drilling engineering lecture 2

7/22/2019 drilling engineering lecture 2

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Fundamentals of DrillingEngineering & Rotary Drilling

Process

Kanad Kulkarni

04 10 2013


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Formation PressuresKnowledge of formation pressures is vital to the safeplanning of a well. Accurate values of formationpressures are used to design safe mud weights to

overcome fracturing the formation and prevent wellkicks. The process of designing and selection of casingweights/grades is predominately dependent on theutilization of accurate values of formation pressure.Cementing design, kick control, selection of wellheadand Xmas trees and even therig rating are dependent on the formation pressuresencountered in the well.


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Hydrostatic pressure is defined as the pressureexerted by a column of fluid. The pressure isa function of the average fluid density and thevertical height or depth of the fluid column.Mathematically, hydrostatic pressure is expressed as:

HP = g x f x Dwhere:HP = hydrostatic pressureg = gravitational acceleration f = average fluid density

D = true vertical depth or height of the column


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In field operations, the fluid density is usuallyexpressed in pounds per gallon (ppg), psi perfoot, pounds per cubic foot (ppf) or as specific gravity(SG).In the Imperial system of units, when fluid density is

expressed in ppg (pounds/gallon) anddepth in feet, the hydrostatic pressure is expressedin psi (lb/in2):HP (psi) = 0.052 x f (ppg) x D (ft)


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For the purposes of interpretation, all wellborepressures, such as formation pressure,fracture pressure, fluid density and overburdenpressure, are measured in terms of hydrostatic pressure.When planning or drilling a well it is often moreconvenient to refer to hydrostatic pressuresin terms of a pressure gradient. A pressuregradient is the rate of increase in pressure perunit vertical depth i.e., psi per foot (psi/ft). Itshould be noted that fluid densities, measured inppg or SG, are also gradients.


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Hydrostatic pressures can easily be converted toequivalent mud weights and pressure gradients.

Hydrostatic pressure gradient is given by:HG = HP / D (psi/ft)


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Calculate the hydrostatic pressure for the followingwells:a. mud weight = 9 ppg, hole depth = 10100 ft MD

(measured depth), 9900 ft TVD (trueverticaldepth)

Solution:

HP (psi) = 0.052 x f (ppg) x D (ft) = 0.052 x 9 x

9900 = 4632 psi


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b. mud gradient = 0.468 psi / ft, hole depth =10100 ft MD (measured depth), 9900 ft TVD(true vertical depth)Solution

= 0.468 (psi /ft) x 9900(ft) = 4633 psi


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Overburden PressureThe overburden pressure is defined as thepressure exerted by the total weight of overlying

formations above the point of interest. The totalweight is the combined weight of both theformation solids (rock matrix) and formationfluids in the pore space. The density of the

combined weight is referred to as the bulkdensity ( b).


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The overburden pressure can therefore beexpressed as the hydrostatic pressure exerted byall materials overlying the depth of interest:

ov = 0.052 x b x D

where ov = overburden pressure (psi) b = formation bulk density (ppg)D = true vertical depth (ft)


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And similarly as a gradient (EMW) in ppg:

ov= 0.433x b/0.052

Where, ovg = overburden gradient, ppg b = formation bulk density (gm/cc)(the factor 0.433 converts bulk density from gm/cc to psi/ft)


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A useful equation for calculating theoverburden gradient under field conditions of varying lithological and pore fluid density isgiven by:

ovg= 0.433[(1 ) ma + ( x f)]

where ovg= overburden gradient, psi/ft

= porosity expressed as a fraction f = formation fluid density, gm/cc ma = matrix density, gm/cc


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Rotary Drilling Rotary drilling is a method used to drill deep

boreholes in rock forma7ons of the Earth

s crust.

The method was ini7ally used to drill water wellsusing fresh water as the circula7on uid. Today, this

method is the only rock drilling technique used todrill deep boreholes (greater than 3000 B, or 900 mand up to 20, 000 B, or 6000 m)


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E Drilling was performed bymoving the drillstring upand down in reciprocatingmanner

was applicable for thewell of depth less than100 ft; and

production rate was aslow as 50 bbl/day

E Current rotary drillingcould drill more than30000 (about 10 Km);

E Could drill vertically,directional, fish-bone etc.

Derrickmans platform

Cable

Mud hoseSwivelKelly

Rotary table

Engines & generatorsMud pit

Mud pumpPipe ramp

Stacked drillpipe

Blowout preventer Casing

Cement

Drill bit

Drilling Rig


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Rotary Drilling Bit


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Tricon Drilling Bit


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The Three Necessary Components for Rotary Drilling


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Rotary Drilling Rig Classica?on


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Typical Drilling Rig Organiza?ons


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Steps to Drill A Gas/Oil Well1. Complete or obtain seismic, log, scou7nginforma7on or other data.

2. Lease the land or obtain concession.3. Calculate reserves or es7mate from best

data available.

4. If reserve es7mates show payout, proceedwith well.

5 . Obta in permits f rom conserva7on/

na7onal authority .


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Steps to Drill a Well - contd6. Prepare drilling and comple7on program.

.

Ask for bids on footage, day work, orcombina7on from selected drillingcontractors based on drilling program.

8. If necessary, modify program to t selectedcontractor equipment.


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Steps to Drill a Well - contd9. Construct road, loca7on/pla orms and other

marine equipment necessary for access tosite.

