MBAL Complete

Petroleum Experts

MBAL

Version 10.5January 2010

User Manual

IPM

MBALIPM - Analytical Reservoir Model OVERVIEW

by Petroleum Experts Limited

The MBAL package contains the classical reservoir engineering tool, which is part of theIntegrated Production Modelling Toolkit (IPM) of Petroleum Experts.

MBAL has redefined the use of Material Balance in modern reservoir engineering. MBALhas many innovations developed by Petroleum Experts that are not available elsewhere.

MBAL is the industry standard for accurate Material Balance modelling. Efficient reservoirdevelopments require a good understanding of reservoir and production systems. MBALhelps the engineer define reservoir drive mechanisms and hydrocarbon volumes moreeasily. This is a prerequisite for reliable simulation studies.

For existing reservoirs, MBAL provides extensive matching facilities. Realistic productionprofiles can be run for reservoirs, with or without history matching. The intuitive programstructure enables the reservoir engineer to achieve reliable results quickly. MBAL iscommonly used for modelling the dynamic reservoir effects prior to building a numericalsimulator model.

APPLICATIONS History matching reservoir performance to identify hydrocarbons in place and aquiferdrive mechanisms Building Multi-Tank reservoir model Generate production profiles Run development studies Determine gas contract DCQs Model performance of retrograde condensate reservoirs for depletionand re-cycling Decline curve analysis Monte Carlo simulations 1D flood front modelling Calibrate relative permeability curves against field performance data Control Miscibility Control recycling of injection gas Fully Compositional MBALs logical and progressive path leads the engineer through history matching areservoir and generating production profiles. The program is easy to use and fast to learn MBAL allows the engineer to tune PVT correlations to match with fielddata. This prevents data errors being compounded between modelling steps MBALs menu system minimises data entry by selecting only data relevant to thecalculation options selected

The copyright in this manual and the associated computer program are the property of Petroleum ExpertsLtd. All rights reserved. Both, this manual and the computer program have been provided pursuant to aLicence Agreement containing restriction of use.

No part of this manual may be reproduced, transmitted, transcribed, stored in a retrieval system, ortranslated into any language, in any form or by any means, electronic, mechanical, magnetic, optical orotherwise, or disclose to third parties without prior written consent from Petroleum Experts Ltd., PetexHouse, 10 Logie Mill, Edinburgh, EH7 4HG, Scotland, UK.

Petroleum Experts Ltd. All rights reserved.

IPM Suite, GAP, PROSPER, MBAL, PVTP, REVEAL, RESOLVE, IFM and OpenServer are trademarks ofPetroleum Experts Ltd.

Microsoft (Windows), Windows (2000) and Windows (XP) are registered trademarks of the MicrosoftCorporation

The software described in this manual is furnished under a licence agreement. The software may be usedor copied only in accordance with the terms of the agreement. It is against the law to copy the software onany medium except as specifically allowed in the license agreement. No part of this documentation may bereproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying,recording, or information storage and retrieval systems for any purpose other than the purchaser's personaluse, unless express written consent has been given by Petroleum Experts Limited.

Address:

Petroleum Experts LimitedPetex House10 Logie MillEdinburgh, ScotlandEH7 4HG

Tel : (44 131) 474 7030Fax : (44 131) 474 7031

email: [email protected]: www.petex.com

Copyright Notice

3

1990-2010 Petroleum Experts Limited

MBALI

Table of Contents0

Chapter 1 Technical Overview 2................................................................................................................................... 31 Material Balance ................................................................................................................................... 62 Reservoir Allocation ................................................................................................................................... 73 Monte Carlo ................................................................................................................................... 84 Decline Curve Analysis ................................................................................................................................... 95 1D Model

................................................................................................................................... 106 Multilayer

................................................................................................................................... 117 Tight Gas Type Curves

................................................................................................................................... 128 What's New

Chapter 2 User Guide 25................................................................................................................................... 261 Getting Help

.......................................................................................................................................................... 27Accessing Help ................................................................................................................................... 272 Using the MBAL application

.......................................................................................................................................................... 27File Management ......................................................................................................................................................... 28Opening and Saving Files......................................................................................................................................................... 29Append......................................................................................................................................................... 30Defining the Working Directory......................................................................................................................................................... 30Preferences......................................................................................................................................................... 33Viewing the Software Key......................................................................................................................................................... 33Selecting Printers and Plotters......................................................................................................................................................... 33Windows Notepad.......................................................................................................................................................... 33Setting the Units ......................................................................................................................................................... 34Defining System Units......................................................................................................................................................... 34Defining the Global Unit System......................................................................................................................................................... 35Changing individual variable units......................................................................................................................................................... 36Minimum and Maximum Limits......................................................................................................................................................... 37Conversion Details......................................................................................................................................................... 38Resetting the Units......................................................................................................................................................... 38Generating a Units Report.......................................................................................................................................................... 38MBAL Command Buttons

................................................................................................................................... 393 Data Input and Import .......................................................................................................................................................... 40Importing Data in MBAL ......................................................................................................................................................... 41Importing an ASCII File

