivity and MWD Sonic HPHT Sonic, A case studyfrom the Central Grabenof the North Sea

18.Dr.Tanguy and W.A. Zoeller, SPE, Application of measurement whiledrilling

www.netl.doe.gov/

http://www.halliburton.com/ps/Default.aspx


NTNU | Atumn2009 93

19.Zarool Hassan bin Tajul, Petronas Carigali sdn.Bhd. SPE: The Benefitsof Logging while Drilling (LWD) for formation Evaluation in theDulang west Filed.

20.Rev.A, Baker Haugh, Advance Wireline & MWD Procedure. Page:1-1to 3-10

21.Ed.Tollefsen, SPE, Amandaweber, SPE, and Aron Corporation, and LisaGrant, SPE, Shell, Logging While Drilling Messurements: FromCorrelation to Evaluation.

22.J.P MOUCHET AND A. MITCHELL ,Abnormal pressure while drillingPage 140-167

23.Paul Radzinski, Weatherford International Ltd. LWD/MWD combo forextreme environments.

24. Martin Traugott, Amoco E&P Technology, Houston, Texas,PorePressure and Fracture Pressure Determinations in Deepwater

25. R.Nygaard, M.Karimi, G.Hareland and M.Tahmeen and H.MunroPore-Pressure Predication in Overconsolidated Shales

26. A.Draou,Sonatrach,PED,Algeria and S.O.Osisanya,SPE,The universityof Oklahoma, New Methods for Formation Pressure and FractureGradients from Well Logs.

27. G.V. Chilingar, V.A.serebryako, J.O.Robertson, Jr. Origin andPrediction of Abnormal Formation Pressures


NTNU | Atumn2009 94

Well data and fitting to pressure calculationmethods:

APPENDIX A:

1. Eaton Method:

Well Name: 6608 10-E-3 HFelt: Norne

TABLE 1: Well data

DEPTH TVD DT GR NPHI RHOB2440.625 2363.7244 117.4046 80.2465 0.3319 2.3022440.75 2363.8445 117.5041 79.1689 0.3327 2.31672440.875 2363.9646 117.6487 81.9878 0.3313 2.3353

2441 2364.0845 117.7898 83.8123 0.3223 2.332441.125 2364.2046 117.8284 83.1971 0.3323 2.332441.25 2364.3247 117.7269 90.1494 0.339 2.332441.375 2364.4448 117.5482 95.7786 0.3503 2.332441.5 2364.5649 117.3473 99.1985 0.3519 2.33

2441.625 2364.6851 117.1681 98.577 0.3394 2.32842441.75 2364.8052 117.0302 85.5132 0.3421 2.32022441.875 2364.925 116.8764 80.7847 0.3444 2.32

2442 2365.0452 116.6941 79.9678 0.3494 2.322442.125 2365.1653 116.5111 81.0235 0.3241 2.32442442.25 2365.2854 116.3445 80.7457 0.289 2.32872442.375 2365.4055 116.2053 76.62 0.2913 2.32462442.5 2365.5256 116.1282 74.5032 0.3108 2.3205

2442.625 2365.6455 116.14 84.6392 0.2964 2.31572442.75 2365.7656 116.2257 89.4405 0.2832 2.31182442.875 2365.8857 116.3676 89.8491 0.2833 2.3078

2443 2366.0059 116.5407 86.9438 0.2979 2.30682443.125 2366.126 116.714 76.215 0.317 2.3192443.25 2366.2461 116.8771 83.6836 0.3184 2.30092443.375 2366.3662 117.1356 84.6597 0.3131 2.31572443.5 2366.4861 117.5365 83.1574 0.3084 2.3237


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2443.625 2366.6062 118.0558 82.2568 0.3056 2.31792443.75 2366.7263 118.6244 83.4279 0.3052 2.312443.875 2366.8464 119.147 84.0728 0.322 2.31

2444 2366.9666 119.5855 81.2831 0.3183 2.32192444.125 2367.0867 120.0449 81.1417 0.3238 2.34752444.25 2367.2065 120.5087 81.5558 0.3274 2.3522444.375 2367.3267 120.8572 80.8789 0.323 2.32852444.5 2367.4468 120.8677 79.6757 0.3184 2.3109

2444.625 2367.5669 120.185 80.4347 0.3132 2.30852444.75 2367.687 119.131 80.049 0.3194 2.3222444.875 2367.8071 118.0887 77.4081 0.3232 2.3232

2445 2367.9272 117.2851 77.4045 0.3219 2.31762445.125 2368.0471 116.8237 83.1754 0.3179 2.31912445.25 2368.1672 116.653 84.059 0.3136 2.31992445.375 2368.2874 116.5115 76.9195 0.3056 2.322445.5 2368.4075 116.3469 78.3222 0.304 2.3265

2445.625 2368.5276 116.2236 85.6607 0.3029 2.33512445.75 2368.6477 116.1818 90.1324 0.3006 2.34032445.875 2368.7676 116.219 81.9887 0.3017 2.338

2446 2368.8877 116.2871 87.889 0.3236 2.33892446.125 2369.0078 116.3207 83.9365 0.3374 2.34112446.25 2369.1279 116.3203 80.1609 0.3278 2.3412446.375 2369.248 116.3057 79.4951 0.3132 2.33572446.5 2369.3682 116.3113 81.2473 0.3103 2.3238

2446.625 2369.488 116.3901 81.4746 0.3054 2.30662446.75 2369.6082 116.5629 81.4743 0.3001 2.28232446.875 2369.7283 116.7513 82.2029 0.3001 2.3212

2447 2369.8484 116.898 82.7503 0.2991 2.33662447.125 2369.9685 116.9703 82.0445 0.2999 2.3162447.25 2370.0886 116.9717 79.8115 0.3114 2.30832447.375 2370.2087 117.0152 82.2263 0.3245 2.3232447.5 2370.3286 117.2242 82.5584 0.3042 2.3236

2447.625 2370.4487 117.5478 77.2398 0.2869 2.32672447.75 2370.5688 117.881 77.0379 0.2879 2.33842447.875 2370.689 118.1049 84.7637 0.2994 2.3504

2448 2370.8091 118.114 82.245 0.2807 2.3332448.125 2370.9292 117.8998 82.2296 0.2884 2.322448.25 2371.0491 117.6524 81.6784 0.3063 2.31262448.375 2371.1692 117.4475 80.9829 0.3212 2.32132448.5 2371.2893 117.3019 80.7431 0.3262 2.3391


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2448.625 2371.4094 117.1866 80.9523 0.3197 2.3482448.75 2371.5295 117.0413 77.6801 0.3042 2.33082448.875 2371.6497 116.8531 81.0555 0.3076 2.3224

2449 2371.7698 116.6733 78.7203 0.3008 2.322449.125 2371.8896 116.5405 78.509 0.2922 2.31632449.25 2372.0098 116.4731 83.0292 0.2941 2.31372449.375 2372.1299 116.4606 82.6097 0.3128 2.32892449.5 2372.25 116.4402 84.6979 0.309 2.3232

2449.625 2372.3701 116.387 78.7641 0.3179 2.31812449.75 2372.4902 116.3515 79.4627 0.3252 2.32552449.875 2372.6101 116.3938 83.9224 0.3274 2.3354

2450 2372.7302 116.568 83.4074 0.3239 2.33352450.125 2372.8503 116.9096 79.7553 0.303 2.33032450.25 2372.9705 117.3016 80.6818 0.3195 2.34212450.375 2373.0906 117.6277 84.6196 0.3197 2.33732450.5 2373.2107 117.8483 84.8524 0.3129 2.3258

2450.625 2373.3308 117.9491 81.3144 0.3065 2.31842450.75 2373.4507 117.9364 81.5475 0.2996 2.31972450.875 2373.5708 117.811 79.2869 0.3199 2.3123

2451 2373.6909 117.6017 83.5463 0.3157 2.31442451.125 2373.811 117.3436 83.4971 0.3209 2.3222451.25 2373.9312 117.0784 81.0548 0.3257 2.3222451.375 2374.0513 116.8508 81.074 0.3143 2.30912451.5 2374.1711 116.7066 83.0088 0.298 2.31

2451.625 2374.2913 116.6531 83.9225 0.3133 2.31392451.75 2374.4114 116.6328 83.4275 0.2894 2.3182451.875 2374.5315 116.6209 83.1111 0.2799 2.3154

2452 2374.6516 116.5965 83.3055 0.2956 2.31192452.125 2374.7717 116.5467 82.7236 0.3029 2.32192452.25 2374.8918 116.4999 76.5878 0.3073 2.33422452.375 2375.0117 116.514 84.1983 0.3037 2.31782452.5 2375.1318 116.59 87.4743 0.3035 2.3131

2452.625 2375.252 116.7125 85.6945 0.3042 2.31742452.75 2375.3721 116.8548 82.3477 0.3066 2.32112452.875 2375.4922 116.9818 79.3766 0.3255 2.3269

2453 2375.6123 117.0626 77.4238 0.3343 2.32942453.125 2375.7322 117.113 85.4496 0.3351 2.33


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TABLE 2:Calculated Eaton method:GPn= 1.05 x=3

3

a

nn,povbovbpore t

t)PP(PP

TVD DT N Dt RHOB Gob Gob-(Gob-GPn) N Dt/Dt GPpore Ppore[kg/Cm2]2363.7244 117.4046 118 2.302 2.30 1.05 1.01 1.079 25502363.8445 117.5041 118 2.3167 2.31 1.05 1.01 1.076 25432363.9646 117.6487 118 2.3353 2.32 1.05 1.01 1.071 25332364.0845 117.7898 118 2.33 2.33 1.05 1.01 1.067 25232364.2046 117.8284 118 2.33 2.33 1.05 1.01 1.066 25202364.3247 117.7269 118 2.33 2.33 1.05 1.01 1.069 25262364.4448 117.5482 118 2.33 2.33 1.05 1.01 1.073 25382364.5649 117.3473 118 2.33 2.33 1.05 1.01 1.078 25502364.6851 117.1681 118 2.3284 2.33 1.05 1.01 1.083 25612364.8052 117.0302 118 2.3202 2.32 1.05 1.01 1.087 25702364.925 116.8764 118 2.32 2.32 1.05 1.01 1.091 2580

2365.0452 116.6941 118 2.32 2.32 1.05 1.01 1.096 25912365.1653 116.5111 118 2.3244 2.32 1.05 1.02 1.100 26032365.2854 116.3445 118 2.3287 2.33 1.05 1.02 1.105 26142365.4055 116.2053 118 2.3246 2.33 1.05 1.02 1.109 26222365.5256 116.1282 118 2.3205 2.32 1.05 1.02 1.111 26272365.6455 116.14 118 2.3157 2.32 1.05 1.02 1.110 26262365.7656 116.2257 118 2.3118 2.32 1.05 1.02 1.107 26192365.8857 116.3676 118 2.3078 2.31 1.05 1.02 1.103 26092366.0059 116.5407 118 2.3068 2.31 1.05 1.01 1.098 25972366.126 116.714 118 2.319 2.31 1.05 1.01 1.093 2585

2366.2461 116.8771 118 2.3009 2.31 1.05 1.01 1.088 25742366.3662 117.1356 118 2.3157 2.31 1.05 1.01 1.080 25562366.4861 117.5365 118 2.3237 2.32 1.05 1.01 1.069 25302366.6062 118.0558 118 2.3179 2.32 1.05 1.00 1.055 24962366.7263 118.6244 118 2.31 2.31 1.05 1.00 1.039 24602366.8464 119.147 118 2.31 2.31 1.05 0.99 1.026 24272366.9666 119.5855 118 2.3219 2.32 1.05 0.99 1.014 24002367.0867 120.0449 118 2.3475 2.33 1.05 0.98 1.002 23722367.2065 120.5087 118 2.352 2.34 1.05 0.98 0.990 23442367.3267 120.8572 118 2.3285 2.34 1.05 0.98 0.982 23242367.4468 120.8677 118 2.3109 2.32 1.05 0.98 0.981 23232367.5669 120.185 118 2.3085 2.32 1.05 0.98 0.998 23622367.687 119.131 118 2.322 2.32 1.05 0.99 1.024 2425

2367.8071 118.0887 118 2.3232 2.32 1.05 1.00 1.051 24892367.9272 117.2851 118 2.3176 2.32 1.05 1.01 1.073 25402368.0471 116.8237 118 2.3191 2.32 1.05 1.01 1.085 25702368.1672 116.653 118 2.3199 2.32 1.05 1.01 1.090 25812368.2874 116.5115 118 2.32 2.32 1.05 1.01 1.093 25902368.4075 116.3469 118 2.3265 2.32 1.05 1.01 1.098 26002368.5276 116.2236 118 2.3351 2.33 1.05 1.02 1.101 26082368.6477 116.1818 118 2.3403 2.33 1.05 1.02 1.102 26102368.7676 116.219 118 2.338 2.34 1.05 1.02 1.101 2607


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2368.8877 116.2871 118 2.3389 2.34 1.05 1.02 1.098 26022369.0078 116.3207 118 2.3411 2.34 1.05 1.01 1.097 25992369.1279 116.3203 118 2.341 2.34 1.05 1.01 1.097 25992369.248 116.3057 118 2.3357 2.34 1.05 1.01 1.097 2599

