Options available from the Vel results screen include: <Fl> NewMethod - for returning to the Vel selection menu, <F2> Equation -for computing a single value and viewing the equation for a method,<F8> Print Table - for printing the results table, <F4> Selection -for selecting the clay volume to use in the analysis when more thanone clay volume method was computed, <F5> Print Scrn - for printingthe screen, <F9> Notes - for viewing notes compiled by Dr. Asquithrelevant to a calculation or crossplot, and <FIO> Main Menu - forreturning to the Pass 1 Menu.

Notes available for Vel calculations are shown below.

Cia!:! Detenllnat.lon rkJt.es:

1. GaIIIIaJIa!l IInrellable 1Ihef1:- Jladloact.lue ••1Je'als mher ~n clCJ9Spresent.

Z. 51' IInreliable uhen:- JW tal approaches 1.9- ZoIE Is \hln «18')- Gas :alii! Is IJ)drocarbon hear IIl!J

Press <Fl> rkJt.es IIem or <F1B> too ront. iroe

Note: by selecting <FIO>, the program continues, and by selecting<FI>, the notes menu is presented and notes pertaining to other por-tions of the program can be viewed.

Page 18

DQt9rming LithologyCBA provides several crossp1ots to estimate lithology. After

selecting option 2, Lithology Determination, from the Pass 1 Menu,the list of lithology crossplots is displayed. These crossplots in-clude: Density-Neutron, Neutron-Sonic, Density-Sonic, MID, M-N, andLithoDensity (PE). The MID plot and M-N plot use the density,neutron, and sonic logs. The LithoDensity crossplot utilizes thephoto electric curve of the lithodensity curve.

1. DensI~1.ron

Z. lleuvan-Sonlc

3. Denslw--Sonlc

1. nlD

S. !HI

r.. LlUnDenslty (PEl

7.~

Af~er a lithology c:ossplot method is selected, CBA prompts forneeded lnputs and then dlsplays the crossplot along with a graph ofthe clay volume. Below is an example of a Density-Neutroncrossp1ot.

UolI 1113

••

10

to

,.

.,..,. ..

fIItI

rl> Pick Lith (F'Z> (;&10 Pur <r.s> Prt So", (F1I> Hi (n> /totu <nil) lI.turn

Page 19

Options from the crossplots screen include: <Fl> Pick Lith -for selecting the lithology for the analysis, <F2> Calc Par - forcomputing porosity, <F5> Prt Scr - for printing the screen, <F8> Hi- for highlighting points on the crossplot in a depth range, <F9>Notes - for viewing technical notes about the crossplot, and <FIO>Return - for returning to the Pass 1 Menu. When picking lithology«Fl» the user can select a single, dual, or tri-lithology system.Options are SS (sandstone), LS (limestone), DO (dolomite), SS-LS,SS-DO, LS-DO, DO-AN, SS-LS-DO, LS-DO-AN, and SS-LS-Sa. (Note: ANstands for Anhydrite and Sa stands for salt.)

Computing PorosityPorosity can be calculated from this screen or from the

Porosity Calculation Option in the Pass 1 Menu. A lithology must beselected prior to computing porosity. The porosity calculationscreen gives a table of depth and porosity values and two graphs.One graph shows the different volumes of lithology (sandstoneshaded yellow, limestone blue, dolomite purple, and anhydrite red)and the other gives porosity.

PwU. ---------- "'Dn -~~~I Sel ••• , •• 1101 ••.•,- is Vel-SF ~

Po ••

F4 •.••j"t TaLl.n ItDtuF5 Print $crnr18 tuin *'nu

Porosity can be computed from the density-neutron logs,neu~ron-sonic logs, density-sonic logs, density log, neutron log,sonlC log, resistivity curves, microlog/minilog, and from lab datatransforms.

Page 20

Checking RxoThe last option from the Pass 1 Menu is Option 4, Check Rxo'

This option provides users the ability to compute Rz, resistivity ofthe mixed zone when an Rxq device is not available. The userselects Rxo/~f or Rs1/Rz ~n calculations and crossplots. The useris prompted for inputs and ~f or Rz is computed and displayed.