......................................................................................................................................... 43Static Filter......................................................................................................................................................... 43Import Set-up......................................................................................................................................................... 45Line Filter......................................................................................................................................................... 46Import Filter......................................................................................................................................................... 48Plots, Reports

......................................................................................................................................... 48The Plot Screen................................................................................................................................... 50Variables................................................................................................................................... 51Leaving the plot screen................................................................................................................................... 51Resizing the display

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MBAL HelpJanuary, 2010

................................................................................................................................... 51Modifying the plot display

................................................................................................................................... 51Plot scales

................................................................................................................................... 53Display menu

................................................................................................................................... 53Labels

................................................................................................................................... 54Colours

................................................................................................................................... 56Plot line widths

................................................................................................................................... 56Fonts

................................................................................................................................... 57Plot Legends......................................................................................................................................... 57Output

................................................................................................................................... 57Selecting a printer or plotter

................................................................................................................................... 58Making a hard copy of the plot......................................................................................................................................... 58Changing the plotted variables......................................................................................................................................... 59Reporting

................................................................................................................................... 59Selecting sections to include in the report

................................................................................................................................... 62Solving printing problems......................................................................................................................................................... 63Importing data from an ODBC Datasource

......................................................................................................................................... 64Filter Set-up......................................................................................................................................................... 65Choose Table & Fields.......................................................................................................................................................... 65Static Import Filter .......................................................................................................................................................... 66Defining the system ......................................................................................................................................................... 67Reservoir Analysis Tools......................................................................................................................................................... 68System options

......................................................................................................................................... 69Tool options

......................................................................................................................................... 69User information

......................................................................................................................................... 69User comments and date stamp.......................................................................................................................................................... 69Describing the PVT ......................................................................................................................................................... 71Selecting the PVT method......................................................................................................................................................... 73Black Oil PVT Descriptions

......................................................................................................................................... 73PVT Command buttons

......................................................................................................................................... 74PVT for Oil................................................................................................................................... 76Two stage separator

......................................................................................................................................... 80Controlled Miscibility Option

......................................................................................................................................... 81Matching PVT correlations

......................................................................................................................................... 82Matching correlations

......................................................................................................................................... 87Using PVT tables

......................................................................................................................................... 89PVT Tables for Controlled Miscibility

......................................................................................................................................... 92Variable PVT for Oil Reservoir

......................................................................................................................................... 96PVT for Gas

......................................................................................................................................... 99Water Vapour Option......................................................................................................................................... 100PVT for Retrograde Condensate......................................................................................................................................... 103Black Oil Condensate model validation procedure......................................................................................................................................... 112PVT for General Model......................................................................................................................................... 114Multiple PVT Definitions......................................................................................................................................... 116Checking the PVT calculations

......................................................................................................................................................... 120Compositional Modelling......................................................................................................................................... 121EOS Model Setup

................................................................................................................................... 122EOS Model

................................................................................................................................... 123Optimisation Mode

................................................................................................................................... 124Separator Calc Method

................................................................................................................................... 126Injection Gas Source......................................................................................................................................... 127Compositional Tracking......................................................................................................................................... 132Fully Compositional fluid description

................................................................................................................................... 134Lumping/Delumping

................................................................................................................................... 1364 The Material Balance Tool

MBALIII

.......................................................................................................................................................... 137Material Balance Tank Model ......................................................................................................................................................... 140Recommended Workflow.......................................................................................................................................................... 141MBAL Graphical Interface ......................................................................................................................................................... 141Manipulating Objects......................................................................................................................................................... 146Viewing Objects......................................................................................................................................................... 147Validating Object Data.......................................................................................................................................................... 149Tool Options .......................................................................................................................................................... 152Input ......................................................................................................................................................... 153Wells Data

......................................................................................................................................... 153Setup

......................................................................................................................................... 155Production / Injection History

......................................................................................................................................... 156Well Production History

......................................................................................................................................... 158Production Allocation

......................................................................................................................................... 159Relative Permeability......................................................................................................................................................... 161Tank Input Data

......................................................................................................................................... 161Tank Parameters................................................................................................................................... 165Coalbed Methane Overview................................................................................................................................... 168Langmuir Isotherm Editor................................................................................................................................... 171Langmuir Isothem Calculation................................................................................................................................... 172Langmuir Isothem Plot................................................................................................................................... 172Langmuir Isothem Original................................................................................................................................... 173Coal Permeability Variation Model

......................................................................................................................................... 174Water Influx

......................................................................................................................................... 176Rock Compressibility

......................................................................................................................................... 178Rock Compaction

......................................................................................................................................... 180Pore Volume vs. Depth

......................................................................................................................................... 184Relative Permeability / Fractional Flow Tables................................................................................................................................... 186Relative Permeability Hysteresis................................................................................................................................... 187Calculate Tables from Corey Functions................................................................................................................................... 187Fractional Flow Tables

......................................................................................................................................... 189Entering the Tank Production History................................................................................................................................... 192Production History Comment................................................................................................................................... 193Production History layout

......................................................................................................................................... 193Production History