10. Gather all personnel concerned formee7ng prior to commencing drilling (pre-

spud mee7ng)11. If necessary, further modify program.12. Drill well.


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Steps to Drill a Well - contd13. Move off contractor if workover unit is

to complete the well.

14. Complete well.15. Install surface facili7es.16. Analysis of opera7ons with concerned

personnel.


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A Typical Onshore Drilling Rig


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Basic Drilling Equipment Power system Hois7ng system Fluid circula7ng system Rotary system

Well control system Well monitoring system


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Rig Power System Most of the power the hois7ng and uid

circula7ng systems (the same engines can

power both) Total power requirements for most rigs are

from 1000 hp and 3000 hp

The power of rotary rigs is generally generatedby diesel or gas-driven engines. The power istransmi^ed to the various rig systems by means

of mechanical or electrical drives


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Power System PerformanceCharacteris?cs Output horse power Torque Fuel consump7on for various engine speeds The shaB power,P , developed by an engine

is obtained from the angular velocity of theshaB, , and the output torque T


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Power System PerformanceCharacteris?cs The overall power efficiency determines the

rate of fuel consump7on, w f , at a given speed. The hea7ng value of a fuel for internalcombus7on is H

The input power is expressed in terms ofw fand H:


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TABLE 1 - HEATING VALUE OF VARIOUS FUELS

FuelType

Density(lbm/gal)

Heating Value(Btu/lbm)

diesel

gasolinebutane

methane

7.2

6.64.7---

19,000

20,00021,00024,000


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Engine power output

P = F . V

Power = Force * Velocity

Power = Ang.Vel. * Torque


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Power System PerformanceCharacteris?cs The overall efficiency of power-genera7ng

systems may be dened as the energyoutput per energy input:

Efficiency = (Power Out / Power in)


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Example 1 . A diesel engine gives an outputtorque of 1,740 ft-lbf at an engine speed of 1,200rpm. If the fuel consumption rate was 31.5 gal/hr,what is the output power and overall efficiency of

the engine?Solution: The angular velocity, , is given by

= 2 (1,200) = 7,539.8 rad/min.

The power output can be computed using Eq.1

( ) hp5.397/hplbf/min-ft33,000lbf/min-ft(1,740)7,539.8

TP ===


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Since the fuel type is diesel, the density is 7.2lbm/gal and the heating value H is 19,000 Btu/lbm (Table 1). Thus, the fuel consumption rate w f is:

w f = 3.78 lbm/min.

The total heat energy consumed by the engine isgiven by Eq. 2:

=

minutes60hour 1 lbm/gal)(7.2gal/hr 31.5 w f


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Q i = w f H

Thus, the overall efficiency of the engine at 1,200RPM given by Eq. 3 is

( ) ( )

lbf/min/hp-ft33,000

lbf/Btu-ft779lbm19,000Btu/lbm/min3.78=

iQ

Efficiency = (Power Out / Power in)

23.4%or 0.2341695.4

397.5===

it Q

P E


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Hois?ng System The func7on of the hois7ng system is to

provide a means of lowering and raising

drilling strings, case strings and othersubsurface equipment into or out of thehole

The principal components of the hois7ngsystem are the (1) the derrick andsubstructure, (2) the block and the tackle,

and (3) the drawwork


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Hois?ng system


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Hois?ng System Two rou7ne drilling opera7ons performed withthe hois7ng system:

Making a connec5on refers to the periodicprocess of adding a new joint of drillpipe athe hole deepens

Making a trip refers to the process of remove

the drilling string from the whole to change apor7on of the downhole assembly andthenlowering the drillingstring back to the hole

bo^om


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Making a connec?on


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Pulling out of the Hole


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Making a mouse hole connection


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Making a mouse hole connection - contd

SingleAdded.Ready toDrill

Moving Kellyto Single inMousehole

Stabbingthe Pipe


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UseElevatorsfortripping

Making a trip

Put Kelly inRathole

Why

trip?


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Making a trip - contd

Trippingone standat a time

60-90 ft


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Derrick or Portable Mast The func7on of the derrick is to provide the

ver7cal height required to raise sec7ons of

pipe from or lower them into the hole The greater the height, the longer the sec7on

of pipe that can be handled and thus the faster

a long string of pipe can be inserted in orremoved from the hole. The most commonly used drillpipe is between

2 and 30 B long


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Block and Tackle The crown bock

The traveling block The drilling line The principal func7on of the block and tackle

is to provide a mechanical advantage, whichpermits easier handling of large loads


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Drawworks The drawworks provide the hois7ng and braking

power required to raise and lower the heavystrings of pipe.

The principla parts of the drawworks are (1) thedrum, (2) the brakes, (3) the transmission, and(4) the catheads.

The drum transmits the torque required fprhois7ng or braking and it also stores the drillingline required to move the traveling block and thelength of Derrick


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Criteria for determining depth

limitation

Derrick Drawworks

Mud Pumps Drillstring Mud System Blowout Preventer

Power Plant

1 m = 3.28084 ft

1 ft = 0.03048 m


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Learning Outcomes Understand the rotary drilling processes

and the rigs Understand the equipment of rotary

drilling rig and the func7ons

Understand the power system andrelevant calcula7ons


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Drawworks


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Crown Block


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Crown Block


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Travelling Block


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Deadline Anchor


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Supply Reel


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Drilling Line


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Drilling Line


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Swivel


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Kelly


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Top Drive


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Kelly Bushing


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Master Bushing


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Rotary Table

drilling engineering lecture 2

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