62589751 Manual de Simulador Pipe Phase

5/21/2018 62589751 Manual de Simulador Pipe Phase

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INTRODUCTION TO

PIPEPHASE


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Introduction to PIPEPHASEWorkbook

The software described in this document is furnished under a license agreementand may be used only in accordance with the terms of that agreement. Informationin this document is subject to change without notice. Simulation Sciences Inc.assumes no liability for any damage to any hardware or software component or anyloss of data that may occur as a result of the use of the information contained in thisdocument.

Copyright Notice Copyright 2001 Simulation Sciences Inc. All Rights Reserved. No part of thispublication may be copied and/or distributed without the express written permis-sion of Simulation Sciences Inc., 601 Valencia Ave., Brea, CA 92823-6346.

Trademarks PIPEPHASE, NETOPT, TACITE, and SIMSCI are registered marks and/or trademarksof Simulation Sciences Inc.

Windows, Excel, and MS-DOS are registered marks and/or trademarks of MicrosoftCorporation.

All other products are trademarks or registered marks of their respective compa-nies.

Printed in the United States of America, J uly 2001.


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Introduction to PIPEPHASE i

Contents

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Exploring the PIPEPHASE Desktop . . . . . . . . . . . . . . . . . 5

Defining the Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Setting the Input Units of Measure . . . . . . . . . . . . . . . . . . 22

Entering Thermodynamic or PVT Data . . . . . . . . . . . . . . 24

Specifying the Global Defaults. . . . . . . . . . . . . . . . . . . . . 31

Building the Flowsheet . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Entering Source and Sink Data. . . . . . . . . . . . . . . . . . . . . 36

Defining Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Setting up a Case Study . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Working with Keyword Input Files. . . . . . . . . . . . . . . . . . 53

Running the Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Viewing the Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Fluid Flow Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Applying PIPEPHASE to Downhole Operations . . . . . . . 87

Executing a Sensitivity (or Nodal) Analysis. . . . . . . . . . . 98

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
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Introduction to PIPEPHASE 1

Introduction

PIPEPHASE is a steady-state multiphase fluid flow network simulator

used for the rigorous modeling of oil and gas gathering and transporta-tion systems. PIPEPHASE provides integrated solutions to network

problems. It can perform distinct analyses of individual nodes separately

and it is also able to incorporate the parameters of interrelated nodes into

the total solution. The applications of PIPEPHASE range from the sensi-

tivity analysis of key parameters in a single well, to a multi-year facili-

ties planning study for an entire field. This program also combines an

efficient multiphase network solution algorithm with modern oil and gas

production analysis techniques to create a unique field design and plan-

ning tool. This is coupled with an extensive physical property databank,

and integrated with an intuitive Windows-based user interface.

CalculationEngine

PIPEPHASE technology includes:

Comprehensive physical properties databank and thermodynamic

capabilities

Fluid types, such as, blackoil, compositional, liquid, gas, steam, and

multiphase mixtures of gas and liquid

Link devices: pipes, tubing, compressors, pumps, separators, IPRs

Well analysis with inflow performance

Gas lift analysis

Pipeline sphering

Sensitivity (nodal) analysis

PIPEPHASE also comes with two add-on modules, NETOPT and TAC-

ITE, which can be installed at the same time as PIPEPHASE provided

you have obtained the appropriate security. Contact your sales represen-

tative for more information.

NETOPT

NETOPT provides you with optimization capabilities that allows you to

optimize network performance by defining specific operating objectives

while satisfying both physical and user-imposed constraints. For exam-

ple, you can use NETOPT to maximize the oil production from a system

of wells operating under injection-limited gaslift, or minimize capital

costs for a new pipeline system.


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2 Introduction

TACITE

The TACITE code, developed by IFP, Elf Aquitaine and TOTAL, is a

compositional transient multiphase flow simulation tool, for the design

and control of oil and gas production pipelines and wells. The program

simulates the transient behavior of a fluid flowing through a single-link

flow system. The source flowrate and sink pressure are specified as time-dependent boundary conditions.

GraphicalUser

Interface

PIPEPHASE GUI features include:

A true 32-bit Windows-based application

Interactive data entry and execution

Generate graphs, tables, and charts; view in Microsoft Excel

On-line help with hypertext jumps

And many more.

This comprehensive range of features enables your company to use one

simulator for all phases of business.

PIPEPHASEEngine/GUI

Relationship

PIPEPHASE was originally designed with an easy-to-use keyword ver-

sion, where input information was entered through a text editor. The cur-

rently enhanced Graphical User Interface (GUI), however, provides a

more user-friendly and interactive environment for data input and flow-sheet construction. Although familiarity with the keyword structure can

be useful in executing and troubleshooting simulations, this class will

focus solely on the GUI for several reasons. The GUI prompts you for

the necessary input data, making it easier for you to see what is missing

from a particular simulation. Furthermore, the GUI provides a visual

description of the process, giving you a better feel for the simulation.

