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AVALON ™

NODAL ANALYSIS SYSTEM

USER’S GUIDE AND

REFERENCE

Version 2000.01

By

J a m e s L . B u c h w a lt e r , P h .D .

Gemini Solut ions, Inc.Houston, Texas

Un ited St at es of America

Ph one: (281) 759-4200



i

L im i t s o f l i ab i l i t y :

Gemini Solutions, Inc. reserves the right to revise its software and publications with no

obligation of Gemini Solutions, Inc. to notify any person or any organization of such revision.

In no event shall Gemini Solutions, Inc. be liable for any loss of profit or any other commercial

dam age, including but not limited to special, consequen tial, or oth er da ma ges.

Information in this document is subject to change without notice and does not represent a

comm itmen t on the pa rt of Gemini Solutions, Inc. The softwa re described in th is docum ent isfurn ished under a license agreemen t or nondisclosur e agreement . The may be used or copied

only in accordance with t he ter ms of th e agreement . It is against th e law to copy the softwar e

on an y medium except as specifically allowed in t he license or nondisclosur e agr eement .

Copyr ight N ot i ce:

©1996 Gemini Solutions, Inc. All right s reserved. This man ua l is protected by federal

copyright law. No par t of th is ma nu al may be copied or distr ibuted, tra nsm itted, tra nscribed,

stored in a retr ieval system or tr anslated into any h uma n or comput er language, in a ny form

or by any means, electr onic, mechanical, ma gnetic, man ua l, photogra phic, photocopy,

scanning, or otherwise, or disclosed to third parties without the express written permission of

Gemini Solutions, Inc.

T r a d e m a r k s :

AVALON is a tr adema rk of Gemini Solutions, Inc.



ii

Microsoft, MS, MS-DOS, Microsoft Excel, Visual Basic are trademarks of Microsoft

Corporation.



iii

P r i n t i n g :

1st Edition, 1rd PrintingPrint ed in th e United St ates of America.



iv



C o n t e n t s

5

C o n t e n t s

Limits of liability:______________________________________________________________ i

Copyright Notice: ______________________________________________________________ i

Trademarks: __________________________________________________________________ i

Acknowledgments ______________________________________________________________ 8

1___________________________________________________INTRODUCTION 9

1.1 - What Does AVALON Do ? ____________________________________________________ 9

1.2 - Setting Up _______________________________________________________________ 10

1.2.1 - Check the Hardware and System Requirements__________________________________ 10

1.3 _________________________________________________________________ Installation 10

1.4 ________________________________________________________ Uninstalling AVALON 12

1.5 ________________________________________ Using AVALON on Two or More Machines 12

1.6 ____________________________________________________________________ Backups 12

1.7 ___________________________________________________________________ Networks 12

1.8 - How To Use This Manual ___________________________________________________ 13

2___________________________________________________ USING AVALON 14

2.1 __________________________________________________________________ The Basics 14



C o n t e n t s

6

2.2 ________________________________________________ AVALON Menus and Commands 15

2.4 ____________________________________________________________Printing Graphics 16

2.5 - Exporting Pictures and Forms to Other Window Programs _______________________ 16

2.6 - Using Online Help_________________________________________________________ 17

2.6.1 - Help Contents __________________________________________________________ 17

2.6.2 - Help Index_____________________________________________________________ 17

3_____________________________________________ AVALON- THE BASICS 19

3.1 - Introduction______________________________________________________________ 19

3.2 – NODAL ANALYSIS DESIGN – the basics______________________________________ 20

3.3 – Creating a Report_________________________________________________________ 27

3.4 – Plots Available ___________________________________________________________ 29

3.4.1 – Gas reservoir with surface pressure fixed _____________________________________ 30

3.4.2 – Gas reservoir with bottom hole pressure fixed__________________________________ 313.4.3 – Oil reservoir with surface pressure fixed and reservoir curves ______________________ 32

3.4.4 – Tubing curves with sensitivities_____________________________________________ 33

4.1 - Introduction______________________________________________________________ 35

4.2 – Linking to a Merlin File ___________________________________________________ 35