Ibte: rkl Jtxo daw extsts for \hIs dawset. Tle analysis can ron1ihue uslll!JIs 1I1tz (I ns$ead~ 1b:IY1W) whereJtz IsaJIIfU1ed fnll! \he ro 1I0111ll!J fllnlUla:

1Jtz =

2 1 - 2- + --..., JW

2 = 8.1li high peneablllt!J2 = 8.1r.'5 III!dIIlf'lpeneablll~2 = 8.1 1011 peneablll~ and/or

sha 11011 Inuas Ion

Ha a~ I!e!I ~ contlme

Tsurf:W II n.n:1Irr:Iota I Depth:Auerage FlrIIiltloo J)epUI: I:·:·11-'

"res,; (flH> to cont lillie

Page 21

Tsurl:JW" 8 n .n:lilt:lata I Depth:Allerage FIrftil~iOll Depth:

?9.87175175<JOO4<JOO4.5

Jkj: •JW: '1.:· .2:

2 = 9.1li high perMabllity2 = 9.975 lied lUll perMab III i!J2 = 9.1 1011 peneab III i!J and/or

shaiiOll lnuaslllll

Pres- <FIll' to r:olltilllOP

rsurr: ?9JW II n: .87T1: 175an: 175rata I Deyth: <JOO4Allerage rlrftil~ lOll Iepth: <JOO4.5.,: .9J4JW': .919'J?42: .975

2 = 8.1fi high pemeabllli!J2 = 9.975 lied lUll )Ie!W!>iIbIII ~2 = 9.1 lOll peneab III i!J and/or

sha 11011 Inuas Ion

R2 = 8.:Hi'.l oIIHI

Pr..,,,,, <nu· tu LUlltllll't!

Page 22

V. Estimating Pore Type and ProducibilityPass 2 - Pore Type, and Producibility is option 4 from CBA's

Main Menu. The Pass 2 Menu is shown below.

/w;~ z ~ rom: n'rI: ANIl /'!lODUe /111/./ J'.' "[1'111

1. Ptn! ~ Crossp lots

Z. Pore T!;IPe Review

3. II: Pmen1.la I Crossp lots

4. II: Pmen1.lal Jeuleu

5. IIeiurn ~ "" In nero

U'.e 1 dud £ tl,f'lI [NUll tu !.e)t!ct ~II UptlOll <

From Pass 2, the user can view pore type crossplots, displaythe pore type review screen, view hydrocarbon potential crossplots,display the hydrocarbon potential review screen, and return to themain menu.

When core data is not available to compute m, pore type modelscan be used. The pore type can be estimated from log data. CBAprovides several crossplots which help the analyst determine poretype: Archie's water saturation vs. Ratio Water saturation, SonicPorosity vs. Total Porosity, Porosity computed using the Short Resis-tivity reading vs. Porosity using the True Resistivity values, M-N,and Dew Plot.

1. !Wa-!M-

2, oIs - oOt

3. 116 - fO\

4. " -"

S. lieu Plo1.

r.. IIetunJ

Page 23

After selecting a particular crossplot, CBA prompts the userfor any needed inputs, then displays the crossplot and depth graphsof clay volume and porosity. Each crossplot has shaded regions forthe different pore types: intercrystaline/intergrannular-green,vuggy-brown, bimodal-red, or fracture-purple. Shale points aregraphed as blue and matrix as yellow on the crossplots.

lie I., J._Per

411 "

s•••.• 0

.0 : : ;

··r··!:···!";

(ra) Hi (F9) HDt.,. (1"111) Iirt" •.••

Options available from the Pore Type Crossplot Screen include<F5> Prt Scrn - to print the screen with the graph, <F8> Hi - tohighlight data in red on the crossplot, <F9> Notes - to read notesabout the crossplot, and <FIO> Return - to return to the Pass 2Menu.