Figure 1 :

PIPEPHASE

ComponentsPIPEPHASE

Graphical UserInterface

PIPEPHASE

Graphical UserInterface

PIPEPHASEDatabase

PIPEPHASEDatabase

PFE TextEditor

PFE TextEditor

PIPEPHASECalculation

Module

PIPEPHASECalculation

Module

PIPEPHASEKeyword File

PIPEPHASEKeyword File

PIPEPHASERAS

PIPEPHASERAS

PIPEPHASEReport File

PIPEPHASEReport File


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Where to Find Additional Help

DocumentsUser manuals are shipped with your copy of PIPEPHASE. A complete

set of documents is provided on the CD in the form of .PDFfiles that are

most conveniently viewed using Adobe Acrobat Reader, supplied on the

installation CD. If you required additional manuals, contact your sales

representative.

Online Help PIPEPHASE comes with online Help, a comprehensive online referencetool that accesses information quickly. In Help, commands, features, and

data fields are explained in easy steps. Answers are available instantly,

online, while you work. You can access the electronic contents for Help

by selectingHelp/Contentsfrom the menu bar.

TechnicalSupport

PIPEPHASE is backed by the full resources of Simulation Sciences Inc.

(SIMSCI), a leader in the process simulation business since 1966. SIM-

SCI provides the most thorough service capabilities and advanced pro-

cess modeling technologies available to the process industries. SIMSCI's

comprehensive support around the world, allied with its training semi-

nars for every user level, is aimed solely at making your use of PIPEP-

HASE the most efficient and effective that it can be.

SIMSCI offers technical support for PIPEPHASE for all questions sentby fax, E-mail or regular mail. In North America, call our hotline sup-

port at 1-800-SIMSCI1. When contacting Technical Support, please

include the following in your correspondence:

Name and company, phone and fax numbers

Product version number

Problem description, including any error messages that you received

and the steps necessary to duplicate the problem

If you are e-mailing your problem, please include an electronic copyof the .INPor .PP0and .PP1files.

When calling in a request, please have this workbook available and

be near your computer to be able to walk through any difficulties.


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4 Introduction

About This Workbook

This workbook complements SIMSCI's Introduction to PIPEPHASE

training course. Since much of the course time is dedicated to hands-onexamples, you will not necessarily go through the document page by

page. The workbook does, however, follow the course sequence and you

may want to jot notes in the margin. We strongly recommend that you

read this workbook from cover to cover once and then use it to refresh

your memory later on.

Conventions Before you begin this workbook, you should be aware of several conven-tions. These include:

Italicized text denotes menu items, dialog box names and fields, andlists. For example, File, Save As..., the Source Datadialog box, and

CompositionDefined.

Buttons within dialog boxes are represented as gray-filled boxes

with white overlaid text, such as , , and .

... Ellipses indicate items that, when selected, bring up a windo

or dialog box, for example, and .

Text in < > brackets indicates keyboard strokes.

The,icon indicates a cautionary note or a useful tip.

SIMSCI has made great efforts to ensure that PIPEPHASE is compliant

with Microsoft Windows. As a result, much of what follows will be very

familiar to experienced Windows users.

Click,Highlightor Select: Place the pointer on the item and press the

left mouse button.

Double-click: Same as click except you press the left mouse button

twice with only a very short pause between clicks.

Open: To open a dialog box or object, place the pointer on the objectand click or double-click the mouse.

Drag: Move the mouse while holding the left button down

OK Status

Add ->

M odify.. . Enter Data.. .

, Note: Remember to save your work often!


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Exploring the PIPEPHASE Desktop

The visual engineering of PIPEPHASE makes building a simulation

easy. Functional colors, menu-graphics and picture icons guide youevery step of the way. On-line references refresh your memory on equa-

tions and guidelines. And if you encounter trouble, Help is available

when you need it.

LaunchingPIPEPHASE

To initiate a PIPEPHASE session:

Click Starton the taskbar, select Programsand then SIMSCI.

Click on PIPEPHASE.

Click , then choose Filefrom the menu bar.

The Filemenu is described below.

MainWindowThe PIPEPHASE main window, shown in Figure 2, is your primaryworkspace. This window forms the interface between you and the

PIPEPHASE program. This is where you will build and run all your sim-

ulations, as well as open files, save the current data, or exit the program.

You will use all the familiar Windows features such as toolbar buttons,

menus, dialog boxes, and drop-down lists.

Table 1: File M enu Options

Option Function

New Initialize a new simulation

Open Open an existing simulation

Import Keyword File Load a keyword input file into PIPEPHASE

Close Close the active simulation

Save/Save As Save the active simulation to a file with the same name, or to a new file

Copy Simulation Create a new simulation as a copy of an existing oneDelete Simulation Delete an existing simulation

Run Run the simulation

Remote Settings Run PIPEPHASE calculations from a UNIX machine

View Output File View the output file in the Programmers File Editor

View Keyword File View the input file in the Programmers File Editor

Print Print the flowsheet drawing or output report

Exit Close the active simulation and exit the program

OK
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6 Exploring the PIPEPHASE Desktop

Figure 2 :

PIPEPHASE

Main Window

M enu Bar Directly below the title bar of the main PIPEPHASE window you willfind the main menu bar. It gives you easy access to the command menus.

