Oil Well Testing Handbook, 1st Edition

CHAPTER 1

Introduction

1.1 Role of Oil Well Tests and Information in Petroleum Industry

1.2 History of Oil Well Testing

1.3 Uses of Oil Well Tests

1.4 Oil Well Data Acquisition, Analysis and Management

Efficient Oil Well Test Analysis Programs

1.5 Selecting Oil Wells for Optimum Stimulation Treatment

1.6 Reservoir System Characterization Process

Most Common Oil Well Test Interpretation Methods

1.7 Scopes and Objective

1.8 Orginization

1.9 Units Systems and Conversions

References for Additional Reading

CHAPTER 2

Fundamentals of Reservoir Oil Flow Analysis

2.1 Introduction

2.2 Basic Fluid Flow Equations in Oil Reservoir

Steady-State Flow Equations and Their Practical Applications

Ideal Steady-State Flow Equations - Radial Flow

Pseudo-Steady-State Flow Equations

Flow Equations for Different Flow Regimes

Time to Reach Pseudo-Steady State

Unsteady-State (Transient) Flow Equations

Radial Diffusivity Equation

Various Dimensional Flow Geometry

2.3 Dimensionless Form of Flow Equations, Groups and Variables

2.4 Analytical Solutions of Fluid Flow Equations

Bounded (Finite) Cylindrical Reservoir

Infinite-Acting Reservoir With Line Source Well

Pseudo-Steady State Flow

Wellbore Storage Effects and Solutions

Flow Analysis in Generalized Reservoir Geometry

Wellbore Damage Analysis and Stimulation

Time and Radius of Investigation Equations

2.5 Application of Superposition Techniques

Effects of More Than One Well

Rate Change Effects

Pressure Change Effects

Simulation Boundary Effects

Use of Horner's Approximation

2.6 Numerical Models and Their Applications

Purpose and Objective of Reservoir Simulation

Reservoir Model Development Process

Selection of Numerical Simulation Models and Applications

2.7 Formulation and Numerical Solutions of Reservoir Simulation Equations

Single Phase Flow

Three Phase Oil-Gas-Water Flow

Two-Phase Oil-Gas Flow in Fractured Reservoir

2.8 Steady State and Semi-Steady State Pressure Distribution Calculations

2.9 Pressure Distribution Calculations Unsteady-State Conditions

Infinite External Boundary Conditions

Finite External Boundary Conditions

2.10 Unsteady-State Pressure Distribution Calculations in Directional Well

2.11 Summary

References for Additional Readings

CHAPTER 3

Transient Well Testing Methods For Horizontal Oil Wells

3.1 Introduction

3.2 Flow Equations for Horizontal Oil Wells

Steady State Flow Equations and Solutions

Unsteady State Equations and Solutions

Calculating Effective Wellbore Radius for Horizontal Oil Well

Effect of Formation Damage on Horizontal Well Productivity

Investigating Effect of Sv and b on Horizontal Well Productivity Ratio

Pseudo-Steady State Equations and Solutions

Shape Related Skin Factor for Vertical and Fractured Oil Wells

Shape Factors for Horizontal Oil Wells

Calculation of Skin Factor for Horizontal Oil Wells

Pseudo-Steady State Productivity Calculation Methods

3.3 Horizontal Oil Well Performance During Transient State

3.4 Transient Well Testing Techniques in Horizontal Oil Wells

Early Time Radial Flow Equation

Intermediate Time Linear Flow Equation

Late Time Radial Flow Equation

Late Time Linear Flow Equation

Possible Flow Regimes and Analytical Solutions

3.5 Flow Time Equations and Solutions

3.6 Pressure Response Equations and Methods of Analysis

Under Condition of Pressure Drawdown Test