2369.3682 116.3113 118 2.3238 2.33 1.05 1.01 1.097 25982369.488 116.3901 118 2.3066 2.32 1.05 1.01 1.094 2593

2369.6082 116.5629 118 2.2823 2.30 1.05 1.01 1.089 25812369.7283 116.7513 118 2.3212 2.31 1.05 1.01 1.084 25682369.8484 116.898 118 2.3366 2.32 1.05 1.01 1.079 25572369.9685 116.9703 118 2.316 2.32 1.05 1.01 1.077 25522370.0886 116.9717 118 2.3083 2.31 1.05 1.01 1.077 25522370.2087 117.0152 118 2.323 2.32 1.05 1.01 1.075 25482370.3286 117.2242 118 2.3236 2.32 1.05 1.01 1.069 25342370.4487 117.5478 118 2.3267 2.32 1.05 1.00 1.060 25132370.5688 117.881 118 2.3384 2.33 1.05 1.00 1.051 24912370.689 118.1049 118 2.3504 2.34 1.05 1.00 1.045 2476

2370.8091 118.114 118 2.333 2.34 1.05 1.00 1.044 24752370.9292 117.8998 118 2.32 2.33 1.05 1.00 1.050 24882371.0491 117.6524 118 2.3126 2.32 1.05 1.00 1.056 25042371.1692 117.4475 118 2.3213 2.32 1.05 1.00 1.061 25162371.2893 117.3019 118 2.3391 2.33 1.05 1.00 1.065 25252371.4094 117.1866 118 2.348 2.34 1.05 1.01 1.068 25322371.5295 117.0413 118 2.3308 2.33 1.05 1.01 1.072 25412371.6497 116.8531 118 2.3224 2.33 1.05 1.01 1.076 2553


NTNU | Atumn2009 99

Results & Charts:

Well: N6608 10-E-3 HFelt: NORNE

Chart 1: Sonic travel Time vs. Depth

Fig.A1 : Variation of Sonic travel Time vs. Depth


NTNU | Atumn2009 100

Chart 2: Pressure-Depth based on Sonic log (Eaton-Method)

2000

2100

2200

2300

2400

2500

2600

2700

2800

2900

3000

1500 2500 3500 4500 5500

Dep

th [m

]

Pressure

Pressure-Depth (sonic log-Eaton Method)

Pressure-Depth (soniclog-Eaton Method)

Fig.A2 : Pore pressure predication using Eaton sonic log method.



TABLE 3:Well Name: 34 10-8Felt: Gulfaks

Depth DT N DT RHOB: Depth RT: N RT1800.0839 110.52 128.79 2.5106 1800.0839 1.8132 26.371800.2363 107.68 128.78 2.5309 1800.2363 2.092 26.361800.3885 107.23 128.77 2.4833 1800.3885 2.1565 26.351800.5409 109.88 128.76 2.4139 1800.5409 2.2573 26.331800.6931 113.79 128.75 2.3879 1800.6931 2.1659 26.321800.8455 116.84 128.75 2.3895 1800.8455 1.8692 26.311800.9977 118.83 128.74 2.3814 1800.9977 1.4892 26.29

1801.15 119.60 128.73 2.3836 1801.15 1.3124 26.281801.3024 119.45 128.72 2.3865 1801.3024 1.5854 26.271801.4546 118.32 128.71 2.4333 1801.4546 1.5401 26.251801.6069 114.97 128.71 2.5356 1801.6069 1.4591 26.241801.7592 109.33 128.70 2.6265 1801.7592 1.4346 26.231801.9116 105.79 128.69 2.5825 1801.9116 1.6134 26.211802.0638 107.20 128.68 2.4751 1802.0638 1.5853 26.201802.2162 111.37 128.67 2.3916 1802.2162 1.5338 26.191802.3684 116.65 128.67 2.3723 1802.3684 1.573 26.171802.5208 120.50 128.66 2.377 1802.5208 1.5952 26.161802.673 121.71 128.65 2.3686 1802.673 1.6042 26.15

1802.8254 122.07 128.64 2.3544 1802.8254 1.5701 26.131802.9777 122.30 128.63 2.3432 1802.9777 1.6449 26.121803.1299 122.42 128.63 2.3456 1803.1299 1.9372 26.111803.2822 122.43 128.62 2.3554 1803.2822 2.2573 26.091803.4344 122.34 128.61 2.3607 1803.4344 2.2764 26.081803.5869 122.19 128.60 2.3677 1803.5869 2.107 26.071803.7391 122.04 128.59 2.3776 1803.7391 1.7641 26.061803.8915 121.78 128.59 2.3821 1803.8915 1.5617 26.041804.0437 120.87 128.58 2.3862 1804.0437 1.5339 26.031804.196 118.62 128.57 2.3935 1804.196 1.5641 26.02

1804.3483 113.85 128.56 2.4602 1804.3483 1.6615 26.001804.5007 106.83 128.55 2.6193 1804.5007 2.1972 25.991804.653 102.25 128.55 2.7918 1804.653 3.0196 25.98

1804.8052 101.65 128.54 2.7689 1804.8052 3.2613 25.961804.9575 105.01 128.53 2.5854 1804.9575 3.0526 25.951805.1097 112.12 128.52 2.4286 1805.1097 2.4979 25.941805.2622 117.21 128.51 2.3745 1805.2622 1.8115 25.921805.4144 119.15 128.51 2.3748 1805.4144 1.6181 25.911805.5668 117.77 128.50 2.3987 1805.5668 1.6257 25.901805.719 112.33 128.49 2.454 1805.719 1.6628 25.88

1805.8713 104.83 128.48 2.5869 1805.8713 1.68 25.871806.0237 96.26 128.47 2.7639 1806.0237 1.6976 25.861806.176 91.44 128.47 2.7885 1806.176 1.6929 25.84



1806.3282 91.31 128.46 2.64 1806.3282 1.6663 25.831806.4806 94.52 128.45 2.4796 1806.4806 1.6978 25.821806.6329 100.90 128.44 2.4026 1806.6329 1.8387 25.801806.7852 107.15 128.43 2.3897 1806.7852 1.9774 25.791806.9375 112.59 128.43 2.4068 1806.9375 1.9002 25.781807.0897 115.87 128.42 2.4046 1807.0897 1.9037 25.761807.2422 117.08 128.41 2.3811 1807.2422 1.7412 25.751807.3944 117.81 128.40 2.3646 1807.3944 1.4506 25.741807.5468 118.06 128.39 2.369 1807.5468 1.5931 25.721807.699 118.05 128.39 2.3872 1807.699 1.8348 25.71

1807.8514 117.84 128.38 2.4086 1807.8514 2.2904 25.701808.0037 117.61 128.37 2.4302 1808.0037 2.4362 25.681808.156 117.37 128.36 2.4389 1808.156 2.3071 25.67

1808.3082 117.09 128.35 2.4293 1808.3082 2.0065 25.661808.4607 116.92 128.35 2.4039 1808.4607 1.6708 25.641808.6129 116.99 128.34 2.393 1808.6129 1.6102 25.631808.7651 116.95 128.33 2.4101 1808.7651 1.6707 25.621808.9175 116.07 128.32 2.4432 1808.9175 1.7011 25.611809.0698 113.28 128.31 2.5408 1809.0698 1.7224 25.591809.2222 107.96 128.31 2.6827 1809.2222 1.6438 25.581809.3744 102.82 128.30 2.753 1809.3744 1.5777 25.571809.5267 101.60 128.29 2.6391 1809.5267 1.5785 25.551809.6791 103.90 128.28 2.4942 1809.6791 1.6674 25.541809.8314 108.44 128.27 2.3982 1809.8314 1.7438 25.531809.9836 113.55 128.27 2.3584 1809.9836 1.6038 25.511810.136 117.28 128.26 2.3353 1810.136 1.5887 25.50

1810.2883 119.88 128.25 2.3302 1810.2883 1.6292 25.491810.4406 121.65 128.24 2.3217 1810.4406 1.6515 25.471810.5929 122.78 128.23 2.3272 1810.5929 1.6074 25.461810.7451 123.49 128.23 2.3468 1810.7451 1.5901 25.451810.8975 124.02 128.22 2.3637 1810.8975 1.5852 25.431811.0497 124.59 128.21 2.3707 1811.0497 1.5626 25.421811.202 125.15 128.20 2.3511 1811.202 1.5357 25.41

1811.3542 125.59 128.19 2.3385 1811.3542 1.6244 25.391811.5066 125.67 128.19 2.3404 1811.5066 1.9203 25.381811.6588 125.30 128.18 2.3431 1811.6588 2.1285 25.371811.8113 124.90 128.17 2.3457 1811.8113 2.1652 25.351811.9635 124.69 128.16 2.3451 1811.9635 2.1913 25.341812.1158 124.56 128.15 2.3539 1812.1158 1.9988 25.331812.2681 124.44 128.15 2.375 1812.2681 1.7854 25.311812.4203 124.29 128.14 2.3788 1812.4203 1.6089 25.301812.5726 123.87 128.13 2.3848 1812.5726 1.629 25.291812.7249 122.54 128.12 2.3853 1812.7249 1.8914 25.271812.8772 119.83 128.11 2.397 1812.8772 1.6733 25.261813.0294 115.96 128.11 2.413 1813.0294 1.6437 25.251813.1818 111.45 128.10 2.4336 1813.1818 1.6511 25.231813.334 109.06 128.09 2.4291 1813.334 1.6507 25.22

1813.4865 109.79 128.08 2.4126 1813.4865 1.6618 25.21



1813.6387 112.17 128.07 2.3828 1813.6387 1.7027 25.191813.791 115.80 128.07 2.3873 1813.791 1.7375 25.18

1813.9432 118.78 128.06 2.3874 1813.9432 1.745 25.171814.0956 120.69 128.05 2.3791 1814.0956 1.767 25.161814.2478 121.96 128.04 2.3653 1814.2478 1.7653 25.14

1814.4 122.52 128.03 2.3613 1814.4 1.7065 25.131814.5524 122.68 128.03 2.3619 1814.5524 1.6876 25.121814.7046 122.40 128.02 2.3595 1814.7046 2.0032 25.101814.8569 122.04 128.01 2.3554 1814.8569 2.736 25.091815.0092 121.56 128.00 2.3721 1815.0092 3.3589 25.081815.1616 120.99 127.99 2.4057 1815.1616 3.5754 25.061815.3138 120.36 127.99 2.4394 1815.3138 3.0328 25.051815.4662 119.87 127.98 2.4371 1815.4662 2.0608 25.041815.6184 119.56 127.97 2.4131 1815.6184 1.6636 25.021815.7709 119.24 127.96 2.3893 1815.7709 1.5722 25.011815.9231 118.17 127.95 2.4018 1815.9231 1.6133 25.001816.0756 114.54 127.95 2.4651 1816.0756 1.6492 24.981816.2278 108.08 127.94 2.6063 1816.2278 1.7503 24.971816.3801 100.51 127.93 2.8122 1816.3801 1.8519 24.961816.5325 93.51 127.92 2.8713 1816.5325 1.651 24.941816.6848 91.35 127.91 2.7271 1816.6848 1.7072 24.931816.8372 93.99 127.91 2.5629 1816.8372 1.7162 24.921816.9895 98.41 127.90 2.4444 1816.9895 1.6935 24.901817.1418 104.56 127.89 2.4111 1817.1418 1.6779 24.891817.2942 111.24 127.88 2.3946 1817.2942 1.6695 24.881817.4465 117.03 127.87 2.3938 1817.4465 1.7649 24.861817.5989 119.50 127.87 2.3941 1817.5989 1.9958 24.851817.7512 119.58 127.86 2.3809 1817.7512 2.1286 24.841817.9036 119.94 127.85 2.3784 1817.9036 2.0913 24.821818.0558 120.44 127.84 2.3736 1818.0558 1.9319 24.811818.2083 120.76 127.83 2.3693 1818.2083 1.7035 24.801818.3605 120.82 127.83 2.3593 1818.3605 1.6632 24.781818.5129 120.38 127.82 2.3646 1818.5129 1.706 24.771818.6652 118.41 127.81 2.3848 1818.6652 1.7163 24.761818.8176 114.04 127.80 2.459 1818.8176 1.7358 24.741818.9698 109.08 127.79 2.5906 1818.9698 1.7893 24.731819.1222 106.35 127.79 2.6937 1819.1222 1.804 24.721819.2745 106.85 127.78 2.6228 1819.2745 1.7866 24.711819.4269 110.97 127.77 2.469 1819.4269 1.7489 24.691819.5792 116.09 127.76 2.3667 1819.5792 1.6733 24.681819.7316 119.26 127.75 2.3631 1819.7316 1.5879 24.671819.8839 120.87 127.75 2.3819 1819.8839 1.5246 24.651820.0361 121.45 127.74 2.3871 1820.0361 1.502 24.641820.1886 121.28 127.73 2.3653 1820.1886 1.59 24.631820.3408 120.75 127.72 2.3626 1820.3408 1.8136 24.611820.4933 120.30 127.71 2.3703 1820.4933 1.733 24.601820.6456 120.31 127.71 2.3746 1820.6456 0.9377 24.591820.7981 120.63 127.70 2.3613 1820.7981 0.6384 24.57