Table 2: PIPEPHASE M ain Window Components

Component Description

Title Bar The window title contains the name of the current simulation and view.

Menu Bar All functionality can be accessed through the menus.

Toolbar Shortcut buttons for many commonly used PIPEPHASE operations areprovided. These include data entry window buttons and viewing buttons.

Primary Workspace This is where you draw your flowsheet.

Scroll Bars The vertical and horizontal scroll bars enable you to move vertically and

horizontally through a window.

Status Bar The bar below the toolbar that gives quick help on the highlighted button.

Control-menu Box The standard Windows control-menu in the top left corner can be used tomove, resize or close the application window

Table 3: PIPEPHASE M enu Bar

Me nu Ma in Functions

File File operations: open, close save, import, etc.

Edit Manipulate links and nodes on the flowsheet

View Specify what appears on the main window

General Add input data - all data can be entered from this menu

Special Features Enter case study and time-stepping data; access to a number ofperformance curves and program databases

Help Access the on-line help functions


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Many of same commands are available through the buttons on the tool-

bar.

Toolbar The toolbar appears just below the menu bar on the main PIPEPHASEwindow. Using the mouse, you can initiate many actions by clicking the

buttons on the toolbar.

Data EntryWindows

PIPEPHASE provides dialog boxes that allow you to enter data in a log-

ical manner. Throughout this workbook, you will see examples of data

entry windows. Within these dialog boxes, there are many different types

of data entry devices including check boxes, radio buttons, drop-downlists, and buttons.

Table 4: PIPEPHASE Toolbar Buttons

Button Descri ption Button Descri ption

Create a new simulation

Define hydrates

Open an existing simulation

Select units of measurement

Import a keyword input file

Select the components

Save the active simulation

Select thermodynamic method orenter PVT data

Run the simulation and review theresults

Set the calculation method

View the output file

Enter the global defaults

Print the output file or flowsheet

Define network optimization data

Add a source to the flowsheet

Zoom in on a selected area

Add a sink to the flowsheet

Zoom out

Add a junction to the flowsheet

Display the entire flowsheet in themain window

Add a calculator to the flowsheet Refresh the flowsheet drawing

Table 5 : Data Entry Wi ndow Buttons

Button Description

All data are saved and the dialog box is closed.

All data entered or modified are lost when the dialog box closes.

Displays the online help for the dialog box.

OK

Cancel

Help


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8 Exploring the PIPEPHASE Desktop

Color Cues PIPEPHASE uses color cues to inform you of the status of your simula-tion. The significance of the colors you will encounter while working

with PIPEPHASE are summarized below.

Editing andViewing the

Flowsheet

You can use the options on the Editmenu to modify the placement of

objects on your flowsheet diagram.

You can use the options on the Viewmenu to modify the data displayedon your flowsheet diagram.

Table 6: Color Significance During Data Entry

Color Significance

Red Required data is missing

Blue All necessary data has been entered

Green An item is selected

Gray Data field is not available to you

Table 7: Edit Menu OptionsOption Function

Copy Node... Copy an existing node to a new node at coordinates X, Y

Copy Link... Copy an existing link to a new link

Edit Node... Sort, edit, delete, and copy existing nodes or add a new node to the flowsheet

Edit Link... Sort, edit, delete, copy, or change the flow direction of existing links

Move Node... Move the highlighted node around the flowsheet using the arrow keys

Draw... Add text, a line, a rectangle, or an oval to the flowsheet.

Table 8: View M enu Options

Option When the option has a checkmark beside it:

View Output View node results or link plots; you cannot make data entries or edits inthis mode

Node Labels Node labels are shown on the PFD; for example, S001, D002

Link Labels Link names are shown on the PFD, for example, L001, L002

Show Pressures Defined pressures (not estimates) are displayed on the PFD

Show Temperatures Supplied temperatures for each source are displayed on the PFD

Show Rates Defined flowrates (not estimates) are displayed on the PFD

Ribbon Bar Toolbar is visible below the menu bar


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Link DeviceData Window

The Link Device Data window, shown in Figure 3, is the workspace into

which you add and define your link data for each link on the main win-

dow. To open this window, double-click on any link on the flowsheet.

Figure 3 :

Link Device Window

This window is broken up into four sections. Starting from the top left-

hand-side, these include:

Access buttonsenter and exit link device view, and open onlinehelp.

Edit link functionsedit, delete, reverse, copy and paste functions.

Calculation dataenter link data, nodal analysis data, line sizing data,

or TACITE transient data.