......................................................................................................................................... 193Calculating the Tank Production History and Pressure

......................................................................................................................................... 195Calculating the Tank Production History Rate Only

......................................................................................................................................... 195Plotting Tank Production History

......................................................................................................................................... 195Production Allocation......................................................................................................................................................... 196Transmissibility Data

......................................................................................................................................... 197Transmissibility Parameters

......................................................................................................................................... 200Transmissibility Production History

......................................................................................................................................... 202Transmissibility Matching......................................................................................................................................................... 203Transfer from Reservoir Allocation......................................................................................................................................................... 204Input Summary......................................................................................................................................................... 204Input Reports.......................................................................................................................................................... 205History Matching ......................................................................................................................................................... 206History Setup......................................................................................................................................................... 207Analytical Method

......................................................................................................................................... 211Regressing on Production History

......................................................................................................................................... 213History Points Sampling

......................................................................................................................................... 214Changing the Weighting of History Points in the Regression......................................................................................................................................................... 216Graphical Method

......................................................................................................................................... 218Changing the Reservoir and Aquifer Parameters

......................................................................................................................................... 219Straight Line Tool

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......................................................................................................................................... 220Locating the Straight Line Tool

......................................................................................................................................... 220Graphical method results

......................................................................................................................................... 220Abnormally pressured gas reservoirs......................................................................................................................................................... 222Energy Plot......................................................................................................................................................... 223WD Function Plot......................................................................................................................................................... 224Simulation......................................................................................................................................................... 230Fw / Fg / Fo Matching

......................................................................................................................................... 233Running a Fractional Flow Matching......................................................................................................................................................... 236Sensitivity Analysis

......................................................................................................................................... 236Running a Sensitivity.......................................................................................................................................................... 237Production Prediction ......................................................................................................................................................... 238Production Prediction Overview......................................................................................................................................................... 243Prediction Setup......................................................................................................................................................... 252Production and Constraints

......................................................................................................................................... 257Voidage Replacement and Injection......................................................................................................................................................... 257Breakthrough Saturations......................................................................................................................................................... 258DCQ Swing Factor (Gas reservoirs only)......................................................................................................................................................... 259DCQ Schedule......................................................................................................................................................... 261Well Type Definitions

......................................................................................................................................... 262Well Type Setup

......................................................................................................................................... 263Well Inflow Performance

......................................................................................................................................... 266More Well Inflow Performance

......................................................................................................................................... 268Inflow Performance (IPR) Models

......................................................................................................................................... 272Gravel Pack Model

......................................................................................................................................... 274Multirate Inflow Performance

......................................................................................................................................... 276Gas and Water Coning Matching................................................................................................................................... 276Gas Coning Matching................................................................................................................................... 277Water Coning Matching

......................................................................................................................................... 279Well Outflow Performance

......................................................................................................................................... 281Tubing Performance................................................................................................................................... 281Constant Bottom Hole pressure................................................................................................................................... 282Tubing Performance Curves................................................................................................................................... 284Importing Tubing Performance Curve data................................................................................................................................... 285Cullender Smith correlation................................................................................................................................... 287Witley correlation

......................................................................................................................................................... 288Testing the Well Performance

......................................................................................................................................................... 289The Fixed Well Schedule

......................................................................................................................................................... 291Potential Well Schedule

......................................................................................................................................................... 291The Reporting Schedule

......................................................................................................................................................... 293Running a Prediction......................................................................................................................................... 294Saving Prediction Results......................................................................................................................................... 296Plotting a Production Prediction

......................................................................................................................................................... 297Displaying the Tank Results

......................................................................................................................................................... 297Displaying the Well Results

......................................................................................................................................................... 299Production Prediction Reports

................................................................................................................................... 2995 Reservoir Allocation Tool .......................................................................................................................................................... 299Background .......................................................................................................................................................... 302Reservoir Allocation Tool Capabilities .......................................................................................................................................................... 302Graphical Interface .......................................................................................................................................................... 303Tool Options .......................................................................................................................................................... 304Input Data ......................................................................................................................................................... 304Tank Input Data......................................................................................................................................................... 306Well Input Data......................................................................................................................................................... 307Transfer from Material Balance

MBALV

.......................................................................................................................................................... 307Calculations ......................................................................................................................................................... 308Setup......................................................................................................................................................... 308Run Allocation......................................................................................................................................................... 310Tank Results......................................................................................................................................................... 311Well/Layer Results

................................................................................................................................... 3136 Monte-Carlo Technique .......................................................................................................................................................... 313Program Functions .......................................................................................................................................................... 313Technical Background .......................................................................................................................................................... 315Tool Options .......................................................................................................................................................... 317Distributions

................................................................................................................................... 3197 Decline Curve Analysis .......................................................................................................................................................... 320Tool Options .......................................................................................................................................................... 321Programme Functions .......................................................................................................................................................... 322Production History .......................................................................................................................................................... 325Matching the Decline Curve .......................................................................................................................................................... 328Prediction Set-up .......................................................................................................................................................... 329Reporting Schedule .......................................................................................................................................................... 329Running a Production Prediction