1820.9504 121.09 127.69 2.3582 1820.9504 0.5739 24.561821.1029 121.33 127.68 2.3572 1821.1029 0.6162 24.551821.2552 121.02 127.67 2.3641 1821.2552 0.6982 24.531821.4078 119.93 127.67 2.3592 1821.4078 0.697 24.521821.5602 117.97 127.66 2.3818 1821.5602 0.8197 24.511821.7126 115.86 127.65 2.4307 1821.7126 1.1705 24.491821.865 113.96 127.64 2.5254 1821.865 2.5702 24.48

1822.0173 112.28 127.63 2.671 1822.0173 5.3745 24.471822.1698 110.54 127.63 2.8406 1822.1698 6.6584 24.451822.3221 107.55 127.62 2.9456 1822.3221 5.6723 24.441822.4746 103.17 127.61 3.0336 1822.4746 5.1344 24.431822.627 99.75 127.60 3.1421 1822.627 5.2637 24.41

1822.7794 98.59 127.59 3.2225 1822.7794 5.4982 24.401822.9318 100.55 127.59 3.0164 1822.9318 5.6014 24.391823.0844 105.95 127.58 2.6442 1823.0844 5.2402 24.371823.2367 111.68 127.57 2.4163 1823.2367 4.7579 24.361823.3892 116.79 127.56 2.3096 1823.3892 4.6996 24.351823.5415 119.98 127.55 2.2954 1823.5415 5.0012 24.331823.6938 120.99 127.55 2.299 1823.6938 6.0537 24.321823.8463 121.89 127.54 2.2802 1823.8463 8.4135 24.311823.9987 122.85 127.53 2.2606 1823.9987 11.8444 24.291824.1511 123.72 127.52 2.2481 1824.1511 13.9127 24.281824.3035 124.47 127.51 2.2441 1824.3035 11.8839 24.271824.4559 125.22 127.51 2.2435 1824.4559 8.8304 24.251824.6083 125.92 127.50 2.239 1824.6083 8.4084 24.241824.7609 126.44 127.49 2.2274 1824.7609 10.2622 24.231824.9132 126.66 127.48 2.2048 1824.9132 17.1649 24.221825.0657 126.52 127.47 2.169 1825.0657 35.5194 24.201825.218 126.27 127.47 2.1371 1825.218 61.2075 24.19

1825.3705 126.94 127.46 2.0901 1825.3705 72.7154 24.181825.5228 128.55 127.45 2.0118 1825.5228 73.3632 24.161825.6752 130.26 127.44 1.9586 1825.6752 77.1372 24.151825.8276 131.55 127.43 1.9647 1825.8276 82.8329 24.141825.9801 131.23 127.43 2.0395 1825.9801 88.5154 24.121826.1326 129.14 127.42 2.1001 1826.1326 94.7232 24.111826.2849 126.24 127.41 2.1064 1826.2849 103.7881 24.101826.4374 123.31 127.40 2.0893 1826.4374 108.3376 24.081826.5898 122.25 127.39 2.0853 1826.5898 111.3397 24.071826.7423 122.70 127.39 2.0854 1826.7423 123.4076 24.061826.8947 123.05 127.38 2.0832 1826.8947 138.8506 24.041827.0471 123.43 127.37 2.0898 1827.0471 159.2353 24.031829.3335 133.30 127.25 2.0676 1829.3335 157.8509 23.831829.486 132.35 127.24 2.0742 1829.486 139.5852 23.82

1829.6383 132.05 127.23 2.0742 1829.6383 135.213 23.801829.7908 132.42 127.23 2.0692 1829.7908 131.8756 23.791829.9431 133.48 127.22 2.0561 1829.9431 132.0082 23.781830.0956 135.14 127.21 2.0508 1830.0956 131.6803 23.761830.248 137.22 127.20 2.0539 1830.248 126.9913 23.75



1830.4005 139.14 127.19 2.0536 1830.4005 116.3481 23.741830.5529 140.46 127.19 2.0422 1830.5529 109.7276 23.721830.7053 141.19 127.18 2.0482 1830.7053 96.4492 23.711830.8577 141.31 127.17 2.05 1830.8577 91.4525 23.701831.0101 141.10 127.16 2.0516 1831.0101 98.9225 23.691831.1626 140.70 127.15 2.0379 1831.1626 121.3915 23.671831.3149 140.17 127.15 2.0332 1831.3149 159.567 23.661834.3633 134.69 126.99 2.0635 1834.3633 111.4122 23.391834.5156 134.68 126.98 2.0838 1834.5156 61.0703 23.381834.6681 134.25 126.97 2.0938 1834.6681 24.2287 23.371834.8204 133.48 126.96 2.0898 1834.8204 11.2326 23.351834.973 132.97 126.95 2.086 1834.973 7.2641 23.34

1835.1254 132.56 126.95 1.9445 1835.1254 5.196 23.331835.2777 131.61 126.94 1.6301 1835.2777 4.0781 23.311835.4302 130.00 126.93 1.563 1835.4302 3.4241 23.301835.5825 128.01 126.92 1.6529 1835.5825 3.1296 23.291835.735 126.13 126.91 1.9275 1835.735 3.0205 23.27

1835.8873 125.72 126.91 2.1906 1835.8873 2.926 23.261836.0398 127.49 126.90 2.278 1836.0398 2.9522 23.251836.1921 131.83 126.89 2.276 1836.1921 3.0789 23.231836.3446 137.73 126.88 2.2679 1836.3446 3.2645 23.221836.4969 141.95 126.87 2.2424 1836.4969 3.4146 23.211836.6494 143.05 126.87 2.2254 1836.6494 3.9611 23.201836.8018 139.69 126.86 2.2073 1836.8018 5.3632 23.181836.9541 133.47 126.85 2.1738 1836.9541 9.037 23.171837.1066 128.42 126.84 2.1203 1837.1066 25.7394 23.161837.2589 124.84 126.83 2.0828 1837.2589 58.8549 23.141837.4114 122.83 126.83 2.0711 1837.4114 65.1747 23.131837.5637 122.18 126.82 2.0592 1837.5637 33.7731 23.121837.7162 122.15 126.81 2.0522 1837.7162 11.7541 23.101837.8685 122.26 126.80 2.0644 1837.8685 5.1558 23.091838.021 121.90 126.79 2.1428 1838.021 3.0448 23.08



TABLE 4: Calculation and results based on Eaton Method:

GPob GPob-(GPob-GPn) N Dt/DtRt a/N

Rt GP(Dt) GP(Rt) Depth Ppore(Dt) Depth Ppore(Rt)2.5106 1.03 1.165 0.069 1.200 0.071 1800.0839 3112 1800.0839 75.07

2.52 1.03 1.196 0.079 1.232 0.082 1800.2363 3365 1800.2363 89.182.50 1.03 1.201 0.082 1.237 0.084 1800.3885 3407 1800.3885 92.562.46 1.03 1.172 0.086 1.207 0.088 1800.5409 3166 1800.5409 97.842.42 1.03 1.132 0.082 1.165 0.085 1800.6931 2851 1800.6931 93.172.41 1.03 1.102 0.071 1.135 0.073 1800.8455 2633 1800.8455 78.132.39 1.03 1.083 0.057 1.116 0.058 1800.9977 2503 1800.9977 59.522.39 1.03 1.076 0.050 1.109 0.051 1801.15 2454 1801.15 51.182.39 1.03 1.078 0.060 1.110 0.062 1801.3024 2463 1801.3024 64.252.41 1.03 1.088 0.059 1.120 0.060 1801.4546 2534 1801.4546 62.102.47 1.03 1.120 0.056 1.153 0.057 1801.6069 2762 1801.6069 58.242.55 1.03 1.177 0.055 1.212 0.056 1801.7592 3211 1801.7592 57.112.57 1.03 1.216 0.062 1.253 0.063 1801.9116 3544 1801.9116 65.792.52 1.03 1.200 0.061 1.236 0.062 1802.0638 3406 1802.0638 64.472.46 1.03 1.155 0.059 1.190 0.060 1802.2162 3037 1802.2162 62.002.41 1.03 1.103 0.060 1.136 0.062 1802.3684 2643 1802.3684 63.962.40 1.03 1.068 0.061 1.100 0.063 1802.5208 2397 1802.5208 65.082.38 1.03 1.057 0.061 1.089 0.063 1802.673 2326 1802.673 65.572.37 1.03 1.054 0.060 1.085 0.062 1802.8254 2306 1802.8254 63.952.36 1.03 1.052 0.063 1.083 0.065 1802.9777 2292 1802.9777 67.672.35 1.03 1.051 0.074 1.082 0.076 1803.1299 2285 1803.1299 82.402.35 1.03 1.051 0.087 1.082 0.089 1803.2822 2285 1803.2822 99.062.36 1.03 1.051 0.087 1.083 0.090 1803.4344 2289 1803.4344 100.142.36 1.03 1.052 0.081 1.084 0.083 1803.5869 2298 1803.5869 91.332.37 1.03 1.054 0.068 1.085 0.070 1803.7391 2306 1803.7391 73.852.38 1.03 1.056 0.060 1.088 0.062 1803.8915 2320 1803.8915 63.842.38 1.03 1.064 0.059 1.096 0.061 1804.0437 2373 1804.0437 62.532.39 1.03 1.084 0.060 1.116 0.062 1804.196 2510 1804.196 64.052.42 1.03 1.129 0.064 1.163 0.066 1804.3483 2839 1804.3483 68.922.52 1.03 1.203 0.085 1.240 0.087 1804.5007 3436 1804.5007 96.442.66 1.03 1.257 0.116 1.295 0.120 1804.653 3918 1804.653 141.342.71 1.03 1.265 0.126 1.302 0.129 1804.8052 3988 1804.8052 155.132.65 1.03 1.224 0.118 1.261 0.121 1804.9575 3617 1804.9575 143.392.54 1.03 1.146 0.096 1.181 0.099 1805.1097 2971 1805.1097 112.802.46 1.03 1.096 0.070 1.129 0.072 1805.2622 2600 1805.2622 76.772.42 1.03 1.078 0.062 1.111 0.064 1805.4144 2475 1805.4144 67.092.41 1.03 1.091 0.063 1.124 0.065 1805.5668 2563 1805.5668 67.512.43 1.03 1.144 0.064 1.178 0.066 1805.719 2953 1805.719 69.412.51 1.03 1.226 0.065 1.262 0.067 1805.8713 3633 1805.8713 70.332.64 1.03 1.335 0.066 1.375 0.068 1806.0237 4692 1806.0237 71.262.71 1.03 1.405 0.066 1.447 0.067 1806.176 5472 1806.176 71.072.68 1.03 1.407 0.065 1.449 0.066 1806.3282 5496 1806.3282 69.782.58 1.03 1.359 0.066 1.400 0.068 1806.4806 4954 1806.4806 71.422.49 1.03 1.273 0.071 1.311 0.073 1806.6329 4073 1806.6329 78.652.44 1.03 1.199 0.077 1.235 0.079 1806.7852 3400 1806.7852 85.88