Devices paletteuse this toolbar to add devices to the active link; the

description for each unit is provided in the status line above the tool-

bar, for example, Pipe.
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10 Defining the Simulation

Defining the Simulation

This chapter describes the objectives, applications, and capabilities of

PIPEPHASE. It introduces the concepts involved in pipeline, well, andnetwork analysis and describes how PIPEPHASE tackles them. The

numerous simulation and fluid types available in PIPEPHASE are also

discussed.

Applications The broad applications of PIPEPHASE can be categorized into threeparts:

Single pipeline analysis

Wellbore analysis

Field wide studies

Single PipeAnalysis

PIPEPHASE is a sophisticated tool for the design and analysis of single-

phase and multiphase pipelines. The main features of PIPEPHASE

involve capacity calculations, condensate drop-out problems, CO 2/

Steam/N2 injection networks, and heated oil pipelines. The rigorous

energy balance and detailed heat transfer model enable the accurate sim-

ulation of viscous fluids in insulated and/or heated oil pipelines as well

as steam injection systems.

Capacity calculations form the core of any preliminary process design.

PIPEPHASE allows you to specify the desired parameters in a particular

field, and accurately calculates the operating conditions necessary to

accommodate these values. For instance, as a simple example, if one is

given a specified inlet and a desired outlet pressure at a given flow rate,

PIPEPHASE calculates the pump power needed to meet these specifica-

tions. You could also use line sizing to vary the diameter of the pipes

used in order to provide an optimal estimate for the size of the pipes.

Figure 4 :

Capacity Calculations

PIPEPHASE also accurately predicts retrograde condensation, or con-

densate drop-out problems, in wet gas pipelines. The retrograde phe-

nomena is graphically illustrated in Figure 5. Conventional techniques

that employ extrapolation to predict the point of retrograde phenomena

are invariably incorrect. PIPEPHASE applies a point-by-point PVT anal-

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ysis, which has proven to be extremely accurate. This is especially useful

when exact solutions are desired.

Figure 5 :

Phase Envelope

Steam I njection Networks

In steam injection networks, PIPEPHASE allows you to develop operat-

ing conditions that will minimize heat loss in the network and optimize

energy usage. Large networks require an optimal distribution of heat for

maximum energy efficiency. For instance, an even distribution of steam

injection throughout the network may not necessarily be the optimal

arrangement. Such a configuration may exceed heating requirements in

some wells and may fail to provide sufficient energy in others.

PIPEPHASE performs rigorous heat transfer calculations to fully

describe the energy requirements of each individual well, as well as the

network as a whole. Because PIPEPHASE performs a rigorous enthalpy

balance, it can be used for single component fluids other than steam.

In the example shown in Figure 6, given 600 psia steam at the inlet,

PIPEPHASE can calculate the flowing bottomhole pressure.

Figure 6 :

Steam Injection

Networks

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Heated Oil Pipelines

For heated oil pipelines, PIPEPHASE allows for the variation of node

parameters (i.e., insulation thickness, heaters, pumps) to meet the pipe

specifications. Viscosity characteristics are always taken into account,

and the flow characteristics of the fluid can be analyzed exactly. PIPEP-

HASE can perform accurate calculations in both laminar and turbulentflow regions, as well as analyze the transition region with equal preci-

sion. In the event of sludge formation, especially in heated oil pipelines,

PIPEPHASE employs a sphering or pigging model to estimate slug char-

acteristics for the design of downstream slug catchers.

WellboreAnalysis

PIPEPHASE provides a comprehensive set of features for the detailed

design of production or injection well systems. This includes detailed

reservoir inflow performance characterization, a choice of completion

models at the sandface, wellbore geometry variations to accommodate

typical production, injection or artificial lift (ESP or gaslift) operations,and surface flowline and facilities models simulating most oil field oper-

ations. Almost all of the well-known mulitiphase correlations, both

empirical as well as mechanistic, are available for a wide range of flow-

ing conditions and inclination angles.

Figure 7 :

Wellbore Analysis

The most common application of PIPEPHASE to wellbore problems is a

nodal analysis. PIPEPHASE is equipped with a sensitivity analysis fea-ture, which is a generalized nodal analysis tool. This feature can provide

graphical solutions to wellbore problems, where the solution node can be

any point along the production string, and the inflow and outflow curves

can represent composite multiple parameter behavior. For instance, in

modeling a particular well, the inflow and outflow curves can be given

by the Productivity Index IPR (inflow) and the tubinghead pressure (out-

flow). The intersection of these curves provides the solution.

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Performance Analysis

Figure 8illustrates a graphical solution to wellbore calculations. In this

case, reservoir performance is given (flowing bottomhole pressure as a

function of flow rate). The composite variable in this case is the size

(inside diameter) of the pipes. These curves are superimposed on the

graph, and the intersection of these curves with the Reservoir Perfor-mance curve indicates the solution for each case. The solution gives the

operating conditions for the node to meet the desired specifications.

Figure 8 :

Wellbore Calculations

- Varying Pipe Sizes

Figure 9is analogous to the previous example with a different variable.