................................................................................................................................... 3308 1D Model .......................................................................................................................................................... 3301D model options .......................................................................................................................................................... 332Program Functions .......................................................................................................................................................... 332Technical Background ......................................................................................................................................................... 333Simultaneous Flow......................................................................................................................................................... 333Fractional Flow.......................................................................................................................................................... 334Reservoir and Fluids Properties .......................................................................................................................................................... 336Relative Permeability .......................................................................................................................................................... 337Running a Simulation ......................................................................................................................................................... 339Plotting a Simulation

................................................................................................................................... 3399 Multi Layer Tool .......................................................................................................................................................... 339Programme Functions .......................................................................................................................................................... 340Technical Background .......................................................................................................................................................... 342Tool Options .......................................................................................................................................................... 343Reservoir parameters .......................................................................................................................................................... 344Layer Properties ......................................................................................................................................................... 345Relative Permeability.......................................................................................................................................................... 346Running a Calculation .......................................................................................................................................................... 347Fw/Fg Matching

................................................................................................................................... 34910 Tight Gas Type Curve Tool .......................................................................................................................................................... 349Background .......................................................................................................................................................... 350Tight Gas Tool Options .......................................................................................................................................................... 351Input ......................................................................................................................................................... 351Well Data: conventional reservoir

......................................................................................................................................... 353Tight Gas Well Data Setup

......................................................................................................................................... 354Tight Gas Well Data Production History

......................................................................................................................................... 356Tight Gas Well Data Outflow Performance......................................................................................................................................................... 356Tight Gas Input Data Report

......................................................................................................................................... 357Tight Gas Well Input Data Report.......................................................................................................................................................... 359History Matching ......................................................................................................................................................... 360Tight Gas History Setup......................................................................................................................................................... 360Tight Gas History Type Curve Plot......................................................................................................................................................... 362Tight Gas History PD Plot......................................................................................................................................................... 362Tight Gas History Simulation Plot

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......................................................................................................................................................... 362Tight Gas History P/Z Plot

......................................................................................................................................................... 363Tight Gas History Fetkovich-McCray Plot

......................................................................................................................................................... 364Tight Gas History McCray Integral Plot

......................................................................................................................................................... 364Tight Gas History Simulation

......................................................................................................................................................... 364Tight Gas History Simulation Plot

......................................................................................................................................................... 364Tight Gas History Report

......................................................................................................................................................... 365Tight Gas History Agarwal-Gardner.......................................................................................................................................................... 366Tight Gas Prediction ......................................................................................................................................................... 367Tight Gas Prediction Setup......................................................................................................................................................... 368Tight Gas Prediction Constraints......................................................................................................................................................... 369Tight Gas Prediction......................................................................................................................................................... 369Tight Gas Prediction Plot......................................................................................................................................................... 369Tight Gas Prediction Report

................................................................................................................................... 36911 Appendix .......................................................................................................................................................... 369A - References .......................................................................................................................................................... 371B - MBAL Equations ......................................................................................................................................................... 371Material Balance Equations

......................................................................................................................................... 371PVT................................................................................................................................... 371Gas Equivalent

......................................................................................................................................... 372OIL

......................................................................................................................................... 373GAS

......................................................................................................................................... 373Graphical History Matching Methods: Oil................................................................................................................................... 373Havlena - Odeh................................................................................................................................... 374F/Et versus We/Et................................................................................................................................... 374(F - We)/Et versus F (Campbell)................................................................................................................................... 374(F - We) versus Et................................................................................................................................... 375(F - We) / (Eo + Efw) versus Eg / (Eo + Efw)................................................................................................................................... 375F / Et versus F (Campbell - No Aquifer)

......................................................................................................................................... 375Graphical History Matching Methods: Gas................................................................................................................................... 375P/Z................................................................................................................................... 376P/Z (Overpressured)................................................................................................................................... 376Havlena Odeh (Overpressured)................................................................................................................................... 377Havlena & Odeh (water drive)................................................................................................................................... 377Cole ((F-We)/Et)................................................................................................................................... 377Roach (unknown Compressibility)................................................................................................................................... 378Cole - No Aquifer (F/Et)

......................................................................................................................................... 378Reservoir Voidage......................................................................................................................................................... 379Aquifer Models

......................................................................................................................................... 379Small Pot

......................................................................................................................................... 379Schilthuis Steady State

......................................................................................................................................... 380Hurst Steady State

......................................................................................................................................... 381Hurst-van Everdingen-Dake

......................................................................................................................................... 384Hurst-van Everdingen-Odeh

......................................................................................................................................... 384Vogt-Wang

......................................................................................................................................... 385Fetkovitch Semi Steady State

......................................................................................................................................... 387Fetkovitch Steady State

......................................................................................................................................... 387Hurst-van Everdingen Modified

......................................................................................................................................... 390Carter-Tracy......................................................................................................................................................... 390Relative Permeability

......................................................................................................................................... 391Corey Relative Permeability Function

......................................................................................................................................... 391Stone method 1 modification to the Relative Permeability Function