Under Condition of Pressure Buildup Test

3.7 Horizontal Well Pressure and Normalized Pressure Derivative

3.8 Effects of Wellbore Storage

3.9 Summary

References for Additional Reading

CHAPTER 4

Pressure Drawdown Testing Techniques For Oil Wells

4.1 Introduction

4.2 Pressure Time History for Constant Rate Drawdown Test

4.3 Transient Analysis - Infinite Acting Reservoirs

4.4 Late Transient Analysis - Bounded (Developed) Reservoirs

4.5 Semi-Steady State Analysis - Reservoir Limit Test

4.6 Two-Rate Flow Test Analysis

When Initial Pressure is Not Known

When Initial Pressure is Known

4.7 Variable Rate Flow Tests

Modified Variable Rate Case

Transient Case

Average Reservoir Pressure Calculations

Semi-Steady State Case

4.8 Multi-Rate Flow Test Analysis

Multi-Rate, Single Phase Test

Multi Rate, Multi-Phase Test

4.9 Drawdown Rate Normalization Equations and Solutions

Analysis Methods, Their Applications and Limitations

Drawdown Rate Normalization Equations and Solutions

4.10 Summary

References for AdditionalReading

CHAPTER 5

Pressure Buildup Analysis Techniques For Oil Wells

5.1 Introduction

5.2 Ideal Pressure Buildup Test

5.3 Actual Buildup Test - Infinite Reservoir

5.4 Pressure Buildup Test Analysis - Infinite Acting Reservoir

Effects and Duration of After-Flow Test

Calculating Flow Capacity and Formation Permeability

Estimating Skin Factor

Pressure Drop Due to Skin

Determining Effective Wellbore Radius

Flow Efficiency and Damage Ratio

Estimating Skin Effects of Incompletely Perforated Interval

Determining Skin Effects in a Partially Completed Damaged Well

Estimating Reservoir Size from Two Pressure Buildup Tests

Typical Shapes of Buildup Curves

5.5 Pressure Buildup Testing Methods for Finite (Bounded) Reservoir

Horner and MBH Method

Miller-Dyes-Hutchinson (MDH) Method

Extended Muskat Method

Slider's Technique for Analyzing Buildup Test

5.6 Multiphase Buildup Test Analysis

5.7 Afterflow Analysis Using Russell's Techniques

5.8 Pressure Buildup Tests Proceeded by Two Different Flow Rates

5.9 Variable Rate Pressure Buildup Analysis

5.10 Multiphase Multirate Buildup Test Analysis

5.11 Rate Normalization Techniques and Procedures - Pressure Buildup Data

Analysis Methods, Their Uses and Limitations

Buildup Rate Normalization Equations and Solutions

Normalized Pressure Modified MDH Plot Analysis

Normalized Pressure Squarer Root Time plot

Average Reservoir Pressure Equation

5.12 Summary

References for AdditionaReading

CHAPTER 6

Original and Average Reservoir Pressure Estimation Methods

6.1 Introduction

6.2 Original Reservoir Pressure in Infinite Reservoirs

6.3 Estimating Average and Initial Pressure

Horner and MBH Method

MDH Method

Dietz Method

Ramey and Cobb Methods

Modified Muskat Method

Arps and Smith Method

6.4 Estimating Constant Pressure at Aquifer in Water Drive Reservoirs

Boundary and Average Pressure Estimating Methods

6.5 Summary

References for Additional Reading

CHAPTER 7

Well Testing Methods for Naturally Fractured Oil Reservoirs

7.1 Introduction

7.2 Identification of Natural Fractures

7.3 Characteristics of Naturally Fractured Reservoirs

7.4 Typical Pressure Drawdown Behavior Curve Shapes

7.5 Pressure Buildup Behavior Characteristics

7.6 Well Test Interpretation Methods, Uses and Limitations

Pseudo Steady-State Model

Transient State Model

Pressure Gradient Models

Type Curve Matching Technique