4.2.1 – The basics_____________________________________________________________ 35

4.2.2 - Interactively Designing Surface Facilities _____________________________________ 36

4.3 – Using Merlin With Tubing Curves____________________________________________ 38

4.2.1 – History Matching Historical Well Flowing Pressure Data _________________________ 39

INDEX ___________________________________________________________2



C o n t e n t s

7



C o n t e n t s

8

Acknow l edgm en t s

In t he development and pr eparat ion of AVALON and this documentation, I have receivedsupport and constructive suggestions from more people than I could ever adequately

acknowledge. To th ese people we would like to express our sincerest appr eciation. Ther e are

th ose, however, who have assisted us to such an extent th at t hey must be acknowledged.

I would like to thank my father for imparting to me the humility to understand that for

everyth ing we know, there is far m ore tha t we do not know, as well as th e realization t hat only

by remar kable cha nce , have I been given th e opport un ities afforded to me in life.

I would also like to thank the women in my life - my wife, mother and sister for their

endless love, encour agement a nd support . In par ticular I would like to th an k my moth er for

keeping me along a st ra ight an d na rr ow line unt il I realized th at was th e proper line to follow,

and my beautiful wife for her hard work and countless personal sacrifices in the background

th at has h elped make Gemini Solutions a success.



C h a p t e r 1 : I n t r o d u c t i on

9

1I n t r o d u c t i o n

1.1 - Wha t Does AVA LO N Do ?

AVALON is an advanced, nodal

analysis program that can generate

nodal analysis curves for

determining the deliverability of oil

and gas wells under different

produced fluid and reservoir

compositions, for different well bore

and pipeline ar ran gements.

AVALON can be used as a stand

alone application where well bore

hydraulic and average reservoir

performance curves can determine

fluid deliverabilities at various

stages.

AVALON also brings some

unique abilities that are not contained in most nodal analysis packages. AVALON has atr an spar ent link t o the MERLIN simulator which allows horizont al flow lines to be int eractively

designed using t he well locat ions in ME RLIN. These nodal cur ves can th en be aut omatically

linked to various wells in the simulator, allowing Merlin to use the nodal curves to optimize



C h a p t e r 1: I n t r o d u c t i on

10

reservoir perform an ce with a ccuracies not possible in AVALON alone. For examp le the simp le

reser voir pr essur e drop equa tions us ed in AVALON’s r eservoir m odule calculations ar e

replaced by th e sophisticated reservoir model in MERLIN. With th is link AVALON has t he

ability to optim ize well tu bing designs not only on a n aver age well design basis, but on anindividua l well basis in a complicat ed reservoir with m an y heter ogeneities.

1.2 - S et t in g Up

1.2.1 - Check th e Har dwa re a nd System R equire men ts

Before you install AVALON, make sure that your computer meets the minimum

requirements and that your AVALON package contains the required items. The system

requirements include:

• Any IBM-compat ible machine with pentium processor or h igher.

• A 3 1/2" floppy dr ive.

• A CD ROM Drive

• Windows 95, 98, or Windows NT.

• Twenty m egabytes of free disk space for insta llation.

• Thirt y two megabytes of ra ndom a ccess mem ory (128 megabytes r ecommended).

• A mouse.

1.3 Ins ta l la t ion

To install AVALON perform th e following st eps:

1. I n s t a l l t h e H A S P : The HASP is a har d lock providing secur ity to th e GSI software

packa ges. It mu st be in place before an y GSI softwar e will work. Look on th e back of th e

compu ter a nd locate the par allel port. You may have your pr inter , a zip drive, or oth er

peripher al already plugged into it. If noth ing is cur ren tly connected to th e port , simply

plug the HASP directly into th e port . It does not need to be terminat ed.




11

If other periph era ls are cur ren tly connected, you ma y have severa l options. The HASP may

be inst alled an ywhere in th e chain of periphera ls. It ma y be inst alled directly int o th e

computer and then the other peripherals may be plugged into the HASP or it may be

insta lled furth er down the chain. For insta nce, if (as I do) you h ave a par allel zip drive andthen a pr inter plugged into th e zip, you m ay plug the zip directly into the print er an d th en

put t he HASP between th e zip and the prin ter. If you ha ve HASP’s for oth er pr ogra ms, you

ma y install them in an y order by plugging th em into each oth er.