Each of the pore type crossplots givesabout the pore type for a particular depth.screen, Option 2 from the Pass 2 menu helpsdominate pore type for each depth.

different informationThe pore type review

the user determine the

- - --- - --- - --<~) Print: Core-e-n <r1a) Jitetu •••.•

Page 24

The pore type review screen graphs lithology volumes on theleft and porosity on the right. In between, for each depth, thepore type column is shaded when that depth falls within the poretype region on the crossplot. CBA uses a set of rules to determinethe dominant pore type for each depth. The suggested pore type isgraphed in the Pore Type Summary column. The user can overridethese suggested pore types by selecting <F2> Edit. The user thendefines the desired pore type by clicking that column with themouse. The user can increase or decrease the interval by moving themouse to the depth on the Pore Type Summary column and clicking. Toreturn the Pore Type Summary to the types originally selected byCBA, choose <Fl> Defaults. The screen can be printed from <F5>,Print Screen, and the program can be returned to the Pass 2 Menufrom <FIO>, Return.

Crossplots are invaluable in aiding analysts to determine if azone will be hydrocarbon bearing. To view these crossplots selectOption 3, HC Potential Crossplots, from the Pass 2 Menu.

The crossplots available include: Neutron Porosity vs. DensityPorosity, Archie Water Saturation vs. Ratio Water Saturation, DewPlot (Rs/Rz vSo ~/~), BVW (Bulk Volume Water, Swa vs. $t), MovedHydrocarbon (~Rd vs. ~Rs)' PRI (Production Index Plot), and $ept vs.$t. In these crossplots, the water region is shaded blue. Again,the procedure is to select a crossplot to view, enter data requiredat the prompts, then view the crossplot. Beside the crossplot,graphs are given of clay volume and porosity. The options from thecrossplots screen are <F5> Prt Scrn, <F8> Hi, <F9> Notes, and <FlU>Return. Below is an example of a Swa-Swr crossplot.

Vel "1'NC c.ouplot II 111II 411 II

s- ..•_ IIUO

.00

o. ·....• 0 ..'\0 .

.·10 .Iw . .a .

00 :"·.." ,. ,- .•• - I·

it 11II0

nu: (F15) I'Pt I•••• (fa) Hi (f'J) Motu <HII) Return

Page 25

The results of the hydrocarbon crossplots can be summarized inthe HC Potential Review screen available from Option 4, He PotentialReview, in the Pass 2 Main Menu.

48 Po•. a

• Plot IncUeator.1 1'01 JIIn t; •••.2 " ••.•.~Ia" w.t.3 D.•• w.t• 5 No" •• He w.t.' PIli w.t.7",pt tot w.t

The review screen is designed so that users can quickly lookover depth ranges to view where data is plotted in the hydrocarbonpotential portion of the crossplots (not shaded in the wet region)On the left side of the screen, lithology is graphed and on theright, porosity. Each crossplot is given a column with a key forthe corresponding number displayed. The first column plots red forthe neutron-density crossover. Options for this screen include <F5>Print Screen and <FIO> Return.

Once the pore type is determined, or core data is available, mand n can be determined from Pass 3 (Option 5 of CBA'a Main Menu).In Pass 3, m can be calculated from pore type models, m and n can bedetermined from core data, and n can be computed using relative per-meability curves or capillary pressure data.

Z. Call1lla\e " and " fl'Oll Core Data

3. CaJ01Ja~ " uslJV s...lrr

4. IIetunI to na 1n I'!m

Page 26

To use one of the pore models, select Option 1, Calculate Mfrom Pore Type. From the screen displayed, the user selects whichmodel to use for each pore type represented in the data.

c:a-.:. ••••••• t ••..•:

A graph of the pore types at each depth is displayed along witha table listing all the models available: Nugent Method (Vuggy),Nugent Method (Oomoldic Only), Low Porosity M (InterX/Fracture),Focke and Munn (Vuggy), Rasmus (Fracture), W Technique (Bimodal),m-Phi Transform, and constant m. The program takes the first poretype and highlights with an arrow a recommended model. The userselects the model desired by typing in the number corresponding tothe model. Each pore type may have a different pore model. Optionsavailable include <FI> Edit to select different pore models and<FIO> Continue to return to the Pass 3 Menu.

_,hiD.:

~::::lt~ ~6::;;~"II-.o'-)

When core data is used to determine m and n, select Option 2,Calculate M and N from Core Data, from the Pass 3 Menu. The screenshows a graph of Fr vs. ~ and I vs. Sw. A m-~ transform is createdand can be used.

Po ••• T., •• :

10··••"'r:::~

,...1) Edi t: "'thotls (F1.8) ConUnu.