2.42 1.03 1.141 0.074 1.175 0.076 1806.9375 2930 1806.9375 81.932.41 1.03 1.108 0.074 1.142 0.076 1807.0897 2689 1807.0897 82.172.40 1.03 1.097 0.068 1.130 0.070 1807.2422 2606 1807.2422 73.872.38 1.03 1.090 0.056 1.123 0.058 1807.3944 2557 1807.3944 59.382.38 1.03 1.088 0.062 1.120 0.064 1807.5468 2540 1807.5468 66.492.38 1.03 1.088 0.071 1.120 0.074 1807.699 2541 1807.699 78.832.39 1.03 1.089 0.089 1.122 0.092 1807.8514 2554 1807.8514 102.942.41 1.03 1.091 0.095 1.124 0.098 1808.0037 2569 1808.0037 110.932.43 1.03 1.094 0.090 1.127 0.093 1808.156 2585 1808.156 103.992.43 1.03 1.096 0.078 1.129 0.081 1808.3082 2603 1808.3082 88.012.42 1.03 1.098 0.065 1.131 0.067 1808.4607 2614 1808.4607 70.702.40 1.03 1.097 0.063 1.130 0.065 1808.6129 2609 1808.6129 67.682.41 1.03 1.097 0.065 1.130 0.067 1808.7651 2611 1808.7651 70.802.43 1.03 1.106 0.066 1.139 0.068 1808.9175 2671 1808.9175 72.392.48 1.03 1.133 0.067 1.167 0.069 1809.0698 2873 1809.0698 73.542.58 1.03 1.188 0.064 1.224 0.066 1809.2222 3319 1809.2222 69.582.67 1.03 1.248 0.062 1.285 0.064 1809.3744 3842 1809.3744 66.282.65 1.03 1.263 0.062 1.301 0.064 1809.5267 3980 1809.5267 66.372.57 1.03 1.235 0.065 1.272 0.067 1809.6791 3722 1809.6791 70.932.49 1.03 1.183 0.068 1.218 0.070 1809.8314 3273 1809.8314 74.902.42 1.03 1.130 0.063 1.164 0.065 1809.9836 2851 1809.9836 67.792.38 1.03 1.094 0.062 1.126 0.064 1810.136 2587 1810.136 67.072.35 1.03 1.070 0.064 1.102 0.066 1810.2883 2422 1810.2883 69.182.34 1.03 1.054 0.065 1.086 0.067 1810.4406 2318 1810.4406 70.362.33 1.03 1.044 0.063 1.076 0.065 1810.5929 2254 1810.5929 68.162.34 1.03 1.038 0.062 1.070 0.064 1810.7451 2215 1810.7451 67.332.35 1.03 1.034 0.062 1.065 0.064 1810.8975 2186 1810.8975 67.132.36 1.03 1.029 0.061 1.060 0.063 1811.0497 2156 1811.0497 66.032.36 1.03 1.024 0.060 1.055 0.062 1811.202 2128 1811.202 64.712.35 1.03 1.021 0.064 1.051 0.066 1811.3542 2105 1811.3542 69.272.34 1.03 1.020 0.076 1.051 0.078 1811.5066 2101 1811.5066 84.742.34 1.03 1.023 0.084 1.054 0.086 1811.6588 2119 1811.6588 95.952.34 1.03 1.026 0.085 1.057 0.088 1811.8113 2139 1811.8113 98.012.34 1.03 1.028 0.086 1.059 0.089 1811.9635 2150 1811.9635 99.502.35 1.03 1.029 0.079 1.060 0.081 1812.1158 2156 1812.1158 89.172.36 1.03 1.030 0.071 1.061 0.073 1812.2681 2162 1812.2681 77.932.37 1.03 1.031 0.064 1.062 0.065 1812.4203 2170 1812.4203 68.822.38 1.03 1.034 0.064 1.065 0.066 1812.5726 2192 1812.5726 69.912.38 1.03 1.046 0.075 1.077 0.077 1812.7249 2264 1812.7249 83.692.39 1.03 1.069 0.066 1.101 0.068 1812.8772 2421 1812.8772 72.302.40 1.03 1.105 0.065 1.138 0.067 1813.0294 2671 1813.0294 70.822.42 1.03 1.149 0.065 1.184 0.067 1813.1818 3008 1813.1818 71.252.42 1.03 1.174 0.065 1.210 0.067 1813.334 3210 1813.334 71.282.42 1.03 1.167 0.066 1.202 0.068 1813.4865 3146 1813.4865 71.912.40 1.03 1.142 0.068 1.176 0.070 1813.6387 2950 1813.6387 74.092.39 1.03 1.106 0.069 1.139 0.071 1813.791 2681 1813.791 75.962.39 1.03 1.078 0.069 1.110 0.071 1813.9432 2484 1813.9432 76.412.38 1.03 1.061 0.070 1.093 0.072 1814.0956 2368 1814.0956 77.622.38 1.03 1.050 0.070 1.081 0.072 1814.2478 2294 1814.2478 77.592.37 1.03 1.045 0.068 1.076 0.070 1814.4 2263 1814.4 74.552.37 1.03 1.044 0.067 1.075 0.069 1814.5524 2254 1814.5524 73.62



2.36 1.03 1.046 0.080 1.077 0.082 1814.7046 2269 1814.7046 90.502.36 1.03 1.049 0.109 1.080 0.112 1814.8569 2289 1814.8569 131.652.37 1.03 1.053 0.134 1.085 0.138 1815.0092 2315 1815.0092 168.512.39 1.03 1.058 0.143 1.090 0.147 1815.1616 2348 1815.1616 181.752.41 1.03 1.063 0.121 1.095 0.125 1815.3138 2385 1815.3138 149.282.42 1.03 1.068 0.082 1.100 0.085 1815.4662 2414 1815.4662 93.962.42 1.03 1.070 0.066 1.102 0.068 1815.6184 2433 1815.6184 72.732.40 1.03 1.073 0.063 1.105 0.065 1815.7709 2452 1815.7709 68.012.40 1.03 1.083 0.065 1.115 0.066 1815.9231 2519 1815.9231 70.202.43 1.03 1.117 0.066 1.151 0.068 1816.0756 2766 1816.0756 72.132.52 1.03 1.184 0.070 1.219 0.072 1816.2278 3292 1816.2278 77.522.67 1.03 1.273 0.074 1.311 0.076 1816.3801 4093 1816.3801 83.012.77 1.03 1.368 0.066 1.409 0.068 1816.5325 5082 1816.5325 72.382.75 1.03 1.400 0.068 1.442 0.071 1816.6848 5450 1816.6848 75.402.66 1.03 1.361 0.069 1.402 0.071 1816.8372 5003 1816.8372 75.932.55 1.03 1.300 0.068 1.339 0.070 1816.9895 4359 1816.9895 74.782.48 1.03 1.223 0.067 1.260 0.069 1817.1418 3633 1817.1418 74.012.44 1.03 1.150 0.067 1.184 0.069 1817.2942 3017 1817.2942 73.622.42 1.03 1.093 0.071 1.125 0.073 1817.4465 2590 1817.4465 78.752.40 1.03 1.070 0.080 1.102 0.083 1817.5989 2433 1817.5989 91.342.39 1.03 1.069 0.086 1.101 0.088 1817.7512 2428 1817.7512 98.752.39 1.03 1.066 0.084 1.098 0.087 1817.9036 2406 1817.9036 96.742.38 1.03 1.061 0.078 1.093 0.080 1818.0558 2376 1818.0558 88.032.37 1.03 1.059 0.069 1.090 0.071 1818.2083 2357 1818.2083 75.752.37 1.03 1.058 0.067 1.090 0.069 1818.3605 2353 1818.3605 73.662.37 1.03 1.062 0.069 1.094 0.071 1818.5129 2379 1818.5129 75.992.38 1.03 1.079 0.069 1.112 0.071 1818.6652 2499 1818.6652 76.602.42 1.03 1.121 0.070 1.154 0.072 1818.8176 2798 1818.8176 77.702.50 1.03 1.172 0.072 1.207 0.075 1818.9698 3196 1818.9698 80.642.60 1.03 1.202 0.073 1.238 0.075 1819.1222 3449 1819.1222 81.492.61 1.03 1.196 0.072 1.232 0.074 1819.2745 3399 1819.2745 80.612.54 1.03 1.151 0.071 1.186 0.073 1819.4269 3034 1819.4269 78.632.45 1.03 1.101 0.068 1.134 0.070 1819.5792 2650 1819.5792 74.622.41 1.03 1.071 0.064 1.103 0.066 1819.7316 2445 1819.7316 70.132.40 1.03 1.057 0.062 1.089 0.064 1819.8839 2348 1819.8839 66.842.39 1.03 1.052 0.061 1.083 0.063 1820.0361 2314 1820.0361 65.702.38 1.03 1.053 0.065 1.085 0.067 1820.1886 2323 1820.1886 70.392.37 1.03 1.058 0.074 1.089 0.076 1820.3408 2354 1820.3408 82.492.37 1.03 1.062 0.070 1.093 0.073 1820.4933 2380 1820.4933 78.172.37 1.03 1.061 0.038 1.093 0.039 1820.6456 2379 1820.6456 37.442.37 1.03 1.059 0.026 1.090 0.027 1820.7981 2360 1820.7981 23.622.36 1.03 1.055 0.023 1.086 0.024 1820.9504 2333 1820.9504 20.802.36 1.03 1.052 0.025 1.084 0.026 1821.1029 2319 1821.1029 22.672.36 1.03 1.055 0.028 1.087 0.029 1821.2552 2337 1821.2552 26.352.36 1.03 1.065 0.028 1.096 0.029 1821.4078 2401 1821.4078 26.322.37 1.03 1.082 0.033 1.115 0.034 1821.5602 2522 1821.5602 32.002.40 1.03 1.102 0.048 1.135 0.049 1821.7126 2662 1821.7126 49.102.46 1.03 1.120 0.105 1.154 0.108 1821.865 2797 1821.865 126.272.57 1.03 1.137 0.220 1.171 0.226 1822.0173 2924 1822.0173 306.252.70 1.03 1.155 0.272 1.189 0.280 1822.1698 3065 1822.1698 396.302.82 1.03 1.187 0.232 1.222 0.239 1822.3221 3327 1822.3221 327.20



Chart & Results:

y = -0.0287x + 178.65R² = 0.0222

60.00

70.00

80.00

90.00

100.00

110.00

120.00

130.00

140.00

150.00

160.00

1700 1750 1800 1850 1900 1950 2000 2050

Soni

c Lo

g [m

ic-s

/ft]

Depth [m]

DT

DT

Linear (DT)

Fig. A3: Variation of traveltime sonic log vs.depth



y = 0.2542x + 1708.6R² = 0.0003

0

2000

4000

6000

8000

10000

12000

1750 1800 1850 1900 1950 2000 2050

Ppore(Dt)

Ppore(Dt)

Linear (Ppore(Dt))

Fig. A4: Pore pressure predication using Eaton sonic travel time method.



y = -0.0868x + 177.04R² = 0.0634

1

51

101

151

201

251

1700 1750 1800 1850 1900 1950 2000 2050

RT:

RT:

Linear (RT:)

Fig.A5 : Variation of Resistivity Vs. depth



y = -6.4919x + 13725R² = 0.0232

100.00

2100.00

4100.00

6100.00

8100.00

10100.00

12100.00

14100.00

16100.00

18100.00

20100.00

1750 1800 1850 1900 1950 2000 2050

Ppore(Rt)

Ppore(Rt)

Linear (Ppore(Rt))

Fig. A6: Pore pressure predication using Eaton Resistivity method.



Appendix B

Equivalent-Depth Method:Well Name: 6608 10-E-3 HFelt: Norne

GPn10ZP B

B,pore : [Kg/cm 2 ]

10ZP bovb : [Kg/cm 2 ]

: [Kg/cm 2 ]

TABLE 5: WELL DATA AND PRESSURE CALCULATION

PHI TVD PHI RHOB Pob PPore(B) Ppore(A) TVD0.34 2364.685 0.3394 2.3284 550.5933 248.2919 248.2919 2364.6850.34 2364.805 0.3421 2.3202 548.6821 248.3045 248.3045 2364.8050.34 2364.925 0.3444 2.32 548.6626 248.3171 248.3171 2364.9250.31 2366.366 0.3131 2.3157 547.9794 248.4685 248.4685 2366.3660.31 2366.486 0.3084 2.3237 549.9004 248.481 248.481 2366.4860.31 2366.606 0.3056 2.3179 548.5557 248.4937 248.4937 2366.6060.31 2366.726 0.3052 2.31 546.7138 248.5063 248.5063 2366.7260.32 2366.846 0.322 2.31 546.7415 248.5189 248.5189 2366.8460.32 2366.967 0.3183 2.3219 549.586 248.5315 248.5315 2366.9670.32 2367.087 0.3238 2.3475 555.6736 248.5441 248.5441 2367.0870.26 2556.64 0.2631 2.3606 603.5205 268.4472 268.4472 2556.640.26 2556.761 0.2645 2.3665 605.0574 268.4599 268.4599 2556.7610.26 2556.881 0.2636 2.3655 604.8302 268.4725 268.4725 2556.8810.34 2562.775 0.3445 2.3843 611.0425 269.0914 308.7411 2562.7750.34 2562.895 0.3383 2.3936 613.4546 269.104 311.1533 2562.8950.34 2563.016 0.3397 2.395 613.8422 269.1166 311.5409 2563.0160.34 2563.136 0.3403 2.3877 612 269.1293 309.6986 2563.1360.34 2563.256 0.3435 2.3803 610.1318 269.1419 307.8305 2563.2560.34 2563.377 0.3446 2.3721 608.0585 269.1545 305.7572 2563.3770.34 2563.497 0.3431 2.373 608.3178 269.1672 306.0164 2563.4970.34 2563.617 0.3449 2.3771 609.3974 269.1798 307.0961 2563.6170.32 2564.219 0.323 2.3809 610.5148 269.2429 312.2921 2564.2190.32 2564.339 0.3164 2.3779 609.7741 269.2556 311.5515 2564.3390.32 2564.459 0.3163 2.375 609.0591 269.2682 310.8364 2564.4590.31 2564.579 0.3111 2.38 610.3699 269.2808 310.8589 2564.5790.31 2564.7 0.3074 2.3743 608.9366 269.2935 309.4257 2564.70.34 2567.827 0.3359 2.3858 612.6322 269.6218 310.3308 2567.8270.34 2567.948 0.338 2.3784 610.7606 269.6345 308.4593 2567.9480.31 2574.564 0.3103 2.4093 620.2896 270.3292 320.7786 2574.564