2. I n s t a l l t h e d r i v e r s :

Follow th e instr uctions on t he inset of the inst allation CD or:

a) Select the folder named Avalon. It will normally be installed under

C:\ Gemini\ Pr ogram Files\ Merlin. Altern atively if Avalon has not yet beeninstalled select t he \ Drivers\ folder on th e CD.

b) Double click the Setdrivs.bat file

c) When you get a m essage indicat ing th at th e drivers were inst alled successfully you

will need to Reboo t the computer.

3. I n s t a l l t h e p r o g r a m s :

4. Close all other a pplicat ions ru nn ing in Windows. This includes program s such as MS Officewhich ma y load au tomat ically at st ar tu p. If you get the following err or dur ing start up, it

means you do have another program running that is interfering with the installation

process.

a) Insert Inst allation Disk into the CD Drive

b) Double click t he Set up.exe file to install t he pr ogram

c) Answer all questions.

d) Complete the driver installation described in step 2 and reboot the computer.

AVALON is now inst alled and a ctive and r eady to use.



C h a p t e r 1: I n t r o d u c t i on

12

1 .4 U n i n s t a l l i n g AVAL O N

Avalon inst alls in it’s own directory. To un insta ll, use th e install progra ms pr ocedur e

provided by Microsoft for Windows. To do th is select the Contr ol Pa nel option a nd t hen

Add/Remove Programs to uninstall Avalon.

1 .5 U s i ng AVALO N on Tw o or M ore M ach i n es

A single copy of AVALON may be used on only one ma chine at a time. If you h ave twomachines, perhaps a desktop at work and at home, or a desktop at work and a portable for

field work , you can inst all AVALON on both machines and then move the HASP between them

as needed.

1 .6 Backups

Backups may be ma de of th e installation disks. These disks may even be mainta ined on a

network t o allow mu ltiple users to always access the curr ent insta llation.

1.7 Networks

AVALON mu st be installed on th e machine on which it is to be used. It is not designed to

be a network program, though, if your system has the capability, you data sets may reside

anywhere.

It m ay be possible to obtain a t ru e network copy with mult iple users. It was n ot a vailable at

th e time of th is print ing. Please cont act GSI about t his option.




13

1.8 - How T o Use Th i s Man u al

The chapters in th is man ual a re organized to follow the work pa th you will use. In a ddition t he

sam ples directory un der t he AVALON inst allation folder cont ains several oil an d gas example

problems

I t i s s t rong ly r ecom m ended t ha t a l l u ser s tak e a bas ic Appren t i ce /Mer l in s chool t o

learn h ow to use the simulat ion a nd geostat istics software. This man ua l will not t each you h ow

to use t hese pr oducts - only how to use th e tools.



Ch ap ter 2 : Using Avalon

14

2Us in g AVALON

2.1 Th e Ba s ics

When you click the AVALON icon the last file that was opened will be read and appear on

th e home form.

Th e AVALON interface consists

of menu bars a nd toolbox. The menu

bar displays the commands that you

use to complete ma ny ta sks. This

chapter shows you some basics for

usin g AVALON.



Ch ap ter 2 : Using AVALON

15

2.2 A V A L O N M en u s a n d C om m a n d s

Choosing a command tells AVALON what to do

next – create a new file, open a Merlin file, and so on.

Comma nds t hat carr y out similar actions a re grouped

on a menu. For example, th e File menu cont ains

commands you use to open, save, and delete your

nodal files. The menus ar e listed on the menu bar a t

th e top of th e inter face window.

You use the mouse or the keyboard to display the

comm and s on each menu . To open the menus andbrowse through the commands, click the menu item

with th e mouse, or pr ess the ALT key, and t hen pr ess

the underlined letter in the name of the menu you

want to open.

For example, opening the File menu in Digitizing

tool displays these comm an ds.

Some commands are unavailable and appeardimmed on a menu until another selection is made.