...•• =

Page 27

..c••

..,

r•....

to~

<nil) a.tura

f '11 or relatl've permeability curves are avail-I capl ary pressure ••able, Swirr can be used to compute n from Option 3, Calculate nusing Swirr, from the Pass 3 Menu.

f d II 1I1,1t.e N 115ill~ Suirr

CondI1.!ons fir calcula1.!lU n:1. Wa1.er-Free Produc1.!on Creserw!r a1. ~irr)

2. ~!lT auallable flU! caplll~ pressure orre la1.11e peI1Ieabll i~ curves

3. n a lread!:l detent! ned

frtlutldte I'Il1sill~ Suirr

Depth ~llTJ frac

The n values can only be computed if the following are true:production is water free (or water saturation is at irreduciblewater saturation), Irreducible water saturation is known from capil-lary pressure or relative permeability curves, and m has alreadybeen computed. The screen requests values for depth and Swirr. Atable of reservoir values including depth, irreducible water satura-tion, true resistivity, porosity, and m are entered. The value n isthen computed.

Page 28

VI. Performinq the Final Analysis - Computing Water Saturation andNet Pay

From Pass 1, 2, and 3, all the values needed to compute watersaturation have been determined. Selecting Pass 4, Final Analysis,from CBA's Main Menu takes the user to an input review screen tocheck values which will be used to compute water saturation.

Press <flll / tu milt lillie

a: 111- llatr Ix DensIty. g/a: _.w.Fluid Density. g/a: -n: • llatrlx Irauel Tille: arlll

.,. oiwHt: M'*I. fluid Irauel Tille: -'*'" IIiltrlx .R. Sm: _'m-

fto1,e: ~ Irchle COIPU~ using a=l. ,,=2. n=2

Page 29

Continuing from the input screen, CBA computes m and watersaturation and presents a table and graph of results. The tablepresents the values of Archie's water saturation, m, CarbonateMethod (Archie's equation with variable m), and the Ratio Method.The water saturation methods also are graphed. Options on thisscreen include <F3> Select Sw - for choosing the water saturationmethod to use in the net pay calculation, <F4> Net Pay - for comput-ing net pay thickness and graphing a summary of the analysis, <F5>Print Scrn - for printing the screen, <F6> Filter Sw - for changingthe display of Sw values over a certain value, <F8> Print Table -for printing the water saturation table, <F9> Notes - for viewingthe notes about water saturation, and <F10> Main Menu - for return-ing to the Main Menu.

_""hi • Sw-CaJob s.•...Ratio

~p ~~I Vel MothD4is Vel-SF s-..r"

When selecting the water saturation method <F3>, a small arrowappears below the Sw graph which can be moved by the up and down ar-row keys. The method indicated by the arrow is the one which willbe used in the net pay calculation. When selecting <F4> Net Pay,net paY,cut offs are requested for clay volume, porosity, and watersaturatlon.

Page 30

Sw (B~ Off J X: .*11.1111••

Uc:l (Bt Off. z: ••~_

I'Ir (B~Off. x: .-0.••

I'rl'S~ <fill' to continue

The net pay screen provides a summary of the analysis. Thefirst track presents clay volume, the second porosity shading effec-tive porosity, the third water saturation shading hydrocarbons, thefourth a summary including volume lithologies, porosity, and satura-tions, and the last track the neutron-density crossover. Screen op-tions include <FS> Prt Scrn, <F7> Report, <F8> Change Parameters,and <FlO> Return. The Change Parameters Option allows the user toenter the net pay cut off values. Return sends the user to thewater saturation calculation screen. The report can be printed,saved in a file, or displayed on the screen. After selecting <F7>Report, CBA requests information about the report including whetherto print it, save the report to a file, or display it, whether toinclude the header information, whether to include the parameter in-formation (constants used in the analysis), whether to include thenet pay results, the range of depths to include in the report, andwhether to include all depths or only those depths satisfying thenet pay criteria.

Page 31

Prim JIepon ~: 8$'RUOIM

Print Depth Ra1llE!: -*1;. To -@lR.

Prlni All Depths or Ite\ pay ~ Only7 Willln'weN

fa Is TOXLEDPf'P<;~ <FIll> to rnnt, iIlUP

Page 32