Pressure Derivative Method

7.7 Buildup Analysis Techniques For Tight Reservoir Matrix

7.8 Interpretation of Interference Tests in Matrix and Fractured Reservoirs

Uses of Interference Tests

Dimensionless Fracture Pressure Solution

Dimensionless Matrix Pressure Solution

Interference Test Analysis Using Type Curve Match Equations

7.9 Horizontal Well Pressure Behavior Curve Shapes

Identification of Various Flow Periods

Well Test Analysis Equations and Solutions

7.9 Horizontal Well Production Forecasting for Dual Porosity Reservoir

7.10 Summary

References for Additional Reading

CHAPTER 8

Fundamentals of Type Curve Matching Methods For Oil Wells

8.1 Introduction

8.2 Application to Conventional Tests

Ramey's Type Curves

Earlougher and Kersch Type Curves

McKinley's Type Curves

8.3 Fracture Type Curve Matching Techniques

Type Curves - Vertical Fractured Oil Wells

8.4 Types Curves - Horizontal Fractured Oil Wells

Using Pressure Drawdown Data

Estimation of Upper Limit of Permeability Thickness Product

8.5 Summary

References for Additional Reading

CHAPTER 9

Flow Regime Identification and Analysis Using Special Methods

9.1 Introduction

9.2 Fracture Linear Flow Period

9.3 Bilinear Flow

9.4 Formation Linear Flow

9.5 Pseudo-Radial Flow

9.6 Type Curve Matching Methods - Field Case Studies

Case 1 - Bilinear Flow Type of Analysis

Case 2 - Pressure Data Partially Match Curve for the Pseudo-Radial Flow Period

Case 3 - Pressure Exhibit a Half Slope Line on a Log-Log Plot

Case 4 - Pressure Data Partially Falling in the Pseudo-Radial Flow Period

9.7 Summary

References for Additional Reading

CHAPTER 10

Applications of Pressure Derivative in Oil Well Test Analysis

10.1 Introduction

10.2 Determining Pressure Derivative Functions

10.3 Log-Log Pressure and Pressure Derivative Diagnostic Plots

10.4 Pressure Derivative Trends For Other Common Flow Regimes

10.5 Pressure Derivative Applications to Well Test Analysis

10.6 Pressure derivative Analysis Methods

Pressure Buildup Test Data Matching Procedure

Pressure Drawdown Test Data Matching Procedures

10.7 Fractured Reservoir Systems

Pseudo-State Interporosity Flow

Transient Interporosity Flow

10.8 Summary

References for Additional Reading

CHAPTER 11

Massive Hydraulic Fractured Oil Well Behavior Analysis

11.1 Introduction

11.2 Methods of Evaluating MHF Fractured Oil Wells

11.3 Analyzing Infinite Flow Capacity Fractures

11.4 Analyzing Finite Flow Capacity Fractures

Constant Wellbore Pressure Case

Constant Rate Case

11.5 Estimating Formation Characteristics - Finite Conductivity Vertical Fractures

Curve Matching Procedures

Conventional Method of Analysis

11.6 Pretreatment Testing of Hydraulically Fractured Candidate

Horner Analysis

Linear Flow Analysis - High Conductivity Fractures

Type Curve Analysis

Bilinear Flow Analysis - Low Conductivity Fractures

11.7 Summary

References for Additional Reading

CHAPTER 12

Drill-Stem Testing Methods

12.1 Introduction

12.2 DST Equipment and Operational Procedures

Basics of DST Operations

DST Pressure Behavior

12.3 Recommended Flow and Shut-in Time for Drill-Stem Tests

12.4 Trouble Shooting DST Pressure Charts 444

DST Charts for Barrier Detection

12.5 Checking Validity and Consistency of Reported DST Data

12.6 Estimating Average Flow Rate

12.7 DST Analysis Methods, Uses and Their Limitations

Horner's Plot Method

Type Curve Matching Methods