AVALON carries out some commands right away.

If more information is needed to complete a command, AVALON displays a dialog box or

an other form. You select options in th e dialog box to contr ol how the comm an d is car ried out.

For calculat ion comman ds, AVALON displays a message askin g you to wait. No action should

be tak en u nt il the calculat ion is finished.

C h o o s in g Co m m a n d s




16

You can choose comm an ds from t he men us or pr ess th e shortcut key assigned to commonly

used comman ds. On the men us, the shortcut key is shown to th e right of th e comman ds. To

choose a comm an d from a m enu:

1 Point to a m enu n ame a nd click t he left mouse button for a r ight han ded mouse.

2 Point to a comm an d na me an d click th e left m ouse button.

-Or-

1 Press t he ALT key to activate the m enu bar .

2 Press the un derlined letter in th e menu nam e.

3 Press th e underlined letter in a comma nd na me.

If a command name is followed by an ellipsis (...), a dialog box appears so you can set the

options you wan t.

2 .4 Pr i n t i n g G raph i c s

Avalon contains a r eport option t o build a st an dar d report in a Rich Text form at . The Rich Text

format (RTF) can be imported directly into most word processors including Microsoft Word.

The graphics for the RTF report are written in both Bit Map (BMP) and Meta File formats

(WMF). The graphics are only maintained for the current nodal analysis file and are located

un der th e Pr ogra m Files\ Gemini\ Avalon\ XFiles\ Bitmaps folder or wherever AVALON was

insta lled. The gra phics included in the RTF files ar e in the BMP form at . Upon importing the

RTF file into a word processor the user may wish to replace the Bit Map graphics with theMeta F ile gra phics located in t he gra phics folder.

2 .5 - Expor t i ng P i c t u res an d Form s t o Ot her W i ndow Program s

It is often convenient to export the other pictures and/or forms in AVALON to other

window program s. To accomplish th is highlight t he form , and simu ltan eously hold th e Alt an d



Ch ap ter 2 : Using AVALON

17

Pr int Scrn keys down to copy the pictur e to the clipboar d. Now paste t he captur ed screen t o

th e destinat ion windows application. Most user s find th is the preferred way to print pictu res -

ma ps can easily be integr at ed int o word processor docum ents . This featu re supplement s the

graphics created in the previous section

2.6 - Us ing On l in e Help

The online Help system r eferences near ly all aspects of AVALON. It contains extensive

inform at ion on the basics for us ing Avalon beyond wha t is found in th is man ua l. You can

access online Help through the Help menu Content command, search for specific topics with

th e Help Sear ch tool, or pr ess F1 t o get cont ext-sensitive Help.

2.6.1 - Help Con te n ts

For information on Help topics, choose Contents from

the Help menu or press F1 and click the Contents button.

You can use the Contents screen to jump to topics that tell

you h ow to use APPREN TICE, or t o get qu ick a ccess to key

reference topics.

2.6.2 - He lp In de x

The fastest way to find a particular topic in Help is to

use th e H elp Topics dia log box below.

To display th e Help Topics dialog box, you can

either choose Index from the Help menu or click the

Sear ch button on any Help topic screen. Sear ch topics are given as green text th at is solidly

underlined.

T o s e a r c h H e l p




18

1. In the Help menu, choose Index. (you

can also click the Search button from

an y Help t opic window.)

2. In th e sear ch dialog box, type a word, or

select one from t he list by scrolling u p or

down. Pr ess ENTE R or choose Show

Topics to display a list of topics related

to the word you specified.

3.

Select a topic name, and press ENTERor choose Go To to view the t opic.



Chap te r 3 : Ava lon the Bas ics

19

3AVALON - t h e b a sics

3.1 - In trod u ct ion

The AVALON nodal ana lysis program can be used for 3 fun damen tal ta sks. The first ta sk is basic tubing curve design with an option to include simple radial flow equations for

representing the reservoir. The second task is basic tubing curve design including two

sensitivity variables. Lastly tubing curves can be calculated and assigned to the Merlin

reservoir simulator au tomat ically. Lets look at each of th ese tasks in deta il.