Instead of varying pipe sizes, you vary well-head pressure (WHP). Also,

reservoir performance is represented by two curves, illustrating the

decline in the reservoir pressure with production. Similarly, solutions are

indicated by the intersection of the two plots, and the solutions give the

operating conditions needed for the given specifications.

Figure 9 :

Wellbore Analysis -

Varying Well-head

Pressure

PIPEPHASE also models artificial liftmethods. The two methods avail-

able to the program are continuous gas lift for enhanced fluid recovery

and electrical submersible pump analyses.

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Gas Lift Analysis

In a gaslift analysis, separator gas available from the oil well or from an

outside source can be used to increase production. The production fluid

is considered to be in the tubing and the lift gas in the annulus around it.

Using PIPEPHASE, you can investigate the feasibility of injecting gas

for continuous gaslift. PIPEPHASE has four gaslift options:

With specified oil production and lift gas rate, PIPEPHASE gener-

ates pressure profiles in the production and injection strings of the

well.

With specified tubinghead pressure, PIPEPHASE generates table of

oil production rate vs. specified lift gas rate.

With a specified range of gas injection valve locations for fixed oil

production and lift gas injection rates, PIPEPHASE calculates corre-

sponding production string pressure, and determines the injection

location which is closest to the target outlet pressure.

With a specified range of gas injection valve locations for fixed oil

production and lift gas injection rates, PIPEPHASE calculates corre-

sponding injection string pressures and determines the location

which is closest to the target outlet pressure.

Figure 10:

Gas Lift Analysis

PIPEPHASE offers you great flexibility in cases of gaslift analysis. Youcan analyze the performance of wells currently on gaslift, maximize oil

recovery using new gaslift, and determine which gaslift valves should be

activated for a specified production scheme. This allows you to study

each production well in a field over the life of the reservoir. You can also

determine which wells are candidates for gaslift, how production can be

improved with gaslift, and which gaslift rates and valve locations are

required. Once the performance of an individual well is refined using the

gaslift options, the performance of an entire gathering system can be

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analyzed in the network mode with the injection depth and rate specified

for each well.

The most common calculation in gas lift problems is the calculation of

the optimum gas injection rate. Usually, you are given the following

parameters: reservoir pressure, well-head pressure, formation gas-oil

ratio, and water cut. Injection pressure and gaslift valve locations are

usually fixed, and from this information, you must determine the opti-

mum lift gas injection rate, Q.

PIPEPHASE can generate plots of the liquid and oil production versus

gas injection rate, as shown in Figure 11,to indicate the optimum gas

injection rate required (trial injection rates are used as input to this simu-

lation to generate the desired graph).

Figure 11:

Finding the Optimum

Gas Injection Rate

PIPEPHASE also performs rigorous wellbore heat transfer calculations.These are especially useful in steam injection networks with viscous oil

(API < 10, or viscosity > 100 cP). As described previously, the object of

steam injection networks is to minimize heat loss, and PIPEPHASE

takes into account all the necessary parameters to build an accurate

model. PIPEPHASE allows user-defined input as well as default values

for pipe insulation, heat conduction, convection, heat transfer coeffi-

cients, and radiation. It also accounts for time-dependent effects through

the Ramey function.

Field WideSimulation The network simulation capability in PIPEPHASE can be used to modelthe interaction between the various elements of a complete oil or gasfield, including all of the wells, gathering and injection lines, surface

facilities, and contract delivery points. PIPEPHASE also allows the

grouping of production from the same zones for simulating time-depen-

dent reservoir pressure decline, and changing well production conditions

(increasing GOR and water cut). These capabilities have been linked

with the ability to simulate production contracts and changing facilities

to create a field planning tool.

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80 Fluid Flow Basics

Region 3: M ist Flow Region.The gas phase is continuous and the bulk of the

liquid is entrained as droplets in the gas phase. The pipe wall is coated

with a liquid film, but the gas phase predominantly controls the pressure

gradient.

Transition Region. The change from a continuous liquid phase to a continu-

ous gas phase occurs. The gas bubbles may join and liquid may be

entrained in the bubbles. The gas phase effects are predominant, though

liquid effects are also significant.

Ansari Flow Pattern Map

The Ansari correlation is also available in PIPEPHASE for modeling

upward two-phase flow. In 1988, A.M. Ansari developed a comprehen-

sive model composed of a sub-model for flow-pattern prediction and a

set of independent mechanistic models for predicting flow characteris-

tics such as holdup and pressure drop in bubble, slug, and annular flow.

The first step in this analysis is the development or prediction of flo

patterns. Based on the work of Barnea, Taitel, et.al., Ansari predicted

different flow patterns by defining transition boundaries among bubble,

slug, and annular flows. This Ansari Flow Pattern Map is shown in Fig-

ure 48.

Figure 48:

Ansari Flow Pattern

Map

Boundary Ashows the transition from Bubble to Dispersed Bubble flow

which occurs at high liquid rates. In this transition, turbulent forces

break large gas bubbles down into small ones.