Correa and Ramey's Method

Drill-Stem Buildup Test Analysis With Limited Data

12.8 Wireline Formation Test Data Evaluation

Open-Hole Formation Test

Closed-Hole Formation Test

Empirical Interpretation Charts for Formation Tester Results

Reservoir Rock's Porosity Distribution System Analysis

Matrix Pore Volume Calculation

Fracture Pore Volume Calculation

Partitioning Coefficient Estimation

Well Skin Effects

12.9 Summary

References for Additional Reading

CHAPTER 13

Oil Well Potential Evaluation and IPR Relationships

13.1 Introduction

13.2 Classification and Identifying Values of Permeability-Thickness Product

13.3 Isochronal and Flow After-Flow Tests

13.4 Wellbore Restriction Analysis

Procedure and Method of Analysis Well Test

Effect of Changing Completion Zone on Well IPR

13.5 Factors Affecting IPR Curves

13.6 Criteria for Identifying Type of Drives

13.7 Classifications to Predict IPR Curves

13.8 Basic Assumptions to Predict IPR Curves

13.9 Well Inflow Performance Calculation Methods for Vertical Oil Wells

From Limited Information

Single Phase Liquid and Two Phase Flow

When Flow Efficiency Not Equal to One

Two Phase Flow Producing Water

13.10 Inflow Performance (IPR) Relationship

Solution Gas Drive - Vertical and Horizontal Oil Wells

13.11 Development Procedure for Preparation of Future IPR Curves

IPR Calculating for Future Conditions

13.12 Summary

References for Additional Reading

CHAPTER 14

Interference and Pulse Testing and Analysis Methods

14.1 Introduction

14.2 Interference Test Analysis Techniques

Interference Test Analysis by Type Curve Matching

14.3 Analysis of Pulse Test Pressure Response

Characteristics of Pressure Response

Pulse Test Responses With Flow and Shut-in Time

Pulse Test Analysis Methods

Horizontal Pulse Test Analysis

14.4 Vertical Pulse Test Design and Analysis Methods

Vertical Pulse Test Design Calculations

14.5 Design and Analysis of Unequal Pulses

Pulse Test Designing Methods

Pulse Test Analysis Methods

14.6 Summary

References for Additional Reading

CHAPTER 15

Injection Well Transient Testing and Analysis

15.1 Introduction

15.2 Injectivity Test Analysis Methods

Under Steady State Conditions

Waterflood Reservoir With M.R =1

Liquid Filled Unit-Mobility-Ratio Reservoirs

15.3 Pressure Fall-off Test Analysis Methods

Liquid Filled Unit-Mobility-Ratio Reservoirs

Prior to Reservoir Fillup (Unit Mobility Ratio)

Prior to Reservoir Fillup (Non Unit Mobility Ratio)

15.4 Two Rate Injection Test Analysis

15.5 Step Rate Injectivity Testing Techniques

Estimation of Formation Fracture Pressure

15.6 Summary

References for Additional Reading

CHAPTER 16

Well Testing Methods in Multilayered Oil Reservoir Systems

16.1 Introduction

16.2 Identification of Layered Oil Reservoir Systems

16.3 Analyzing Pressure Behavior Multilayered Systems

Layered Reservoir With Crossflow

Layered Reservoir Without Crossflow

Composite Reservoirs

Interlayer Crossflow Reservoirs

16.4 Concept of Reservoir Layer Fracture Conductivity

16.5 Pressure-Production Performance Response Equations

Constant Producing Pressure

Constant Producing Rate

16.6 Investigating Degree of Communication and Type of Crossflow

16.7 Pressure Buildup Response Characteristics in Layered Reservoir Systems

16.8 Pressure Analysis Methods for Oil Wells Producing Commingled Zones

Conventional Analysis Method (Horner Plot)