Ch 3 A l h B i



Cha p te r 3 : Ava lon the Bas ics

20

3 .2 – N O D A L A N A L Y S I S D E S I G N – t h e b a s ic s

This section will provide a cookbook approach for creating standalone nodal analysiscurves. These cur ves represen t t he oil, water a nd gas delivera bilities under different plumbing,

bottom hole and surface pressure conditions. Engineers can use these curves to design

accepta ble tu bular ’s to meet th e ant icipated reser voir production ra tes. In conjun ction with

the Merlin simulator as will be seen later the optimal plumbing can be estimated for each

reservoir pr oduced.

The following recipe provides an acceptable work path for creating AVALON tubing curves,

and creat ing a report of the results.

1 Select New Nodal File under the File

menu. Type a file name in the dialog box

that appears. The extension NOD is used

for all n odal file.

Chap te r 3 : Avalon the Bas ics




21

2 Fill in a description of

the reservoir followedand click the Oil/Gas box

under the Description

frame.

3. Under C a l c u la t i o n D e s ir e d

clicked either Gemin i Noda l

Analys i s Tab les for

generating Merlin tubing

curves or Nodal AnalysisSens i t i v i ty S tud ies for

generating standard nodal

analysis tables. If G e m i n i

Nodal Analys i s Tab les is

selected then the P r e s s u r e

Calcu la t ed At box will not

appear because by default

the pressure is calculated at

bottom hole conditions for known su rface pressur es.

4. Under the Nodal menu click G e n e r a l

Op t ions . A series of folders will appear

with general items to fill out for the nodal

analysis calculations.

5. Under Case S tudy Var i ab le ( s ) select

what 2 variables you wish to vary. In the

selection here the effect of both pipe

roughness and vertical tubing size will be

an alyzed. Pipe roughness var ies from 0

(smooth) to 0.1 (rough), and tubing size

varies from 2 to 4 inches in one inch

increment s. The case stu dy variables ar e

applied to all tubing segments if moreth an one node exists for a well. If less th an

Cha p te r 3 : Avalon the Bas ics




22

2 case study intervals are desired set t he nu mber of intervals to one.

6. Under P VT fill out the

appropriate boxes. Correlations

ar e provided for ma ny of the fields

– data can either be entered if

known or calculated from a

correlation if unknown.

7. Under Opt ions – Se tup an inactive gas lift design button is present. Gas lift

calculations were n ot included in th is release.

8. Under C o r r e l a t i o n s the

vertical pipe, horizontal flow

line, PVT, and reservoir

corr elations can be chosen. If

these values are not chosen

default correlations will be

used.

9. Under G e n e r a l a variety of

general parameters are

required for the nodal

calcula tions ar e given. These

variables include the number

of vertical and horizontal

pipe segments used in the

iterative nodal analysiscalculations, pipe roughness,

Chap te r 3 : Avalon the Bas ics




23

an d separ at or and wellhead conditions .

10. If a reservoir module is present under the

N o d a l home form menu select R e s e r v o i r

and Wel l Op t ions . This men u is only

selected if the user wishes to include

approximate reservoir performance curves in

his nodal analysis calculations. These curves

will never be used by Merlin, since Merlinprovides the reservoir module for these cases.

The various wells can be selected and

appropriate well test information can be

included to improve the accuracy of the

reservoir performance curves. If reservoir

performance curves are calculated they are

included in all graphics. On the other hand if

th e reservoir module is ignored these curves will be absent from t he plots made lat er.




p

24

11. Select Define Nodes, Calculate

under the Nodal menu on the

home form. The Nodal Setup

form that is used to design

tubing layout, calculate tubing

curves, and display the results

should now be visible. This form

is divided into five different

ar eas by boun ding fra mes.

The first frame is describedas the Node Descr ip t ion frame,

and contains all of the

information for the currently

selected nodal analysis well.

Different segments can be

selected – for example,

horizontal, vertical, choke, or

safety valve. The vertical node can be used for either vertical or inclined segments

below th e sur face.