B,ovbA,ovbB,poreA,pore PPPP



0.31 2574.684 0.309 2.4011 618.2073 270.3418 318.6963 2574.6840.26 2624.337 0.2643 2.1571 566.0957 275.5554 231.0224 2624.3370.26 2624.457 0.2576 2.1638 567.8801 275.568 232.8068 2624.4570.26 2624.577 0.2552 2.1728 570.2682 275.5806 235.1949 2624.5770.26 2624.698 0.2554 2.1597 566.8559 275.5932 231.7826 2624.6980.26 2625.9 0.261 2.1061 553.0407 275.7195 217.9674 2625.90.26 2626.02 0.2554 2.0997 551.3854 275.7321 216.3121 2626.020.26 2640.445 0.2642 2.2725 600.0411 277.2467 264.9678 2640.4450.26 2640.565 0.2613 2.2738 600.4117 277.2593 265.3384 2640.5650.26 2688.798 0.2586 2.3029 619.2033 282.3238 284.13 2688.7980.26 2688.918 0.2599 2.3111 621.4358 282.3364 286.3625 2688.9180.26 2690.595 0.2634 2.263 608.8817 282.5125 273.8084 2690.5950.26 2690.715 0.2609 2.26 608.1015 282.5251 273.0283 2690.7150.26 2714.275 0.263 2.1695 588.862 284.9989 253.7887 2714.2750.26 2714.395 0.2614 2.1708 589.2408 285.0114 254.1675 2714.3950.26 2719.532 0.2566 2.2062 599.9831 285.5508 264.9098 2719.5320.26 2719.651 0.2648 2.2204 603.8713 285.5634 268.798 2719.6510.26 2748.604 0.2634 2.354 647.0214 288.6034 311.9481 2748.6040.26 2748.723 0.2636 2.5382 697.6808 288.6159 362.6076 2748.7230.26 2753.841 0.2621 2.1626 595.5456 289.1533 260.4723 2753.8410.26 2753.96 0.2639 2.1511 592.4043 289.1658 257.331 2753.960.26 2754.079 0.2611 2.1463 591.1079 289.1783 256.0346 2754.0790.26 2771.293 0.2628 2.2497 623.4577 290.9857 288.3844 2771.2930.26 2771.411 0.2607 2.2305 618.1633 290.9982 283.09 2771.4110.26 2776.989 0.2648 2.2511 625.1279 291.5838 290.0547 2776.9890.26 2777.107 0.2566 2.215 615.1293 291.5963 280.056 2777.1070.26 2782.091 0.2612 2.2911 637.4049 292.1196 302.3316 2782.0910.26 2782.21 0.2637 2.2788 634.01 292.1321 298.9367 2782.210.26 2782.329 0.2633 2.2837 635.4004 292.1445 300.3271 2782.3290.32 2803.067 0.3182 2.6474 742.084 294.322 443.8613 2803.0670.32 2803.186 0.3212 2.6031 729.6973 294.3345 431.4746 2803.1860.26 2809.347 0.2555 2.2639 636.008 294.9814 300.9347 2809.3470.26 2809.465 0.2605 2.3164 650.7845 294.9939 315.7113 2809.4650.26 2810.532 0.2588 2.2758 639.6208 295.1058 304.5475 2810.5320.26 2810.65 0.2578 2.2496 632.2838 295.1182 297.2105 2810.650.26 2810.769 0.263 2.2193 623.7939 295.1307 288.7206 2810.7690.26 2810.887 0.2602 2.1995 618.2546 295.1431 283.1813 2810.8870.26 2812.072 0.2629 2.1772 612.2443 295.2675 277.171 2812.0720.26 2812.19 0.2559 2.195 617.2757 295.28 282.2025 2812.190.26 2814.44 0.2559 2.3836 670.85 295.5162 335.7767 2814.440.26 2814.559 0.2575 2.4075 677.605 295.5287 342.5317 2814.5590.26 2817.99 0.259 2.4789 698.5516 295.889 363.4783 2817.990.26 2818.108 0.2614 2.4862 700.6381 295.9014 365.5648 2818.1080.26 2819.765 0.258 2.4543 692.0549 296.0753 356.9817 2819.7650.26 2819.884 0.2642 2.4559 692.5352 296.0878 357.4619 2819.8840.26 2820.002 0.2614 2.4529 691.7182 296.1002 356.6449 2820.0020.26 2820.83 0.261 2.2222 626.8449 296.1872 291.7716 2820.830.26 2820.949 0.2636 2.2178 625.63 296.1996 290.5567 2820.949



0.26 2825.09 0.2557 2.4566 694.0116 296.6344 358.9383 2825.090.26 2825.208 0.2643 2.4673 697.0636 296.6469 361.9904 2825.2080.26 2826.036 0.2592 2.4817 701.3375 296.7338 366.2642 2826.0360.26 2826.155 0.2566 2.4818 701.3951 296.7463 366.3218 2826.1550.26 2826.273 0.2569 2.4815 701.3397 296.7587 366.2664 2826.2730.26 2826.51 0.2556 2.4828 701.7659 296.7835 366.6926 2826.510.26 2826.746 0.2649 2.4833 701.9659 296.8084 366.8926 2826.7460.26 2826.865 0.2553 2.4898 703.8328 296.8208 368.7595 2826.8650.26 2826.983 0.2593 2.4921 704.5125 296.8332 369.4392 2826.9830.26 2827.101 0.2614 2.488 703.3828 296.8456 368.3095 2827.1010.26 2831.361 0.264 2.4964 706.821 297.2929 371.7477 2831.3610.26 2831.48 0.2565 2.4862 703.9624 297.3053 368.8891 2831.480.26 2857.853 0.2575 2.4345 695.7444 300.0746 360.6711 2857.8530.26 2857.971 0.2573 2.4312 694.83 300.087 359.7567 2857.9710.26 2858.681 0.2596 2.479 708.6669 300.1615 373.5937 2858.6810.26 2858.799 0.2565 2.4458 699.205 300.1739 364.1317 2858.7990.26 2858.917 0.2589 2.4273 693.9449 300.1863 358.8716 2858.9170.26 2859.035 0.2575 2.4098 688.9704 300.1987 353.8971 2859.0350.26 2863.524 0.2624 2.3924 685.0695 300.67 349.9962 2863.5240.26 2863.642 0.2592 2.4024 687.9614 300.6824 352.8881 2863.6420.26 2863.76 0.255 2.403 688.1616 300.6948 353.0883 2863.760.26 2865.532 0.2555 2.4166 692.4843 300.8808 357.4111 2865.5320.26 2865.65 0.2558 2.4387 698.846 300.8932 363.7727 2865.650.26 2865.768 0.2592 2.4508 702.3423 300.9056 367.269 2865.7680.26 2865.886 0.2628 2.4299 696.3816 300.918 361.3083 2865.8860.26 2866.004 0.2613 2.4258 695.2352 300.9304 360.1619 2866.0040.26 2867.893 0.2616 2.2872 655.9445 301.1288 320.8712 2867.8930.26 2868.011 0.2596 2.3051 661.1052 301.1412 326.0319 2868.0110.31 2879.582 0.3098 2.4437 703.6835 302.3561 404.1725 2879.5820.31 2879.7 0.3107 2.4322 700.4007 302.3685 400.8897 2879.70.31 2879.818 0.3082 2.4239 698.0391 302.3809 398.5281 2879.8180.31 2879.936 0.308 2.4126 694.8134 302.3933 395.3024 2879.9360.31 2880.054 0.3093 2.4039 692.3362 302.4057 392.8252 2880.0540.31 2880.172 0.3104 2.3907 688.5627 302.418 389.0517 2880.1720.31 2880.29 0.3096 2.3664 681.5918 302.4304 382.0808 2880.290.31 2880.408 0.306 2.3795 685.3931 302.4428 385.8821 2880.4080.31 2880.88 0.3082 2.3626 680.6366 302.4924 381.1256 2880.880.31 2880.998 0.305 2.352 677.6106 302.5047 378.0997 2880.9980.31 2881.234 0.3141 2.353 677.9543 302.5295 378.4433 2881.2340.31 2881.352 0.3105 2.3895 688.499 302.5419 388.988 2881.3520.31 2881.47 0.3057 2.4433 704.0294 302.5543 404.5185 2881.470.31 2882.531 0.309 2.3924 689.6168 302.6658 390.1058 2882.5310.31 2882.649 0.3106 2.4 691.8358 302.6782 392.3248 2882.6490.31 2882.767 0.3113 2.3921 689.5867 302.6905 390.0757 2882.7670.31 2884.065 0.3107 2.3193 668.9011 302.8268 369.3902 2884.0650.31 2884.183 0.3097 2.2906 660.6509 302.8392 361.1399 2884.1830.31 2884.301 0.3089 2.2619 652.3999 302.8516 352.889 2884.3010.34 2884.89 0.3392 2.2843 658.9955 302.9135 356.6942 2884.89



0.34 2885.008 0.3417 2.3204 669.4373 302.9259 367.136 2885.0080.34 2885.126 0.3402 2.3507 678.2066 302.9383 375.9053 2885.1260.31 2886.306 0.3096 2.2768 657.1541 303.0621 357.6432 2886.3060.31 2886.424 0.3085 2.275 656.6614 303.0745 357.1504 2886.4240.31 2886.542 0.3145 2.2885 660.5851 303.0869 361.0741 2886.5420.31 2887.25 0.3081 2.2263 642.7884 303.1612 343.2774 2887.250.31 2887.367 0.309 2.1897 632.2468 303.1736 332.7359 2887.3670.31 2887.486 0.3137 2.1902 632.4171 303.186 332.9061 2887.4860.34 2887.721 0.3418 2.3017 664.6668 303.2107 362.3655 2887.7210.34 2887.839 0.3427 2.3429 676.5919 303.2231 374.2905 2887.8390.34 2887.957 0.3419 2.369 684.1571 303.2355 381.8557 2887.9570.34 2888.075 0.3439 2.385 688.8059 303.2479 386.5046 2888.0750.34 2888.193 0.341 2.398 692.5888 303.2603 390.2874 2888.1930.34 2888.311 0.335 2.3775 686.696 303.2727 384.3947 2888.3110.34 2888.429 0.3373 2.3236 671.1554 303.2851 368.8541 2888.4290.32 2888.665 0.3248 1.8889 545.6399 303.3098 247.4173 2888.6650.32 2888.783 0.318 1.854 535.5804 303.3222 237.3577 2888.7830.32 2888.901 0.3213 2.0785 600.4581 303.3346 302.2354 2888.9010.32 2889.019 0.3178 2.1875 631.9729 303.347 333.7503 2889.0190.32 2889.137 0.3196 2.2246 642.7174 303.3594 344.4948 2889.1370.32 2889.255 0.3177 2.2314 644.7083 303.3718 346.4857 2889.2550.31 2889.373 0.3127 2.2437 648.2886 303.3841 348.7776 2889.3730.31 2889.491 0.3129 2.2812 659.1506 303.3965 359.6396 2889.4910.31 2889.609 0.3095 2.2968 663.6854 303.4089 364.1744 2889.6090.31 2890.788 0.3062 2.5448 735.6478 303.5328 436.1368 2890.7880.31 2890.906 0.3122 2.4948 721.2233 303.5452 421.7123 2890.9060.32 2891.024 0.32 2.4629 712.0304 303.5576 413.8078 2891.0240.32 2891.142 0.3203 2.441 705.7278 303.5699 407.5052 2891.1420.32 2891.26 0.3165 2.4215 700.1187 303.5823 401.896 2891.260.31 2891.378 0.3134 2.4035 694.9428 303.5947 395.4318 2891.3780.31 2891.496 0.3128 2.397 693.0916 303.6071 393.5806 2891.4960.32 2891.614 0.3177 2.4003 694.0741 303.6195 395.8515 2891.6140.32 2891.732 0.3226 2.4055 695.6062 303.6319 397.3835 2891.7320.32 2891.85 0.3216 2.4192 699.5964 303.6443 401.3737 2891.850.32 2891.968 0.3214 2.4317 703.2399 303.6566 405.0172 2891.9680.32 2892.204 0.3211 2.4208 700.1447 303.6814 401.9221 2892.2040.32 2892.322 0.3181 2.4215 700.3758 303.6938 402.1531 2892.3220.32 2892.44 0.3233 2.4152 698.5821 303.7062 400.3594 2892.440.32 2892.676 0.3202 2.3618 683.1922 303.731 384.9695 2892.6760.32 2892.794 0.3181 2.3216 671.591 303.7433 373.3683 2892.7940.31 2892.912 0.3058 2.2814 659.9889 303.7557 360.4779 2892.9120.31 2893.03 0.3062 2.2512 651.2789 303.7681 351.7679 2893.030.26 2893.619 0.2635 2.2163 641.3129 303.83 306.2396 2893.6190.26 2893.738 0.2776 2.2354 646.8661 303.8424 311.7928 2893.738



Results & Charts:

Well: N6608 10-E-3 H

Felt: Norne

2200

2300

2400

2500

2600

2700

2800

2900

3000

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90

Depth-Porosity

Fig.B1 : variation of porosity vs. depth in Norne felt well nr: N6608 10-E-3 H

2200

2300

2400

2500

2600

2700

2800

2900

3000

0 50 100 150 200 250 300 350 400 450 500

PorePressure(Eq.Depth-Method)

Fig. B2: Predication of pore pressure using equivalent depth method.



Appendix C

Vertical-Horizontal Method:

Well Name: 34 10-C-11Felt: Gulfaks

Fig. C1: Principle of predication pore pressure in Horizontal & Vertical Methods.



TABLE 6: Well data & calculation:

GPn=1.05

Vertical Method:

Horizontal Method:x


x=3, & x=2,…..