......................................................................................................................................... 391Stone method 2 modification to the Relative Permeability Function......................................................................................................................................................... 392Nomenclature

......................................................................................................................................... 394Subscripts

MBALVII

.......................................................................................................................................................... 394C - Fluid Contacts Calculation details ......................................................................................................................................................... 394D-1 Pore Volume vs. Depth......................................................................................................................................................... 399D-2 Standard Fluid Contact Calculations......................................................................................................................................................... 404D-3 Trapped Saturation Fluid Contact Calculations......................................................................................................................................................... 409D-4 Trapped Saturation Fluid Contact Calculations.......................................................................................................................................................... 411D- Trouble Shooting Guide ......................................................................................................................................................... 412E-1 Prediction not Meeting Constraints......................................................................................................................................................... 412E-2 Production Prediction Fails......................................................................................................................................................... 412E-3 Pressures in the Prediction are increasing (With No Injection)......................................................................................................................................................... 413E-4 Reversal in the Analytic Plot......................................................................................................................................................... 413E-5 Difference between History Simulation and Analytic Plot......................................................................................................................................................... 414E-6 Dialogues Are Not Displayed Correctly

Chapter 3 Examples Guide 416................................................................................................................................... 4161 Quick Start Guide on Material Balance tool

.......................................................................................................................................................... 416Data Available

.......................................................................................................................................................... 417Setting up the Basic Model

.......................................................................................................................................................... 422Matching to Production History data in MBAL ......................................................................................................................................................... 427Using Simulation Option to Quality Check the History Matched Model.......................................................................................................................................................... 428Forecasting ......................................................................................................................................................... 429Rel Perm Matching......................................................................................................................................................... 430Confirming the validity of the rel perms......................................................................................................................................................... 436Predicting reservoir pressure decline without a well......................................................................................................................................................... 439Predicting production and reservoir pressure decline with a well model......................................................................................................................................................... 452Predicting number of wells to achieve target rate

................................................................................................................................... 4542 Water Drive Oil Reservoir .......................................................................................................................................................... 455Starting the Model .......................................................................................................................................................... 456PVT Menu .......................................................................................................................................................... 459Reservoir Input .......................................................................................................................................................... 460Rock Properties .......................................................................................................................................................... 460Relative Permeability .......................................................................................................................................................... 461Production History .......................................................................................................................................................... 461History Matching .......................................................................................................................................................... 467Well by Well History Matching .......................................................................................................................................................... 486Multitank modelling

................................................................................................................................... 4993 Coalbed Methane Material Balance .......................................................................................................................................................... 502Starting the Model .......................................................................................................................................................... 502PVT Menu .......................................................................................................................................................... 503Reservoir Input .......................................................................................................................................................... 505Rock Properties .......................................................................................................................................................... 505Relative Permeability .......................................................................................................................................................... 506Prediction

................................................................................................................................... 5174 Tight Gas Example .......................................................................................................................................................... 518PVT Definition .......................................................................................................................................................... 519Input Well Data .......................................................................................................................................................... 521History Matching .......................................................................................................................................................... 529Prediction

................................................................................................................................... 5325 Other Example Files

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Chapter

1

Technical Overview 2


1 Technical Overview

PETROLEUM EXPERTS MBAL is a reservoir modelling tool belonging to the IPM suite.This tool was designed to allow for greater understanding of the current reservoir behaviourand perform predictions while determining its depletion. Reservoir modelling can be carried out within MBAL with the use of several different tools tofocus on different aspects:

Material Balance, Reservoir Allocation Monte Carlo volumetrics, Decline Curve Analysis, 1-D Model (Buckley-Leverett) Multi-Layer (relative permeability averaging) Tight Gas Type Curve tool

Each of the available tools and the methods available for the fluid behaviour modelling aredefined below.

3MBAL Help January, 2010

MBAL

1.1 Material Balance

The material balance concept is based on the principle of the conservation of mass:

Mass of fluids originally in place = Fluids produced + Remaining fluids in place.

This can be synthesized in the fundamental equation:

where: F is the productionEt is the expansion term, depending on PVT and reservoir parametersWe is the water influx term

The material balance program uses a conceptual model of the reservoir to predict thereservoir behaviour based on the effects of reservoir fluids production and gas to waterinjection.

The material balance equation is zero-dimensional, meaning that it is based on a tank modeland does not take into account the geometry of the reservoir, the drainage areas, theposition and orientation of the wells, etc.

However, the material balance approach can be a very useful tool in performing many tasks,some of which are highlighted below:

Quantify different parameters of a reservoir such as hydrocarbon in place, gas cap size,etc.

Determine the presence, the type and size of an aquifer, encroachment angle, etc. Estimate the depth of the Gas/Oil, Water/Oil, Gas/Water contacts. Predict the reservoir pressure for a given production and/or injection schedule, Predict the reservoir performance and manifold back pressures for a given production

schedule. Predict the reservoir performance and well production for a given manifold pressure

schedule.