As different segment s ar e added t o a well the pictur e of the well in t he p i ct u r e b o x

changes. For example in the well shown in this picture box there are 2 vertical

segments and one horizontal segment. The segment selected is node number 1 which

corresponds to the horizontal flow line segments that is 400 feet long. The surface

pressures specified (or calculated for a well with surface pressures calculated)

corr esponds t he su rface pressur e at th e end of the horizont al flow line shown for well 1.

Clicking on different segments in t he pictur e box automat ically updat es th e well’s node

description in the Node Descr ip t ion box.

Th e Def ine Well s options allow the user to create new wells, delete wells, and add or

delete nodes for a well.

Once the wells are defined the nodal analysis curves can be calculated by clicking the

Al l Noda l Cur ves button under th e C a l c u la t e R e s u l t s F o r selection. If th e tu bular

design for only one well were changed click the N o d a l C u r v e S e l e c t e d button to

upda te th e calculations for only th is cur ve. Please note that all calculat ions mu st be

performed before a ny resu lts can be displayed.




25

Once the well calculations

have been completed under

results click either Nodal

C u r v e S e l e c t e d to displaythe highlighted curve under

Def ine Wel l s or All Nodal

C u r v e s to plot all of the

curves simultaneously. The

last plot layout used will be

used to make plots when the

Plo t button is clicked. The

plot layout can be changed by

selecting Des ign P lo t

L a y o u t before the graphics

are plotted, or alternatively

by selecting t he P l o t L a y o u t

option under Format after

th e plot is displayed. The

Plot Layout window is shown below. P i p e R o u g h n e s s is the variable across the page

and Ver t i ca l Tub in g S ize is the variable down the page. Multiple plots per page were

selected a nd t he layout on th e individual plots is given in t he gra ph window.




26

The resulting plots for the layout selected above is given below.

To blow up individual plots to full screen click on the plot desired. Click again to see all

of the original plots.




27

3.3 – Creat in g a R eport

Avalon has a sophisticated reporting option

that allows the user to create customized

reports for migration to Word Processors such

as Microsoft Word. The reports ar e written in a

Rich Text format to be compatible with most

other Windows applications. The procedur e for

creating RTF reports is given below.

Once a plot or group of plots have been

displayed the user can pick either the Save

I m a g e o f C u r r e n t P i c t u r e to save what is

visible on the current form, or alternatively the

Exi t /Save Al l P i c tu res to save all of the

pictur es tha t can be displayed. The pictur es are

saved in both a Bit Map format (BMP) and a

Windows Metafile (WMF) format. The WMF

format is not used in the report generation

process, but the WMF files are saved for later copy and paste operations in other Windows

applications. The graphics are only maintained for the current nodal analysis file and are

located un der th e Progra m Files\ Gemini\ Avalon\ XFiles\ Bitma ps folder, or wherever

AVALON was installed.

Next un der t he View option for t he

Node Setup form select Report to

start the report generationprocedure. The steps for creating a

report will pop up in the white

space as shown below.




28

The next step is to select what will be displayed in the report. Under View select R e p o r tOp t ions , and choose the text and plots to be displayed. No plots can be displayed until first

included by clickin g th e Plot option on th e Nodal Setu p form. In t he selection below all text

except the values for the nodal curves, and all graphics as well are displayed. Click Save t o

save th e reporting options.




29

Lastly click View Repor t under

View to View the RTF report.

The top of the report for the

selection above is given below.

Under File select Save Report to

save the RTF report. RTF

reports are large so it is

recommended to open these

report s with your word pr ocessor

and save to the word processorformat as soon as possible. The

RTF reports should be viewed as

a temporary report because the

RTF format is not particularly

efficient. Of course if you have

enough hard disk space keeping

the RTF formats may still be

desirable becau se th ey are so genera l. If your word processor can not h an dle RTF files you can

always elect t o open t he file with WordP ad.

Once the RTF file has been opened in a word processor you may find that the conversion was

not 100%. For example you may need to add tabs to keep columns lined up. We have found

that unfortunately the conversion process is not without errors. In addition you may wish to

replace the BMP graph ics with WMF graph ics stored und er th e \AVALON\ Xfiles\ BitMaps\

folder.