[kg/cm2] [kg/cm2]

Vp TVD RHOB Pob Pp,n Ppore(vertical) TVD N trend (vp) Ppore(Horizontal) TVD

665.97 1940.094 2.048 397.33 203.7098 182.6348025 1940.094 655.413597 212.77 1940.094

666.57 1940.246 2.036 395.03 203.7258 180.5468925 1940.246 654.90355 213.60 1940.246

660.06 1940.398 2.015 390.99 203.7418 174.4039964 1940.398 654.393503 208.52 1940.398

661.82 1940.55 2.005 389.08 203.7578 173.0880003 1940.55 653.884126 210.35 1940.55

664.78 1940.702 2 388.14 203.7737 173.1266605 1940.702 653.374749 213.10 1940.702

664.78 1940.854 2.011 390.31 203.7897 175.3088171 1940.854 652.865372 213.64 1940.854

667.17 1941.007 2.009 389.95 203.8057 175.7371658 1941.007 652.355325 215.93 1941.007

661.23 1941.159 2.001 388.43 203.8217 172.3088158 1941.159 651.845613 211.57 1941.159

655.98 1941.311 1.998 387.87 203.8377 170.0433764 1941.311 651.336236 207.72 1941.311

655.40 1941.463 2.01 390.23 203.8536 172.2283648 1941.463 650.826859 207.73 1941.463

650.81 1941.616 2.037 395.51 203.8696 175.9805038 1941.616 650.316477 204.30 1941.616

648.54 1941.768 2.058 399.62 203.8856 179.3376119 1941.768 649.806765 202.73 1941.768

653.10 1941.92 2.064 400.81 203.9016 182.0889009 1941.92 649.297388 207.32 1941.92

651.95 1942.072 2.037 395.60 203.9176 176.5094734 1942.072 648.787676 206.69 1942.072

652.52 1942.224 2.032 394.66 203.9336 175.7786421 1942.224 648.277294 207.63 1942.224

711.22 1942.377 2.057 399.55 203.9495 198.7451632 1942.377 647.767917 251.77 1942.377

716.71 1942.529 2.104 408.71 203.9655 209.4591636 1942.529 647.258205 257.90 1942.529

732.24 1942.681 2.108 409.52 203.9815 214.5106289 1942.681 646.748828 267.89 1942.681

734.41 1942.833 2.082 404.50 203.9975 210.0828917 1942.833 646.239116 267.89 1942.833

668.97 1942.985 2.065 401.23 204.0135 187.8094747 1942.985 645.728734 223.86 1942.985

668.37 1943.138 2.072 402.62 204.0294 189.025655 1943.138 645.219357 223.96 1943.138

664.19 1943.29 2.059 400.12 204.0454 185.2031099 1943.29 644.709645 220.79 1943.29

660.06 1943.442 2.041 396.66 204.0614 180.4087798 1943.442 644.200268 217.61 1943.442

651.38 1943.594 2.025 393.58 204.0774 174.4665683 1943.594 643.689886 210.71 1943.594

662.41 1943.746 2.045 397.50 204.0934 182.0503427 1943.746 643.180509 220.45 1943.746

673.21 1943.898 2.084 405.11 204.1093 193.1356233 1943.898 642.671132 230.24 1943.898

676.27 1944.051 2.1 408.25 204.1253 197.254326 1944.051 642.161085 233.48 1944.051

672.60 1944.203 2.067 401.87 204.1413 189.7351818 1944.203 641.651038 230.20 1944.203

661.82 1944.355 2.023 393.34 204.1573 177.7727866 1944.355 641.141661 221.34 1944.355

659.47 1944.507 2 388.90 204.1733 172.5802933 1944.507 640.631949 219.56 1944.507

DD)PP(PP e

n,peovbpore



655.98 1944.659 1.999 388.74 204.1892 171.2815868 1944.659 640.122572 217.25 1944.659

662.41 1944.812 2.01 390.91 204.2052 175.5794209 1944.812 639.61286 222.83 1944.812

670.78 1944.964 2.039 396.58 204.2212 183.9539182 1944.964 639.102478 230.21 1944.964

674.43 1945.116 2.064 401.47 204.2372 190.0156775 1945.116 638.593101 234.04 1945.116

676.27 1945.268 2.083 405.20 204.2532 194.3352437 1945.268 638.083389 236.41 1945.268

681.86 1945.42 2.09 406.59 204.2691 197.4719368 1945.42 637.574012 241.18 1945.42

677.51 1945.573 2.093 407.21 204.2852 196.7611025 1945.573 637.063295 238.50 1945.573

668.37 1945.725 2.075 403.74 204.3011 190.4297137 1945.725 636.553918 231.45 1945.725

665.38 1945.877 2.054 399.68 204.3171 185.4325655 1945.877 636.044541 229.03 1945.877

666.57 1946.029 2.044 397.77 204.3331 183.9182104 1946.029 635.534829 230.11 1946.029

672.60 1946.181 2.052 399.36 204.349 187.4407846 1946.181 635.025452 235.24 1946.181

678.12 1946.334 2.068 402.50 204.3651 192.3287702 1946.334 634.514735 240.19 1946.334

685.00 1946.486 2.084 405.65 204.381 197.6002249 1946.486 634.005358 246.07 1946.486

699.18 1946.638 2.097 408.21 204.397 204.3970005 1946.638 633.495981 256.61 1946.638

698.52 1946.79 2.111 410.97 204.413 206.9786772 1946.79 632.986269 257.26 1946.79

689.45 1946.943 2.12 412.75 204.429 206.0952959 1946.943 632.476222 251.92 1946.943

692.02 1947.095 2.113 411.42 204.445 205.5475245 1947.095 631.96651 253.79 1947.095

687.53 1947.247 2.107 410.28 204.4609 203.0857157 1947.247 631.457133 250.83 1947.247

679.99 1947.399 2.108 410.51 204.4769 201.0289243 1947.399 630.947086 245.92 1947.399

679.99 1947.552 2.11 410.93 204.4929 201.4669823 1947.552 630.43704 246.41 1947.552

690.09 1947.704 2.111 411.16 204.5089 204.7763557 1947.704 629.927328 253.98 1947.704

686.90 1947.856 2.12 412.95 204.5249 205.6196032 1947.856 629.41795 252.59 1947.856

683.74 1948.008 2.113 411.61 204.5409 203.3465853 1948.008 628.907904 250.47 1948.008

683.74 1948.16 2.099 408.92 204.5568 200.6676308 1948.16 628.398526 250.27 1948.16

675.04 1948.313 2.086 406.42 204.5728 195.5012322 1948.313 627.88848 243.99 1948.313

681.23 1948.465 2.096 408.40 204.5888 199.4135262 1948.465 627.378768 249.20 1948.465

697.21 1948.617 2.117 412.52 204.6048 208.3423594 1948.617 626.86939 261.40 1948.617

703.81 1948.769 2.142 417.43 204.6207 215.1777554 1948.769 626.359678 267.43 1948.769

713.27 1948.921 2.164 421.75 204.6367 222.1950076 1948.921 625.849297 275.08 1948.921

717.40 1949.074 2.179 424.70 204.6527 226.3161964 1949.074 625.339585 278.96 1949.074

713.95 1949.226 2.195 427.86 204.6687 228.5262606 1949.226 624.830208 278.25 1949.226

713.95 1949.378 2.202 429.25 204.6847 229.9398833 1949.378 624.320496 279.09 1949.378

703.81 1949.53 2.2 428.90 204.7007 226.7275116 1949.53 623.810114 272.79 1949.53

699.18 1949.683 2.186 426.20 204.7167 222.7072474 1949.683 623.300402 269.28 1949.683

695.25 1949.835 2.17 423.11 204.7326 218.4882179 1949.835 622.791025 266.14 1949.835

704.48 1949.987 2.152 419.64 204.7486 217.7070093 1949.987 622.281648 271.53 1949.987

711.22 1950.139 2.151 419.47 204.7646 219.474445 1950.139 621.771936 276.01 1950.139

708.51 1950.291 2.16 421.26 204.7806 220.5127801 1950.291 621.261554 275.31 1950.291

709.18 1950.444 2.172 423.64 204.7966 223.0933129 1950.444 620.751842 276.88 1950.444

698.52 1950.596 2.167 422.69 204.8125 219.1052438 1950.596 620.242465 270.16 1950.596

692.66 1950.748 2.155 420.39 204.8285 215.0914125 1950.748 619.732753 266.00 1950.748



690.73 1950.9 2.148 419.05 204.8445 213.2007874 1950.9 619.222706 264.72 1950.9

683.74 1951.052 2.148 419.09 204.8605 211.1453978 1951.052 618.712659 260.35 1951.052

685.00 1951.205 2.146 418.73 204.8765 211.1867244 1951.205 618.203282 261.53 1951.205

686.90 1951.357 2.147 418.96 204.8925 212.004622 1951.357 617.69357 263.29 1951.357

683.11 1951.509 2.153 420.16 204.9084 212.077077 1951.509 617.183523 261.41 1951.509

694.60 1951.661 2.167 422.93 204.9244 218.3007337 1951.661 616.673476 270.37 1951.661

700.49 1951.813 2.173 424.13 204.9404 221.2418939 1951.813 616.164099 274.95 1951.813

706.49 1951.966 2.173 424.16 204.9564 223.0118393 1951.966 615.654387 279.10 1951.966

706.49 1952.118 2.172 424.00 204.9724 222.8655162 1952.118 615.144675 279.42 1952.118

705.15 1952.27 2.168 423.25 204.9884 221.7511392 1952.27 614.633958 278.71 1952.27

706.49 1952.422 2.175 424.65 205.0044 223.5490541 1952.422 614.124581 280.38 1952.422

711.90 1952.575 2.181 425.86 205.0203 226.298657 1952.575 613.614869 284.44 1952.575

709.86 1952.727 2.187 427.06 205.0363 226.9457996 1952.727 613.105157 284.01 1952.727

713.95 1952.879 2.192 428.07 205.0523 229.1180504 1952.879 612.594441 287.19 1952.879

714.64 1953.031 2.186 426.93 205.0683 228.186291 1953.031 612.085064 287.53 1953.031

707.83 1953.184 2.185 426.77 205.0843 226.1290553 1953.184 611.575352 283.78 1953.184

709.18 1953.336 2.18 425.83 205.1003 225.5835951 1953.336 611.06564 284.62 1953.336

705.15 1953.488 2.179 425.67 205.1163 224.2908138 1953.488 610.555258 282.50 1953.488

706.49 1953.64 2.182 426.28 205.1322 225.3080839 1953.64 610.045546 283.90 1953.64

705.82 1953.793 2.178 425.54 205.1482 224.3844792 1953.793 609.535834 283.59 1953.793

703.14 1953.945 2.173 424.59 205.1642 222.6924624 1953.945 609.026122 282.01 1953.945

692.02 1954.097 2.173 424.63 205.1802 219.4944781 1954.097 608.516745 275.42 1954.097

690.09 1954.249 2.179 425.83 205.1962 220.1433993 1954.249 608.006028 274.93 1954.249

687.53 1954.402 2.179 425.86 205.2122 219.428867 1954.402 607.496316 273.65 1954.402

681.86 1954.554 2.159 421.99 205.2281 213.8506042 1954.554 606.986604 269.08 1954.554

682.48 1954.706 2.149 420.07 205.2441 212.1360184 1954.706 606.477227 269.32 1954.706

679.36 1954.858 2.16 422.25 205.2601 213.3809982 1954.858 605.96651 268.27 1954.858

681.23 1955.011 2.194 428.93 205.2761 220.6500745 1955.011 605.456798 271.92 1955.011

671.99 1955.163 2.226 435.22 205.2921 224.0929932 1955.163 604.947421 267.47 1955.163

663.00 1955.315 2.227 435.45 205.3081 221.4758737 1955.315 604.437709 261.07 1955.315

658.89 1955.467 2.174 425.12 205.3241 209.826672 1955.467 603.926993 255.87 1955.467

661.23 1955.62 2.116 413.81 205.3401 199.2975321 1955.62 603.417281 255.38 1955.62

651.95 1955.772 2.089 408.56 205.356 191.0127807 1955.772 602.907904 247.85 1955.772

658.30 1955.924 2.097 410.16 205.372 194.7253706 1955.924 602.397857 253.24 1955.924

652.52 1956.076 2.109 412.54 205.388 195.2135399 1956.076 601.888145 249.97 1956.076

652.52 1956.229 2.115 413.74 205.404 196.4365643 1956.229 601.377763 250.65 1956.229

657.14 1956.381 2.137 418.08 205.42 202.3160666 1956.381 600.868386 255.51 1956.381

658.30 1956.533 2.149 420.46 205.436 205.0949647 1956.533 600.358339 257.36 1956.533

667.77 1956.685 2.156 421.86 205.4519 209.56625 1956.685 599.848627 265.00 1956.685

679.36 1956.838 2.164 423.46 205.4679 214.8051169 1956.838 599.338245 273.79 1956.838

727.23 1956.99 2.242 438.76 205.4839 243.8502402 1956.99 598.828198 308.51 1956.99



861.21 1957.142 2.395 468.74 205.4999 304.1646727 1957.142 598.318486 380.47 1957.142

914.18 1957.294 2.518 492.85 205.5159 337.8229109 1957.294 597.808774 412.50 1957.294

908.59 1957.447 2.403 470.37 205.5319 314.4095829 1957.447 597.298058 395.13 1957.447

805.23 1957.599 2.238 438.11 205.5479 262.1397092 1957.599 596.788346 343.43 1957.599