Fluid PVT ModelingMBAL allows to model any type of reservoir fluids: Oil, Dry and Wet gas, RetrogradeCondensate. A General type of fluid allows the user to define independent PVT models forthe oil and the gas in equilibrium, modeling in this way gas bubbling out of the oil andcondensate dropping out of the gas.

The fluid behaviour when material balance is in use can be modelled with the use of threeavailable methods:

Black Oil The parameters used within material balance to define the fluid andphase behavior (Bo, Bg, GOR etc.) are calculated and entered into



Correlations material balanceEquation of State

The use of an equation of state to define the phase and composition ofthe fluid across the entire system

Tracking In essence, this is a combination of Black Oil correlations and EOS.The black oil correlations are used to model the pressure dropcalculations across the system and equation of state is then applied todetermine the composition at given points in the system by performingcompositional blends and flashes. This is a unique capabilitypossessed by MBAL which ensures that the produced fluid GOR canbe recombined to match to the initial fluid composition

Greater detail for each method and its applicability for different fluids (oil, gas or retrogradecondensate) are defined under Describing the PVT .

High relief reservoirsThe fluid PVT can be considered homogenous within the reservoir, or variable with depth tomodel PVT properties varying with depth within high relief reservoirs.

Multiple tanksThe reservoir structure can be modeled with a unique tank or with multiple tanks connectedby means of transmissibilities. This option is useful in cases of compelx reservoir geologythat cannot be simplified to a simple homogenous tank.

History MatchingMBAL is renown in the industry as the state of the art material balance modeling and historymatching tool. Several history matching methods can be used to match, cross check andquality check the model against past production history.These are the main method available. Each method may have sub-methods that will bedescribed in further chapters

Graphical method

This consists of rearranging the material balance equation inopportune ways in order to achieve plots with special properties

Analytical method

This consists of calculating the main phase production (for example,oil) on the basis of the historical reservoir pressure variation andhistory of production of the secondary phases (for example gas,water), and then comparing the model results with the productionhistory of pressure and main phase production

Energy Plot This consists of a qualitative plot that is able to quickly identify themain drive mechanisms in the reservoir

Wd function plot

This consist of a dimensionless plot of water influx vs time describingthe aquifer response over time

Production history data can be defined for the total reservoir or for each well producing.

Coalbed methane (NEW!!!)

IPM 7.5 is released with a major development in MBAL: Coalbed Methane. Two options are

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MBAL

available to model coalbed methane in MBAL: using the classical material balance tool orinside the tight gas type curves tool when the production is expected to show significanttransience.



1.2 Reservoir Allocation

When a well is producing from multiple layers, it is essential for an engineer to know howmuch each layer has contributed to the total production. Traditionally, this reservoir allocationhas been done based on the kh of each layer. This approach does not take the IPR of the layers into account and also ignores the rate ofdepletion of the layers. The Reservoir Allocation tool in MBAL improves the allocation by allowing the user to enterIPRs for each layer and calculates the allocation by taking the rate of depletion into accountas well. Crossflow is also accounted for in the model, as well as different start/finish times forthe wells. Impurities are also tracked and can provide an effective measure of the quality ofthe underlying assumptions in the case where few data is available.

This system can be used to define the historical production from each layer for oil, gas orretrograde condensate.


MBAL

1.3 Monte Carlo

The Monte-Carlo technique is used to evaluate the hydrocarbons in place. Each of theparameters involved in the calculation of reserves, basically the PVT properties and the porevolume, are represented by statistical distributions.

Depending on the number of cases (NC) chosen by the user, the program generates aseries of NC values of equal probability for each of the parameters used in the hydrocarbonsin place calculation. The NC values of each parameter are then cross-multiplied creating adistribution of values for the hydrocarbons in place. The results are presented in the form ofa histogram.

We link the probability of Swc and porosity to reflect physical reality. If the porosity is nearthe bottom of the probability range, the Swc will be weighted to be more likely to be near thebottom of the range. Similarly if the porosity is near the top of the range, the Swc will beweighted to be near the top of the range. The same method is used to link the GOR and oilgravity.

Oil, gas or retrograde condensates can be modelled within this system.



1.4 Decline Curve Analysis

This tool analyses the decline of production of a well or reservoir versus time. It uses thehyperbolic decline curves described by Fetkovich based on the equation:

( )tabi aiq

q D+ -= **11

where:q is the production rate,qi is the initial production rate,a is the hyperbolic decline

exponent,bi is the initial decline rate,t is the time.

Curves can be matched to reproduce past history of production, or entered directly in themodel.

The program also supports production rate 'breaks' or discontinuities. These breaks can beattributed to well stimulation, change of completion, etc.

Oil, gas or retrograde condensates can be modelled while using this method.


MBAL

1.5 1D Model

This tool allows the study of the displacement of oil by water or gas, using the fractional flowand Buckley-Leverett equations. The model does not presuppose any displacement theory.

The model assumes the following: The reservoir is a rectangular box, with an injector well at one end and a producer at

the other. The production and injection wells are considered to be perforated across the entire

formation thickness. The injection rate is constant. The fluids are immiscible. The displacement is considered as incompressible. The saturation distribution is uniform across the width of the reservoir. Linear flow lines are assumed, even in the vicinity of the wells. Capillary pressures are neglected.