3.4 – Plots A va i la ble

Avalon has the ability to generate a variety of plots depending on the setting chosen. As we

have seen nodal analysis curves can be created for either oil or gas reservoirs, a reservoir

module can optionally be included, and the pressures can be fixed at either bottom hole or

surface conditions. Lets look at each of the plot types graphically to understand what is

possible.




30

3.4.1 – Gas r eservoir w ith sur face pr essur e f ixed

The first case we would like to

examine is a gas reservoir without a

reservoir module. The results for this

case are given to the right. Note that

the right mouse key was clicked to

highlight 2 different points. The legend

shows the surface pressure range, the

X axis shows th e various gas ra tes, and

th e Y axis shows t he var ious calculat edbott om hole pressures. If one or more

horizontal surface segments are

included for the well the surface

pressures represent the pressures at

the end of the horizontal segments.




31

3.4.2 – Gas r eser voir with bott om h ole pre ssur e fixed

An alternative plot for a gas reservoir is to look at the effect of maximum deliverability for

different bottom hole flowing pressures. For example with a bottom hole pressure of 2000 psi

th e ma ximu m deliverability is seen t o be appr oximately 7000 MCF/D.




32

3.4.3 – Oil reser voir with sur face p ressur e f ixed a nd reser voir cu rves

Another example given below is an oil reservoir with the reservoir curves included. Note the

intersection of the reservoir and tubing curves that shows the maximum deliverability for the

cond itions chosen . In th is case to achieve a oil ra te of 6927 BOPD th e bott om hole flowing

pressu re is 7718 psi, an d th e corresponding reservoir pr essure is 10000 psi.




33

3.4.4 – Tub ing cu rve s with sen sitivities

Section 3.3 illustr at ed genera tion of tu bing cur ves with sensitivities to both pipe roughness

and vertical tubing size. This plot has been reproduced below. A variety of other sensitivity

studies are possible for various combinations of variables listed on the Nodal Analysis Setup

form.



Cha p te r 4 : L ink in g AVALON to MERLIN



36

nodal analysis tables and then linking the various nodal curves to different wells in Merlin.

Let’s look a t t his last step in detail.

After generat ing nodal analysis cur ves the user m ust link t he well nam es in Merlin t o nodal

well curve names. Any Merlin well not assigned a tubing curve will use the conventional bottomhole pressure constraint. To link the Merlin wells to tubing curves first select the Assign

Noda l Curves t o Wel ls i n Mer l in button under the Nodal Setup form. Line up the Merlin

Well names a nd t he Matching Nodal cur ve names an d click th e import ar row button to link th e

two entr ies. Reassigning the n odal cur ves to the Merlin wells here will overwrite an y previous

tu bing cur ve assignmen ts done in Merlin.

Lastly, under the home form select Fi l e /Save Mer l in F i l e to save the tubing curves and

corr esponding well assignment s t o the various Merlin wells.

4.2.2 - Int er act ively Designin g Sur face Fa cilities

Avalon has a feature that allows horizontal tubing segments to automatically be edited to

go to different p lat form s or collection points. The pr ocedur e for a ccomplishing th is ta sk is

given below.

The first step is to create nodal analysis curves with one or more horizontal flow line

segments, the number of which depends on how many kinks are required to properly model to

surface flow line path. Assign some arbitrary length to each segment. These lengths will be

inter actively modified to reflect th e sur face facility design chosen later .

Next assign t o nodal curves to various wells in Merlin u sing th e Ass ign Nodal Cur ves to

Well s i n Mer l in button discussed in the last section. The last step is to click the Design

F l o w L i n e s button under the Merlin Link frame. This will open a picture box that contains a

plane view of the reservoir with the well locations specified in Merlin. The user can

interactively move the horizontal flow line segments and when the Form/Save button is

clicked th e new lengt h an d position of each horizonta l flow line segmen t is calculat ed. An

example of a horizont al flow line before an d a fter corr ect placement using t he m ouse is shownbelow.