703.81 1957.751 2.17 424.83 205.5639 223.5203661 1957.751 596.278634 291.49 1957.751

693.31 1957.904 2.167 424.28 205.5799 219.9320221 1957.904 595.768252 285.51 1957.904

705.15 1958.056 2.175 425.88 205.5959 224.978409 1958.056 595.25854 293.36 1958.056

716.02 1958.208 2.191 429.04 205.6119 231.2101059 1958.208 594.747823 300.99 1958.208

735.14 1958.361 2.24 438.67 205.6279 246.000517 1958.361 594.238111 315.58 1958.361

742.48 1958.513 2.277 445.95 205.6438 255.2019622 1958.513 593.728399 323.07 1958.513

730.80 1958.665 2.229 436.59 205.6598 242.8013202 1958.665 593.218687 313.07 1958.665

713.27 1958.817 2.153 421.73 205.6758 223.2003554 1958.817 592.707971 297.76 1958.817

685.00 1958.97 2.121 415.50 205.6918 208.7879007 1958.97 592.198259 279.93 1958.97

683.74 1959.122 2.162 423.56 205.7078 216.4878922 1959.122 591.688547 282.38 1959.122

686.90 1959.274 2.209 432.80 205.7238 226.6981406 1959.274 591.178835 288.04 1959.274

699.83 1959.427 2.231 437.15 205.7398 234.8682898 1959.427 590.668118 298.02 1959.427

699.83 1959.579 2.239 438.75 205.7558 236.4858745 1959.579 590.158406 299.03 1959.579

701.82 1959.731 2.242 439.37 205.7718 237.6952551 1959.731 589.648359 300.83 1959.731

698.52 1959.883 2.23 437.05 205.7877 234.4412463 1959.883 589.138647 298.30 1959.883

703.14 1960.035 2.211 433.36 205.8037 232.0999877 1960.035 588.628935 299.86 1960.035

702.48 1960.188 2.192 429.67 205.8197 228.2349224 1960.188 588.118218 298.32 1960.188

707.83 1960.34 2.209 433.04 205.8357 233.1398419 1960.34 587.608171 303.06 1960.34

706.49 1960.492 2.245 440.13 205.8517 239.8663072 1960.492 587.098459 305.68 1960.492

704.48 1960.645 2.275 446.05 205.8677 245.2272083 1960.645 586.588413 307.39 1960.645

712.58 1960.797 2.279 446.87 205.8837 248.3461178 1960.797 586.078031 312.79 1960.797

739.53 1960.949 2.272 445.53 205.8997 254.2559636 1960.949 585.568319 326.57 1960.949

768.59 1961.102 2.272 445.56 205.9157 261.5372346 1961.102 585.058272 339.86 1961.102

769.38 1961.254 2.243 439.91 205.9316 256.0890597 1961.254 584.54856 337.30 1961.254

752.25 1961.406 2.208 433.08 205.9477 245.0867695 1961.406 584.038178 326.78 1961.406

718.79 1961.559 2.192 429.97 205.9636 233.2447736 1961.559 583.528131 310.12 1961.559

705.82 1961.711 2.201 431.77 205.9796 231.4445554 1961.711 583.018419 304.52 1961.711

717.40 1961.863 2.211 433.77 205.9956 236.689746 1961.863 582.508372 311.83 1961.863

743.22 1962.015 2.206 432.82 206.0116 242.60572 1962.015 581.998326 323.91 1962.015

769.38 1962.168 2.209 433.44 206.0276 249.709912 1962.168 581.487609 335.27 1962.168

784.82 1962.32 2.213 434.26 206.0436 254.1564819 1962.32 580.977562 341.68 1962.32

783.99 1962.472 2.24 439.59 206.0596 259.3129278 1962.472 580.46785 344.81 1962.472

741.00 1962.625 2.255 442.57 206.0756 251.8467381 1962.625 579.957803 329.19 1962.625

731.52 1962.777 2.278 447.12 206.0916 253.9387908 1962.777 579.447086 327.33 1962.777

722.98 1962.929 2.284 448.33 206.1076 252.884988 1962.929 578.93704 323.96 1962.929

727.23 1963.082 2.329 457.20 206.1236 262.9098006 1963.082 578.426993 330.86 1963.082

783.17 1963.234 2.408 472.75 206.1396 292.3470907 1963.234 577.917281 365.62 1963.234



770.18 1963.387 2.48 486.92 206.1556 303.4932067 1963.387 577.406229 368.61 1963.387

777.43 1963.539 2.423 475.77 206.1716 294.0639092 1963.539 576.896517 365.61 1963.539

775.81 1963.691 2.35 461.47 206.1876 279.4001505 1963.691 576.38647 356.78 1963.691

714.64 1963.843 2.306 452.86 206.2035 255.2265783 1963.843 575.876423 323.79 1963.843

713.27 1963.996 2.301 451.92 206.2195 253.9152932 1963.996 575.366711 322.95 1963.996

712.58 1964.148 2.286 449.00 206.2356 250.8299492 1964.148 574.85566 321.55 1964.148

713.95 1964.3 2.303 452.38 206.2515 254.5996529 1964.3 574.345948 324.24 1964.3

726.51 1964.453 2.331 457.91 206.2675 263.5703806 1964.453 573.836236 333.91 1964.453

730.08 1964.605 2.353 462.27 206.2835 268.8932179 1964.605 573.325854 338.30 1964.605

738.79 1964.757 2.331 457.98 206.2995 266.9012651 1964.757 572.815472 340.67 1964.757

741.74 1964.91 2.353 462.34 206.3155 272.0344526 1964.91 572.30509 344.74 1964.91

730.80 1965.062 2.405 472.60 206.3315 279.4549196 1965.062 571.795378 345.06 1965.062

721.58 1965.214 2.423 476.17 206.3475 280.5755521 1965.214 571.285666 342.27 1965.214

720.18 1965.367 2.363 464.42 206.3635 268.4560885 1965.367 570.774615 335.95 1965.367

730.80 1965.519 2.296 451.28 206.3795 258.1865806 1965.519 570.264903 334.92 1965.519

732.96 1965.671 2.282 448.57 206.3955 256.0545339 1965.671 569.754521 334.82 1965.671

739.53 1965.824 2.296 451.35 206.4115 260.5652245 1965.824 569.244809 339.64 1965.824

745.46 1965.976 2.314 454.93 206.4274 265.6725885 1965.976 568.735097 344.57 1965.976

730.08 1966.128 2.311 454.37 206.4435 261.1471206 1966.128 568.224046 337.48 1966.128

722.28 1966.281 2.301 452.44 206.4595 257.143562 1966.281 567.714334 332.99 1966.281

707.16 1966.433 2.33 458.18 206.4755 258.721654 1966.433 567.203952 328.29 1966.433

680.61 1966.585 2.389 469.82 206.4914 262.5954833 1966.585 566.69424 317.82 1966.585

688.17 1966.737 2.38 468.08 206.5074 263.1552451 1966.737 566.184193 322.41 1966.737

694.60 1966.89 2.324 457.11 206.5234 254.0903742 1966.89 565.674481 321.76 1966.89

699.18 1967.042 2.27 446.52 206.5394 244.8478348 1967.042 565.165104 319.77 1967.042

693.95 1967.194 2.258 444.19 206.5554 241.0201862 1967.194 564.655057 316.17 1967.194

699.18 1967.346 2.253 443.24 206.5714 241.6044733 1967.346 564.14501 318.92 1967.346

690.09 1967.499 2.248 442.29 206.5873 238.015595 1967.499 563.635298 313.87 1967.499

689.45 1967.651 2.247 442.13 206.6033 237.6795761 1967.651 563.125921 313.79 1967.651

686.26 1967.803 2.241 440.98 206.6193 235.6010479 1967.803 562.616544 311.85 1967.803

677.51 1967.955 2.257 444.17 206.6353 236.1454261 1967.955 562.106497 308.51 1967.955

683.74 1968.107 2.287 450.11 206.6513 243.9966775 1968.107 561.59645 315.20 1968.107

707.83 1968.26 2.318 456.24 206.6672 257.164601 1968.26 561.086738 331.93 1968.26

731.52 1968.412 2.326 457.85 206.6832 265.2361697 1968.412 560.577361 344.82 1968.412

729.37 1968.564 2.295 451.79 206.6992 258.615582 1968.564 560.067649 340.82 1968.564

725.81 1968.716 2.267 446.31 206.7152 252.2057394 1968.716 559.557267 336.52 1968.716

699.18 1968.868 2.234 439.85 206.7312 238.3663402 1968.868 559.04789 320.68 1968.868

685.63 1969.021 2.244 441.85 206.7472 236.4054288 1969.021 558.538178 314.75 1969.021

705.82 1969.173 2.277 448.38 206.7631 248.8287603 1969.173 558.028801 328.98 1969.173

721.58 1969.325 2.306 454.13 206.7791 258.9487982 1969.325 557.518084 340.04 1969.325

720.18 1969.477 2.286 450.22 206.7951 254.6814409 1969.477 557.008707 337.60 1969.477



722.28 1969.629 2.254 443.95 206.8111 248.9972405 1969.629 556.49933 335.49 1969.629

696.56 1969.782 2.226 438.47 206.8271 236.3326437 1969.782 555.989618 320.67 1969.782

690.73 1969.934 2.211 435.55 206.843 231.7227232 1969.934 555.480241 316.60 1969.934

684.37 1970.086 2.214 436.18 206.859 230.4695202 1970.086 554.969524 313.89 1970.086

681.86 1970.238 2.24 441.33 206.875 234.8844876 1970.238 554.460147 315.27 1970.238

681.86 1970.39 2.256 444.52 206.891 238.0875919 1970.39 553.950435 317.10 1970.39

686.26 1970.543 2.263 445.93 206.907 240.8433221 1970.543 553.441058 320.57 1970.543

697.21 1970.695 2.269 447.15 206.923 245.2955649 1970.695 552.931011 327.33 1970.695

706.49 1970.847 2.275 448.37 206.9389 249.1794379 1970.847 552.421299 332.95 1970.847

728.65 1970.999 2.274 448.21 206.9549 255.0911649 1970.999 551.911922 343.37 1970.999

733.69 1971.151 2.271 447.65 206.9709 255.8750349 1971.151 551.401875 345.48 1971.151

756.85 1971.304 2.272 447.88 206.9869 261.9901997 1971.304 550.891829 354.98 1971.304

750.73 1971.456 2.268 447.13 207.0029 259.7366655 1971.456 550.382117 352.51 1971.456

711.22 1971.608 2.288 451.10 207.0188 253.3195617 1971.608 549.872739 338.30 1971.608

678.74 1971.76 2.345 462.38 207.0348 255.1464715 1971.76 549.363362 326.99 1971.76

720.18 1971.912 2.447 482.53 207.0508 287.2340871 1971.912 548.853985 360.59 1971.912

759.17 1972.065 2.49 491.04 207.0668 305.7955667 1972.065 548.343603 384.03 1972.065

780.70 1972.217 2.435 480.23 207.0828 300.1094901 1972.217 547.834226 385.85 1972.217

776.62 1972.369 2.349 463.31 207.0987 282.2524674 1972.369 547.325184 373.63 1972.369

688.17 1972.521 2.286 450.92 207.1147 246.6069672 1972.521 546.815807 328.60 1972.521

669.57 1972.673 2.287 451.15 207.1307 241.1804381 1972.673 546.30576 318.61 1972.673

688.17 1972.825 2.297 453.16 207.1466 248.8791339 1972.825 545.796383 330.43 1972.825

699.83 1972.977 2.3 453.78 207.1626 252.9265121 1972.977 545.287006 337.12 1972.977

707.83 1973.129 2.307 455.20 207.1786 256.6280875 1973.129 544.777629 342.13 1973.129

723.68 1973.282 2.306 455.04 207.1946 260.8310075 1973.282 544.267582 349.61 1973.282

715.33 1973.434 2.31 455.86 207.2105 259.4018635 1973.434 543.758205 346.64 1973.434

711.90 1973.586 2.313 456.49 207.2265 259.0992751 1973.586 543.249163 345.73 1973.586

709.86 1973.738 2.316 457.12 207.2425 259.1751047 1973.738 542.739786 345.44 1973.738

708.51 1973.89 2.312 456.36 207.2585 258.0584559 1973.89 542.230409 344.70 1973.89

707.83 1974.042 2.297 453.44 207.2745 254.9593668 1974.042 541.720027 343.09 1974.042

696.56 1974.195 2.288 451.70 207.2904 250.020092 1974.195 541.21065 337.05 1974.195

690.09 1974.347 2.288 451.73 207.3064 248.1809548 1974.347 540.701273 334.16 1974.347

691.37 1974.499 2.284 450.98 207.3224 247.8200986 1974.499 540.191896 334.76 1974.499

693.95 1974.651 2.28 450.22 207.3384 247.8370864 1974.651 539.681849 335.98 1974.651

700.49 1974.803 2.271 448.48 207.3543 247.9999697 1974.803 539.172806 338.52 1974.803

703.81 1974.955 2.266 447.52 207.3703 248.0076951 1974.955 538.663429 339.86 1974.955

713.27 1975.107 2.25 444.40 207.3863 247.5427279 1975.107 538.154052 342.60 1975.107