Boundary B shows the transition from Bubble to Slug flow, which is

characterized by the coalescence of small gas bubbles into large Taylor

bubbles.

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Applying PIPEPHASE to Downhole Operations

PIPEPHASEs downhole capabilities include the following applications:

Gas Lift Analysis

Electrical Submersible Pump (ESP)

Time Dependent Production Planning

Gas lift analysisis used to investigate the effects of lift gas on well pro-

duction. Another common method of artificial lift is the electrical sub-

mersible pump (ESP) . These pumps improve the productivity of wells

with flow rates ranging from a few hundred barrels to tens of thousands

of barrels per day.

Production planning involves the time-dependent interaction between

the producing formation(s), and all of the wells, gathering lines, and sur-

face facilities in an oil or gas field, and the impact of this interaction on

the overall development strategy of the operating company. PIPEPHASE

supplies this capability through its time-stepping feature.

Gas LiftAnalysis

ProblemThe bottom hole pressure is too low to support the fluid column

in the well.

RemedyReduce the density of the fluid column by injecting gas into thetubing.

DilemmaGas injection creates additional back pressure which reduces

production rate.

Reservoir pressure decreases gradually once a field is brought into pro-

duction. Often there arise situations where the reservoir pressure

becomes so low that it is insufficient for the well fluids to reach the well-

head. In these cases, the pressure in the tubing must be artificially

boosted, or lifted, to enable the reservoir fluids to reach the surface. Such

procedures can be performed by using artificial lift methods. Gas lift isone of the more common artificial lift methods used in the petroleum

industry. Other methods include sucker rod pumping, electric submers-

ible pumps, and plunger/chamber lift, to name a few.

In gas lift, the object is to introduce gas near the bottom of the tubing

string. This injected gas lightens the fluid between the injection point

and the wellhead. Thus, the available bottom hole pressure becomes suf-

ficient to lift this column of aerated fluid to the top. Gas can be injected


92/101

88 Applying PIPEPHASE to Downhole Operations

continuously (continuous gas lift) or in spurts (intermittent gas lift).

PIPEPHASE allows you to model a continuous gas lift analysis, in

which you can specify the fluid properties of the gas, specify valve loca-

tions, as well as other parameters.

Figure 53shows a typical gas lift installation where gas is injected down

a packed annulus and oil and gas are produced through the tubing.

Although the reverse case is sometimes possible (though very unusual),

it is not presently supported by PIPEPHASE.

Figure 53:

Gas Lift

In this case, we assume that the static fluid level is somewhere between

the topmost valve and the wellhead. Once gas is injected through the

annulus, the topmost valve is designed to open first. This lightens thefluid above the topmost valve, causing a reduced pressure on the valve

second from the top. The second valve then opens, injecting more gas

into the tubing. This process repeats as more and more valves keep open-

ing. Once a lower valve opens, the upper valves are normally designed to

close. You will see that the gaslift effects generally increase with depth.

Only the bottom most valve allows gas passage into the tubing. This is

called the operating valve . The valves above this one merely help in

bringing the well into production (i.e. unloading the well). They are

therefore called unloading valves. In steady-state operation, PIPEP-

HASE can calculate the depth of the operating valve.

Designing aGas LiftSystem

The main problems faced by the engineer in gaslift design include:

How much gas should be injected?

At what depth should gas be injected?

What is the casing head pressure limit?

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What is the wellhead pressure required for target flowrate?

What is the depth of the operating valve?

There are four options in PIPEPHASE for gaslift analysis:

Generate the pressure profile for afixed oil production and lift gas rate.

Generate a table of oil production ver-

sus lift gas rate for fixed pressures.

Locate the gas injection valve to match

required tubing head pressure.

Locate the gas injection valve to match

required casing head pressure.

This dialog box appears as part of the simulation definition, and there-fore you must enter data into one of these options before continuing on

to the next dialog box. You can access these options again anytime by

selecting Special Features/Gas Lift...from the menu bar.

Gaslift analysis is limited to single link, black oil, continuous gaslift sys-

tems. You must follow certain basic rules when setting up gaslift prob-

lems, such as:

1. PVT data sets must be available for both the produced reservoir fluid

and the injected gas.

2. The production string is automatically named PROD and the gasinjection string (annulus) is named GASL.

3. Gas injection rates are user-specified.

Option 1 Pressure Profi le

In Option 1, Pressure Profile, the casing-head pressure and the lift-gas

injection rate are fixed. Given values for these parameters, PIPEPHASE

calculates the pressure profiles in both the annulus and the tubing for the

corresponding production rate.

When specifying a gaslift calculation with this option, PIPEPHASE willprompt you to enter values for the lift gas injection pressure and temper-

ature at the casing head, lift gas injection rate, and the vertical depth

from the well head to the lift gas injection valve. You can also enter the

percent of soluble lift gas which dissolves in the well fluid. This value is

defaulted to 100%, and generally should not change.