Chap te r 4 : L ink in g AVALON to MERLIN



37

Separ at or facilities can also be deleted, added, or m oved by first clicking t he object t o be

moved with th e mouse.

Well Placement before adjust ing th e horizont al flow segment s. Merlin well P1 a ssigned t o nodal

curve well1.

Well Placement after a djusting th e horizont al flow segments a nd separ at or position.




38

4.3 – Using Merl in Wi th Tu bin g Curves

After integrating tubing curves into a Merlin file with Avalon the next step is to perform

reservoir simu lation with Merlin, and gain an under stan ding of how the pipe design will affect

production. The lat est ver sion of Merlin cont ains modificat ions to th e Well Description form to

include changing tubing curves for any well at any time step. This particular feature is absent

in Avalon wher e only the initial t ubing curves for m aking ru ns a re set.

Often you may find that after making a few runs in Merlin you need to reenter Avalon,

adjust the tubing curves based on results observed in the Merlin simulator, and reassign the

tu bing cur ves to the Merlin file. This iterat ive procedur e allows a simple tr ial and err or path

for optimizing tubin g cur ves for differen t wells in different par ts of th e reservoir. An appr oach

like this represents something that is rarely done in modern reservoir simulation, and

repr esents a m ajor step forwa rd for designing the developmen t of fields. This ability is greatly

enha nced by the su rface facility inter active design featu res discussed in t he pr evious section.

Chap te r 4 : L ink in g AVALON to MERLIN



39

4.2.1 – Histor y Match ing Historical Well Flowing P re ssur e Dat a

Avalon does not have a stand alone history match feature at this time. To adjust the tubing

curves to match known flowing tubing head data the following work flow procedure is possible.

First generate approximate tubing curves in Avalon and assign to the appropriate wells in

Merlin. Next open Merlin and assign the historical flowing tubing head pressures for the

various wells. Run the model in Merlin and use the Output/Well Data to view the flowing

tubing head pressure h istory ma tch. If it is una cceptable reenter Avalon a nd recreate adjusted

tubing curves (for example change the pipe roughness). Reassign the tubing curves to Merlin

and test the history match for flowing bottom hole pressures.




40

I n d e x



2

I n d e x

A

All Nodal Curves, 25

Assign Nodal Curves to Wells in Merlin, 36

B

Backups, 12

Bit Map, 27

blow up individual plots, 26

BMP, 27

bottom hole pressure, 31

C

Calculate Results For, 24calculate tubing curves, 24

Case Study Variable , 21

choke, 24

Correlations , 22

D

Define Wells , 24

deliverability, 31Design Plot Layout, 25

design tubulars, 24

display the results, 24

E

Exit/Save All Pictures, 27

Exporting Pictures and Forms, 16

G

Gas lift calculations, 22

Gemini Nodal Analysis Tables, 21, 35

General Options , 21

H

Help, 17

Help Index, 17

History Matching, 39

horizontal, 24

horizontal flow segments, 37

I

inclined segments, 24

install, 10

install, two machines, 12

installation, 10

M

Merlin, 36

Merlin Well names, 36Metafile, 27

minimum requirements, 10

N

network, 12

Nodal Analysis Sensitivity Studies, 21

Nodal Curve Selected, 25

Nodal Setup, 28Node Description, 24

Nodes, 24

I n d e x

O Save Image of Current Picture 27



2

O

Oil reservoir, 32

P

pipe roughness, 21, 22

plot, 25

Plot Layout, 25

Plots, 29

Pressure Calculated At, 21

Printing, 16

PVT, 22

R

recipe, 20

Report, 27

Report Options , 28

Reservoir and Well Options , 23

reservoir module, 23

reservoir performance curves, 23RTF reports, 27

S

safety valve, 24

Save Image of Current Picture , 27

Save Merlin File , 36

sensitivities, 33

sensitivity variables, 19

separator, 23separator position, 37

Surface Facilities, 36

T

Toolbox, 35

tubing curve design, 19

V

vertical, 24

vertical tubing size, 21

View Report, 29

W

Well Placement, 37well test, 23

wellhead conditions, 23

Windows Metafile, 27

WMF, 27

Word Processors, 27

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