715.33 1975.26 2.255 445.42 207.4022 249.1470434 1975.26 537.644005 344.36 1975.26

711.90 1975.412 2.261 446.64 207.4182 249.4377247 1975.412 537.134628 343.89 1975.412

722.28 1975.564 2.266 447.66 207.4342 253.3087125 1975.564 536.625251 349.14 1975.564

724.39 1975.716 2.277 449.87 207.4502 256.0985113 1975.716 536.115874 351.60 1975.716



732.24 1975.868 2.291 452.67 207.4661 260.9921467 1975.868 535.606497 356.71 1975.868

759.94 1976.02 2.334 461.20 207.4821 276.52585 1976.02 535.096785 372.63 1976.02

770.18 1976.172 2.361 466.57 207.4981 284.3663421 1976.172 534.587408 379.94 1976.172

776.62 1976.324 2.352 464.83 207.5141 284.1484566 1976.324 534.078031 381.14 1976.324

781.52 1976.476 2.314 457.36 207.53 277.8207681 1976.476 533.568654 377.85 1976.476

749.22 1976.629 2.29 452.65 207.546 265.3867577 1976.629 533.058272 364.37 1976.629

743.97 1976.781 2.29 452.68 207.562 264.1152245 1976.781 532.54923 362.78 1976.781

729.37 1976.933 2.291 452.92 207.578 260.587899 1976.933 532.039853 357.69 1976.933

721.58 1977.085 2.289 452.55 207.5939 258.1666154 1977.085 531.531145 354.64 1977.085

715.33 1977.237 2.28 450.81 207.6099 254.7390447 1977.237 531.021098 351.32 1977.237

706.49 1977.389 2.272 449.26 207.6259 250.754394 1977.389 530.511721 346.95 1977.389

704.48 1977.541 2.265 447.91 207.6418 248.8543679 1977.541 530.003014 345.60 1977.541

692.66 1977.693 2.259 446.76 207.6578 244.3220048 1977.693 529.493972 339.95 1977.693

696.56 1977.845 2.253 445.61 207.6737 244.3176798 1977.845 528.984595 341.40 1977.845

695.25 1977.997 2.255 446.04 207.6897 244.3863085 1977.997 528.474883 341.36 1977.997

690.73 1978.149 2.252 445.48 207.7057 242.522858 1978.149 527.965841 339.30 1978.149

693.31 1978.302 2.257 446.50 207.7217 244.3168733 1978.302 527.456463 341.36 1978.302

690.09 1978.454 2.252 445.55 207.7376 242.4350847 1978.454 526.947421 339.67 1978.454

690.73 1978.606 2.255 446.18 207.7536 243.2676959 1978.606 526.437709 340.62 1978.606

683.74 1978.758 2.254 446.01 207.7696 241.0460972 1978.758 525.928332 337.59 1978.758

683.74 1978.91 2.255 446.24 207.7855 241.2945693 1978.91 525.41929 338.04 1978.91

686.26 1979.062 2.264 448.06 207.8015 243.8805023 1979.062 524.910248 340.55 1979.062

697.21 1979.214 2.332 461.55 207.8175 260.594626 1979.214 524.400871 353.59 1979.214

694.60 1979.366 2.424 479.80 207.8334 278.1022333 1979.366 523.891159 363.11 1979.366

697.21 1979.518 2.426 480.23 207.8494 279.3050667 1979.518 523.382117 365.01 1979.518

699.83 1979.67 2.336 462.45 207.8654 262.2947853 1979.67 522.872739 356.27 1979.67

695.25 1979.822 2.256 446.65 207.8813 245.1884355 1979.822 522.364032 345.38 1979.822

699.18 1979.974 2.259 447.28 207.8973 246.9635194 1979.974 521.853985 347.74 1979.974

701.15 1980.127 2.26 447.51 207.9133 247.7771286 1980.127 521.344608 349.01 1980.127

703.14 1980.278 2.258 447.15 207.9292 247.9965413 1980.278 520.835901 349.93 1980.278

701.82 1980.43 2.263 448.17 207.9452 248.6602223 1980.43 520.326859 350.27 1980.43

690.73 1980.583 2.266 448.80 207.9612 246.1023073 1980.583 519.816477 346.15 1980.583

697.86 1980.735 2.266 448.83 207.9771 248.224856 1980.735 519.30777 349.59 1980.735

696.56 1980.887 2.259 447.48 207.9931 246.512021 1980.887 518.798727 348.53 1980.887

702.48 1981.039 2.261 447.91 208.0091 248.6536535 1981.039 518.28935 351.56 1981.039

706.49 1981.191 2.269 449.53 208.025 251.4187976 1981.191 517.780308 354.46 1981.191

713.27 1981.343 2.285 452.74 208.041 256.5223074 1981.343 517.270596 359.41 1981.343

754.54 1981.495 2.367 469.02 208.057 283.5535604 1981.495 516.761219 385.19 1981.495

791.51 1981.647 2.491 493.63 208.0729 316.8374181 1981.647 516.252177 414.39 1981.647

796.60 1981.799 2.536 502.58 208.0889 326.9370591 1981.799 515.743135 422.66 1981.799

796.60 1981.951 2.419 479.43 208.1049 303.8008534 1981.951 515.233423 406.02 1981.951



Chart & Results:


Chart nr: 1 Velocity vs. depth:

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

400.00 500.00 600.00 700.00 800.00 900.00 1000.00

Deth

[m]

Velosity ,Vp[mic,sec/m]

Fig. C2: Velocity vs. depth.




Chart nr: 2

Pore pressure based on Vertical Method:

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

150 200 250 300 350

Dep

th[m

]

Pressure [kg/cm2]

Pressure calculation [Vertical Method]

Fig.C3: Pore pressure predication using vertical method.




Chart nr: 3

Pore pressure based on Horizontal Method:x


X=3

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

150.00 200.00 250.00 300.00 350.00 400.00 450.00

Dep

th[m

]

Pressure [kg/cm2]

PorePressure[Horizontal Method]

Fig. C4 : Pore pressure predication using Horizontal method.




Chart nr: 4

Pore pressure based on Horizontal Method:x


X=2

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

150.00 200.00 250.00 300.00 350.00 400.00

Dep

th[m

]

Pressure [kg/cm2]

PorePressure[Horizontal Method]

Fig. C5: Pore pressure predication using Horizontal method.



Appendix D

Estimation of pore pressure on over consolidated shale:

Well Name: 34 10-F-4 H : AFelt: Gulfaks

Well Name: 34 10-F-4 H : BFelt: Nor ne: N6608 10-E-3 H

BnormA5000V

B1

maxMax A

5000

BAovbpore ])5000V[(PP

)BU(

MaxBMaxAA

UBB

TABLES7: Well data & calculation:

A Gulfax: 34 10-F-4 H

B Norne N6608 10-E-3 H

Maxstress 6200

A 4.45

B 0.92

U 3.15

Felt A' B'

Norne 2.3 0,94

Gulfax 2.65 0,95



B A ft

DT(Norne) DT(Gulfax) DEPTH[ft]

117.4046 95.041 4920.079117.5041 94.687 4921.391117.6487 95.261 4922.703

117.7898 95.856 4924.015

117.8284 95.57 4925.327

117.7269 95.652 4926.639

117.5482 95.482 4927.951

117.3473 95.075 4929.263117.1681 93.625 4930.575

117.0302 93.372 4931.887

116.8764 92.496 4933.199116.6941 92.75 4934.511

116.5111 93.015 4935.823116.3445 93.564 4937.135116.2053 94.03 4938.447116.1282 94.693 4939.759

116.14 94.273 4941.071

116.2257 94.383 4942.383

116.3676 94.438 4943.695

116.5407 94.885 4945.007

116.714 94.395 4946.319

116.8771 93.54 4947.631

117.1356 93.217 4948.943117.5365 93.308 4950.255118.0558 93.122 4951.567

118.6244 93.5 4952.879119.147 93.822 4954.191

119.5855 94.367 4955.503120.0449 95.266 4956.815

120.5087 95.955 4958.127120.8572 96.167 4959.439120.8677 94.938 4960.751

120.185 95.328 4962.063

119.131 96.971 4963.375118.0887 98.426 4964.687117.2851 98.398 4965.999116.8237 99.308 4967.311

116.653 98.638 4968.623116.5115 98.28 4969.935116.3469 95.531 4971.247

116.2236 93.617 4972.559



116.1818 85.337 4973.871116.219 85.411 4975.183

116.2871 74.53 4976.495

116.3207 76.924 4977.807116.3203 75.492 4979.119116.3057 77.122 4980.431116.3113 78.689 4981.743

116.3901 77.623 4983.055116.5629 74.991 4984.367116.7513 76.283 4985.679

116.898 75.472 4986.991

116.9703 76.492 4988.303116.9717 76.84 4989.615117.0152 76.506 4990.927117.2242 74.954 4992.239

117.5478 71.1 4993.551117.881 71.101 4994.863

118.1049 72.611 4996.175118.114 73.352 4997.487

117.8998 68.438 4998.799117.6524 64.551 5000.111117.4475 60.674 5001.423117.3019 67.651 5002.735

117.1866 71.042 5004.047117.0413 74.085 5005.359116.8531 75.103 5006.671116.6733 74.705 5007.983

116.5405 68.055 5009.295116.4731 68.36 5010.607116.4606 68.501 5011.919116.4402 70.411 5013.231

116.387 71.745 5014.543116.3515 73.003 5015.855116.3938 74.508 5017.167

116.568 75.822 5018.479

116.9096 77.122 5019.791117.3016 76.909 5021.103117.6277 76.848 5022.415117.8483 77.32 5023.727

117.9491 79.599 5025.039117.9364 117.5365 5026.351

117.811 118.0558 5027.663117.6017 118.6244 5028.975



Chart Nr:

Fig. D1: sonic travel time vs. depth.



Fig. D2: Velocity and Normal compaction Curve.



TABLE 8: Pore Pressure on overcosolidated Shale:

Well Nr: A B

TVD[m] Ppore[SG] Ppore[SG]

764.295 0.82 0.812

767.34 0.82 0.82782.565 0.83 0.82843.465 0.83 0.82

846.51 0.83 0.83

1368.728 0.834 0.831738.391 1.25 1.21828.218 0.8 0.8

1958.24 1.26 1.06

1978.032 1.15 1.052058.116 0.81 0.832098.005 0.81 0.832237.771 0.81 0.83

2377.841 0.824 0.8322437.827 0.824 0.834

2477.717 0.824 0.834



Fig. D3: Pore pressure predication using Eaton Method.



Fig.D4: Pore pressure predication using Bower’s method.



Fig.D5: Pore pressure predication using overcosolidated model.



APPENDIX E:Nomenclature:

A & B: Curve fitting constant for normal compacted shaleobsA : Observed attribute

normA : Normal attribute a : Formation factor constant

a : Lithology constant a : The intercept

b : Slop

cC : Average Constant Compression index D : density D : Depth of insert [ft]De : depth where the vertical line crosses the compaction line.

DST : Drill Stem Test e : Void ratio

ie : Void ratio corresponded to v =1 psiE : young’s Modulus

FGP : Formation pressure gradient (mud density equivalent)

.hydGP : Normal (hydrostatic) pressure gradient (mud density equivalent)

K : Porosity decline constant K : constant LWD : Logging While Drilling

MESPOSH: Measure Pressure on Shale (direct measurement) M : (1.85=Geometrical factor by Perez-Rosales) M : Geometrical factor m : Cementation factor m : Lithology constantNCC: Normal Compaction Curve

(MN ): Ratio of measured value (i.e. velocity, resistivity or acoustic travel time) to the

expected value at normal trend line at the same depth.

pP : Pores pressureP e : overburden pressure where the vertical line crosses the compaction line.P pore : Shale pressure [psi]

wR : Resistivity of the fluid saturating the rock

wR : Resistivity of bound water

oR : Resistivity of the system



ShR : Resistivity of ShaleRt : Formation resistivitySWD : Seismic While DrillingSw : Water saturation T : Temperature ( o F)U: Unloading curve parameter (U= 3.13, For Golf Cost, Bower 1995)V: Sonic velocity [ft/sec]

VSP-WD : Vertical Seismic Profiling While DrillingWBM : Water Based Mud

=D

v : Vertical stress gradient [ ]ft

psi

β : Constant =297.6 : Porosity of shale @ depth D

i : Initial shale porosity @ surfaceΦ r : Residual PorosityΦ r : (0.1 =satisfactory for sand)

obtot,Z : Total stress or Overburden

v : Effective stress

norm : Effective stress

Max : Max effective stress corresponds to Max

Max : Max. Effective stress [SG]

v : Vertical stress

ovb : overburden stress

Δt : Formation transit travel time ([fts

] or [ms

])

Δt m :Matrix transit travel time

Δt fl : Fluid transit travel time

at : Abnormal transit time [ftsec ]

nt : Normal transit time [ftsec ]

relT : Relative Time Difference

dsT : Travel Time across the Drill-String

fT : Travel Time across the FormationƲp : formation velocity

Ʋm : Matrix velocityƲfl : fluid velocity

Max : Sonic velocity which is the onset point of the unloading [ft/sec]

pressure measurement in shale

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