94/101


Figure 54:

Option 1: Pressure

Profile

Since you know the injection rate along the well depth, obtaining the

annulus pressure profile is relatively simple. Pressure profile calcula-tions in the tubing are done as follows:

1. As oil rate is fixed (calculated from the injection rate), the bottom-

hole flowing pressure is known, then

2. Use formation GOR to calculate the pressure gradient from the bot-

tomhole to the operating valve,

3. Use total GOR (formation = injection) to calculate the pressure

traverse from the operating valve to the wellhead.

Option 2 Injection PerformanceIn Option 2,Injection Performance, PIPEPHASE generates a table of oil

production versus lift gas rate, given fixed values for wellhead pressures,

valve depth and the casing-head pressure. When selecting gaslift option

2, PIPEPHASE will ask you to further specify the injection rates. You

can specify up to nine lift gas injection rates in standard gas volume

units, and all entries must be greater than zero. As in option 1, you can

also enter a value for the percent solubility of the lift gas in the well fluid

(generally 100%).

For each gas injection rate, there will be an oil flow rate that satisfies the

system constraints. At lower gas injection rates, increasing the rate light-ens the well fluid and therefore causes a production increase. However,

at higher injection rates, the frictional losses in the tubing may be so high

that this trend is reversed. There is, therefore, an optimal injection rate,

as shown in Figure 56.

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95/101


Figure 55:

Option 2: Injection

Performance

Figure 56:

Example GasInjection Curve

Note that continuously increasing lift gas rate does not necessarily resultin increased production rate. When frictional forces dominate, higher

injection rates actually decrease production. The optimal gas injection

rate and the corresponding oil production achievable are indicated by the

arrows.

Option 3 Valve Location - Fixed Tubing Head Pressure (THP)

When you select gaslift option 3, Valve Location - Fixed TH , PIPEP-

HASE will prompt you to specify lift gas injection temperature and pres-

sure at the casing head, injection rate, and up to eight vertical depths

from well head to lift gas injection valves. From these specified values,PIPEPHASE will then locate the gas injection valve to match the

required tubing head pressure. Figure 57shows a plot of injection depth

versus the production string outlet pressure, which you must also spec-

ify. Note that greater injection depths process higher wellhead pressures.

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96/101


Figure 57:

Option 3 : Valve

Location -

Fixed THP

Option 4 Valve Location - Fixed Casing Head Pressure (CHP)

Option 4, Valve Location - Fixed CH , generates a casing head pressure

versus gas injection depth curve. PIPEPHASE models valve perfor-mance by using the orifice gas pressure drop equation. Identical to

option 3, PIPEPHASE prompts you to enter values for lift gas injection

temperature and pressure at the casing head, injection rate, and up to

eight vertical depths from well head to lift gas injection valves. Also,

you can enter the percent solubility of the lift gas in the well fluid, which

is generally 100%.

Figure 58:

Option 4 : Valve

Location -

Fixed CHP

Gaslift option 4 allows you three additional entries:

1. Orifice inside diameters corresponding to the gas-lift injection

valves.

2. Inside diameters of tubing above gaslift valves corresponding to the

gas-lift injection valves.

3. Orifice coefficients corresponding to the gas-lift injection valves.

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97/101


ElectricalSubmersiblePump (ESP)

Electrical Submersible Pumps

(ESPs) are applicable to a wide

range of operating conditions: deep

formations, high viscosity fluids,

directionally-drilled wells, etc. The

primary limiting factor in the effi-cient operation of an ESP is the

amount of associated free gas pro-

duced. Free gas (as opposed to gas

in solution), which in limited quan-

tities actually improves operation

(by increasing overall fluid buoy-

ancy), also progressively degrades

performance due to cavitation, ulti-

mately creating a gaslock, at which

point the pump ceases operation. T

prevent such performance degrada-tion, free gas is frequently (par-

tially) separated downhole, and re-

introduced into the production

stream downstream of the chok

(venting to the atmosphere not being permitted in most areas).

The ESP model in PIPEPHASE simulates a downhole pump in terms of

its effects on the hydraulics of the well-bore. This includes logic to han-

dle specific features such as gas separation at the inlet (and subsequent

re-injection at the surface), and the effect of viscosity on pump perfor-

mance.

Clicking the ESP button in the Link Device Data window brings up the

Electrical Submersible Pumpdialog box, shown in Figure 59. This is the

original Pumpdialog box with an additional button for the entry of ESP-

specific data.

Figure 59:

Electrical

Submersible Pump

Dialog Box
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98/101


There are two categories of data entry under the Electrical Submersible

Pumpdialog box. The first category is for data specific to the pump, and

the second for data specific to a downhole separator located immediately

upstream of the pump (to reduce the gas ingestion). Pump-specific data

include auxiliary power, submergence depth, casing head pressure, and

the vertical pressure gradient. A check box for the Riling correction fac-tor is provided for viscosity-related corrections to the pump performance

curves. The Head Degradation Curve (maximum of 5 points) allows the

specification of degradation as a function of gas fraction. When a down-

hole separator exists, you are prompted for the separator name, and

either the gas ingestion percent (GIP) rate for the pump, or the pump OD

and casing ID, to calculate the GIP internally.