As this method is used to model the displacement of oil, this is only fluid which can bemodelled using this tool.



1.6 Multilayer

The purpose of this tool is to generate pseudo relative permeability curves for multi-layerreservoirs using immiscible displacement. These can then be used by other tools in MBALsuch as Material Balance.A single PVT description can be entered. A single pressure and temperature is entered forthe reservoir which is used to calculate the required fluid properties.Each layer has its own set of relative permeabilitys, thickness, porosity and permeability.The model considers the incline of the reservoir in all calculation types apart from Stilesmethod.The steps include:

Specify the injection phase (gas or water) Specify the calculation type; Buckley-Leverett, Stiles, Communicating Layers or

Simple. Enter the PVT description. Enter reservoir description Enter the layer description Calculate the production profile for each layer and combine all the layers into a

consolidated production profile. Since we are only interested in the relative layerresponse, we use a dimensionless model wherever possible (e.g. length=1 foot andinjection rate =1 cf/d).

Calculate a pseudo relative permeability curve for the reservoir using the Fw/Fgmatch plot.

If required the pseudo-layer calculated from the multi-layers created by the above steps canthen be reused as a single layer in a new model. For example a pseudo-layer calculatedfrom a communicating multi-layer model can be used as input for a single layer Buckley-Leverett model. Or one could even run two different multi-layer communicating models anduse the two pseudo-layers as input to a multi-layer Buckley-Leverett model.

Either oil or gas can be modelled within this system, while water or gas can also be used asthe injection fluid.

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MBAL Help January, 2010

MBAL

1.7 Tight Gas Type Curves

In cases where Material Balance is not applicable because of long transience periods, thistool can provide a good alternative for history matching and forecasting. It is based on welltesting theory and incorporates a number of plots that can assist with history matching thesetype of reservoirs. As implied by the title, this model focuses on gas alone to analyse thebottom hole pressure data from individual wells.

Further detail and examples of the uses for the above models is available throughout thisdocument.

This document explains the basic procedures to follow in order to set-up a MBAL modelusing the examples provided. This user guide focuses on how to use the various programfeatures as analytical tools to solve engineering problems. The section titled 'Example Guide'contains worked examples and the appendix gives a list of the references for the variousmodels implemented in the MBAL software package. Users of this software will be able tofind even greater detail if referring to the references defined in the Appendix.



1.8 What's NewVersion 10.5

MBAL Version 10.5 - Enhancements Implemented:

Coal Bed Methane

Option added to material balance tanks and tight gas wells to allow modelling ofcoabed methane reservoirs using Langmuir isotherms to determine how much gas isdesorbed from the rock surface and released into pore space

Version 10.0


Tight Gas Model

Agarwal-Gardner Type-curve matching for tight gas tool

Also implemented for tight gas tool to allow modelling of WGR

Fractional Flow

Look-up table for fractional flow instead of relative permeability curves

Control of regression variables for fractional flow matching

Compositional Lumping/Delumping

Production History

Import multiple well production history

Entry of production history by month or year

Undo facility in history matching

Plotting of prediction well rates against history well rates

PVT

New Al-Marhoun PVT correlation for Pb, Rs & Bo

Miscellaneous

Handle gas-lift curves with casing head pressure

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MBAL

Ability to change units in dialog

Allow edit/view of well relative permeability (prior to import to GAP)

Plot IPR with and without gravel pack

Version 9.0


New Tight Gas Tool

Allows analysis of transient reservoirs for gas only.

Material Balance Tool

Correct IPR for the effect of gravel pack

Prediction based on Production Schedule for Multi-tanks.

Extend prediction type 1 (from production schedule) to multi-tank cases

Prediction to Calculate Minimum Number of Wells to achieve Target Rate.

Improvements to Production History Input

Enter comment for each history point and display on plots

Display weighting in production history dialogue

Improvements on Graphical Plot

Campbell & Cole plot without aquifer

Best line fit over selected range of points

Option to try various line fits before committing to tank data.

Check Valve on Transmissibilities

Calculate the GOR etc in History Simulation from Rel Perms and Saturations

Accept All Fits button on Analytic Plot Regression.

Version 8.0




Production Allocation Tool

Impurity Tracking Track CO2, N2 and H2S to allow comparison with measured values.

Allow transmissibilities Model transmissibilities to connect tanks..

Material Balance Tool Full Compositional Model Completely new model to perform molar balance in tanks instead of material balance Uses fluid properties calculated from compositional models for IPR and VLP well

calculations

New Contact Calculation New method added for oil tanks to model residual gas saturation trapped in the oil zone.

Rock Compaction Model New model to allow comparison with reservoir simulators.

New Open Server Commands Perform allocation of well production. Run regression calculations in history matching. New commands to allow models to be created from scratch. Import PVT file into PVT dataset

New water producer well types (including ESP, HSP and PCP) Allow oil and gas wells to produce from water tanks Downhole pore volume reported in the simulation/prediction Simulation/Prediction plots have option to plot all streams in different colours

All Tools

Plotting improvements Number of grid blocks is now configurable. Scales can be saved on several plot types.