Under the Electrical Submersible Pump Curve dialog box, you have a

choice of entering up to ten data points or the three constants in each of

the quadratic equations representing the head, efficiency and horsepower

in terms of the in situ volumetric flow rate.

Time-Stepping

ProductionPlanning

Although PIPEPHASE is a steady-state simulator, it can accurately

model well behavior over an extended period of time. Typically, the time

period of analysis extends from a few years to the entire producing life

of the field. For such periods, a quasi-steady-state approach is expected

to be an adequate representation of the time-dependent problem. This

approach can be achieved through successive steady-state PIPEPHASE

simulations, each representing a time-step in the operating history of the

field.

The main components of the time-stepping analysis are:

Well Grouping

Reservoir Depletion

Facilities Planning

Well Grouping Each of the well completion zones in a gathering network from a specificformation or reservoir. The decline in the reservoir pressure with time

and the changes in the characteristics of the fluid produced are a functionof the total fluid volume produced form the reservoir. For the purposes of

these claculations, a well completion is associated with a reservoir

group. A reservoir group includes all of the producing zones that con-

tribute to its depletion.


99/101


ReservoirDepletion

The depletion of a reservoir over the life of a field is represented by a

decline in average reservoir pressure that affects the production capacity

of the associated wells. Additionally, with time, the composition of the

product fluid changes. For most reservoirs, the gas-oil ratio increases

with time; for a reservoir with an active water drive, the produced water

cut increases as the water table creeps up. The reservoir depletion featurewill predict the average decline in reservoir pressure for all the comple-

tions in the reservoir as a function of the cumulative produced volume.

In addition, at the end of every time step, it will update the water cut and

GOR in each associated completion zone as simplified functions of the

cumulative production rate (or reservoir pressure).

Figure 60:

Reservoir Pressure

Over Time

In PIPEPHASE, the user-specified data for reservoir depletion includes

the initial cumulative production rate (Qcum) and the basis for Qcumcal-culations. The default value for initial Qcumis zero (virgin field) and the

default calculation basis is oil (or gas for a gas field).

At every time step, PIPEPHASE calculates Q cumby adding production

from all the grouped wells. PIPEPHASE also calculates the change in

the average pressure, Pr, average, for the reservoir. It is important to notethat the initial value of the reservoir is taken to be the value you specified

in the Source dialog box. Subsequent values of P r are calculated from

Pr, average. This is a different case from the time-step calculations forfluid characteristics, water cut and GOR. In these cases, the initial values

are taken from the initial IPR curves rather than those specified in theSourcedialog box.

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100/101


WellDepletion

Production Ra te

The reservoir pressure declines by an amount calculated from the

grouped wells. This affects the IPR equation or the tabular data for the

IPR, since the reservoir pressure, Pr, is the common variable in most IPR

equations. Figure 61illustrates the dependence of production rate upon

wellhead pressure and reservoir pressure. As the reservoir pressuredeclines, so does cumulative production.

Figure 61:

Wellhead Pressure as

a Function of

Production Rate

Fluid Characteristics

For an active water drive reservoir, the water cut, fw, will increase signif-

icantly with increasing production. The data for the fwdecline curve can

be input in the IPR Decline Data dialog box. However, you must also

specify an initial value for fwin the input dialog box for the Source node.

Therefore, an ambiguity may exist between the IPR calculated value for

initial fwand that entered into the source data. To resolve any discrep-

ancy, PIPEPHASE will use the value calculated from the IPR curve.This data is well specific, and therefore, gives a more reliable value than

that input into the source node, which may be an average value.

Figure 62:

Water Cut and GOR

as a Functi on of

Production Rate

Similarly, for a Solution Gas Drive Reservoir, the Gas:Oil Ratio (GOR)

varies with increasing production. To properly model this time-depen-

dent variation, PIPEPHASE uses the values from the IPR decline curve

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(if you have supplied these). Otherwise, PIPEPHASE uses the initial

GOR value youve specified in the Source node.

In cases of enhanced oil recovery, PIPEPHASE allows you to specify

additional parameters to more accurately model the system. In the case

of pressure maintenance in an oil field, an additional well is used to

inject fluid (for example, water), into the reservoir to prevent or hinder

the decline of reservoir pressure. The cumulative production then

becomes a function of the amount of fluid being injected and the physi-

cal properties of that fluid.

(17)

injection well production well

If water is injected into an oil reservoir, a given volume of water will nothave the same pressure as an equivalent volume of oil. Therefore,

PIPEPHASE allows you to enter a Formation Volume Factor (FVF),

which takes into account the fluid properties. The FVF is represented by

B in the equation above. PIPEPHASE also allows you to specify a deliv-

erability basis for the calculations. The default basis is oil, and this is

indicated by the Boin the denominator within the summation above.

Qcum Qcum init ial,Bw

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