Table Input Grids Cut/Copy/Paste/Clear available for selected rows and columns.

Minimum calculation unit reduced to 1 second Previously the smallest time unit was one day Calculations can now be performed down to one second To do this, the data unit in the units system needs to be altered to something other than

calendar date setting e.g hours, seconds or date/time

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MBAL

Version 7.0


Production Allocation Tool New tool to calculate layer rates when only total well rates are available.

Material Balance

Water vapour correction for gas Option to model the water vapour in the gas. Can be used in gas, condensate and general

fluid options

Water Coning Option to model water coning in oil tanks.

Gas injection gravity modelled in history matching Gas injection gravity can now be entered in the tank history. It is then taken into account

in the history matchingoptions

Two-phase Relative Permeability Plots Option to plot relative permeability curves in traditional two-phase layout.

Relative Permeability Inflow Correction for Gas Add ability to correct the inflow performance for changes in relative permeability for gas

and condensate wells.

- Abnormally Pressured Reservoir Method - A new method for analyzing gas reservoirs.

Maximum DCQ constraint A constraint has been added to allow a maximum DCQ to be set when using the

prediction type that calculates a DCQ.

Relative Permeability Hysteresis An option is now available to model hysteresis for relative permeability curves.

New contact calculation method to include trapped saturations New method for calculating fluid contact calculations that include trapped phases. Results column layouts are retained after new calculations.

New option to calculate system rate constraints on instantaneous rates In previous versions MBal always calculated the system constraints on average rates. Definition of Pore Volume vs Depth table has been changed. For oil tanks, top of gas cap

is now always PV = -1. For condensate tanks, bottom of oil leg is now PV = 2. See Porevolume vs Depth for more information.



- Option to display file name in hard copy of plots

Generalised Material Balance Gas injected into tanks can now flow through transmissibilities into other tanks Separate manifolds are now available for producers from the oil leg and gas cap. Rates

are reported for each manifold as well as the total production rates Constraints can be applied to each manifold. Alternatively the oil leg and gas cap

producers can share a common manifold Impurities and compositions (both originally in the tank and injected) are now tracked

through transmissibilities and crossflow Added Fayers and Mathews method to calculate combined Sor for Stones 1 Relative

Permeability model Pb calculation available on tank parameters tab Copy PVT tables to match data or match data to tables. Also copy from one PVT object to

another Added gas-oil contact depth as a layer abandonment for gas coning In the Reporting Schedule, any number of dates can be entered in the User Date List

Version 6.5


Improved Multi-layer Tool Improved multi-layer tool to perform Stiles, Buckley-Leverett and Communicating layers

models.

Material Balance Populate rel perm tables from Corey table New option to calculate relative permeability tables from Corey exponents

Reference time All times can be displayed in days, weeks, months or years from a reference date

Cf defined as tangent The rock compressibility referenced back to initial pressure can be calculated from the

rock compressibility entered as a tangent

Separate rel perms for mobility correction A separate set of relative permeability tables can be entered and used only for the various

mobility corrections for the PI

Breakthroughs per tank For prediction type 1 (pressure from production schedule), phase breakthroughs can now

be entered

Allow single tank name to be edited.

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MBAL

All Tools

Plotting improvements These include configurable fonts on screen, new defaults colours with white background,

different colour scheme for screen and hard copy

Version 6.0


Material Balance

Generalised Material Balance New option to model a tank containing either initial oil, condensate or both. Also allows

control of re-production of injected gas

Controlled miscibility New option in the PVT section to allow re-dissolving of gas back into the oil to be

controlled

PVT per Tank New option to allow a different PVT dataset to be assigned to different tanks. Note that

when fluid moves from one tank to another the fluid is considered to have 'changed' intothe fluid in the target tank

Append File Option to read tanks, wells etc from a file and append them to MBAL without destroying

the current data

Enhanced Open Server Predictions can now be run step by step. Selected input data can be changed during the

prediction such as manifold pressure, PI etc

Variable PVT Datum A datum other than the initial GOC can be entered for the variable PVT option

Variable PVT with Multi-tank The variable PVT option can now be used with the multi-tank option. Different variable

PVT inputs can be used for different tanks

Calculate Rate Only Option to calculate rate only in consolidation of production history from different wells

Correct Vogel IPR rel perm correction option which includes the reduction of the Kro and Krw due to the

gas saturation

Plot Line Widths



Allow line widths to be set on plots

Export PVT Files The PVT data can be exported to a PVT file that can be read by PROSPER

Removed Prediction Type 2 Calculation of manifold pressure from production schedule Added option to history setup to use transmissibility rates in the graphical plots.

All Tools Conversion to 32 bit

Version 5.0


Material BalanceCompositional Tracking MBAL can now track a composition through a simulation or prediction

Oil breakthroughs Oil breakthroughs are now available for condensate wells

Relative Permeability Curves for Transmissibilities Relative permeability curves can now be assigned to a transmiss

Documents

MBAL Complete