MDH Method

Extended Muskat Plot

Other Methods

16.9 Factors Effecting Multilayered Reservoir Performance

16.10 Economic Aspects of Interlayer Crossflow 595

References for additional reading

CHAPTER 17

Pressure Analysis Methods in Heterogeneous Oil Reservoir Systems

17.1 Introduction

17.2 Effect of Pressure on Rock Properties

17.3 Major Causes of Heterogeneities

17.4 Pressure Responses Near No Flow Boundaries

Methods of Estimating Distance to a Linear Discontinuity

17.5 Effect of Hydraulic Diffusivity on Reservoir Behavior

17.6 Simple Procedures and Guidelines to Determine Reservoir Heterogeneity Properties

17.7 Simple Approach to Estimate Fracture Trends or Heterogeneities

17.8 Determination of Reservoir Parameters and Fracture Orientation

17.9 Defining Reservoir Heterogeneity By Multiple Well Testing Techniques

Homogeneous Isotropic Reservoir Systems

Anisotropic Reservoir Systems

Heterogeneous Reservoir Systems

17.10 Method for Calculating Fracture Orientation

17.11 Estimating Two Dimensional Permeability With Vertical Interference Testing

17.12 Application of Pulse Tests to Describe Reservoir Heterogeneity

Homogeneous Isotropic Reservoir Systems

Anisitropic Reservoir Systems

17.13 Validity of Various Models and Steps to Obtain Reservoir Descriptions

17.14 Summary

References for Additional Reading

CHAPTER 18

Oil Well Testing - Field Case Studies

18.1 Introduction

18.2 Oil Well Test Evaluation Sheet

18.3 Method to Convert Bottom Hole Pressure at Instrument Depth To Reservoir Datum

18.4 Determining Average Depth of Oil Reservoirs

18.5 Stimulation Efforts Evaluation, Summary and Results

Low Pressure Reservoirs -Multiphase Pressure Buildup Test Analysis

Field Case Studies

18.6 Transient Pressure Drawdown Test Analysis

General Equations

Method of Analysis

Field Case Studies

18.7 Skin Effect, Skin Factor, and Flow Efficiency

Positive (+) and Negative (-) Skins

Skin Factor Equations and Their Relationships

Causes of Positive and Negative Skins

Relationships With Flow Efficiency

18.8 Factors Responsible For Reduction in Formation Permeability

18.9 Improvement Analysis As a Result of Fracture Treatment

References for Additional Reading

CHAPTER 19

Decline Curve Analysis Methods

19.1 Introduction

19.2 Transient Decline Behavior Analysis

Transient Drainage Radius During Infinite-Acting Period

Characteristics of Exponent b During Transient Period

Production Characteristics During Transient Period

Constant Pressure Rate Decline

Constant Rate Production, Pressure Declining

19.3 Pseudo-Steady State Decline

Forecasting Rate Decline

19.4 Characteristics and Classification of Production Decline Curves

Hyperbolic Decline Behavior

Exponential Decline Behavior

Harmonic Decline Behavior

Characteristics and Decline Exponent b Estimating Techniques

Harmonic Decline Curve

19.5 Decline Response Behavior in Fractured Reservoirs

Classifications and Limitations of Log Log Type Curves

Type Curve Matching Methods

19.6 Summary

References for Additional Reading

CHAPTER 20

Overall Skin Effects and Impact On Oil Well Performance

20.1 Introduction

20.2 Concept of Skin Factor

20.3 Wellbore Damage Effects

20.4 Effective Wellbore Radius Concepts and Productivity Index Calculation Techniques

Vertical Wells

Horizontal Wells

20.5 Skin Factor Due to Partial Penetration

20.6 Skin Factor Due to Perforation

20.7 Skin from Partial Completion and Slant

20.8 Skin Factor Due to Reduced Crushed Zone Permeability

20.9 Slant Well Damage Skin Effect on Well Productivity

20.10 Horizontal Well Damage Skin Effects

Impact of Skin Effect on Horizontal Oil Well Performance

20.21 Summary

References for Additional Reading

APPENDIX A

Conversion Factors Between Unit Systems

APPENDIX B

Correlation Tables and Charts for Dimensionless Functions

References for Additional Readings

APPENDIX C

Pressure Drop Through Vertical, Inclined and Horizontal Oil Wells

C.1 Hagedorn and Brown Method - Vertical Oil Wells

C.2 Beggs and Brill Method - Inclined and Horizontal Pipes

References for Additional Readings

APPENDIX D

Oil and Water PVT Properties and Correlation Equations

D.1 Oil PVT Properties and Correlations

Bubble Point (Saturation) Pressure

Factors Affecting Saturation Pressure

Correlations For Saturation Pressure Calculation

D.2 Solution Gas Oil Ratio

D.3 Oil Formation Volume Factor (FVF)

Correlations to Determine Oil FVF

D.4 Total Formation Volume Fcator

D.5 Oil Density

D.6 Oil Viscosity

Factors Affecting Oil Viscosity

Methods to Estimate Oil Viscosity

D.7 Oil Compressibility

D.8 Reservoir Rock Properties

D.9 Reservoir PVT Water Properties

Use of New Tables to Determine Formation Water PVT Properties

References for Additional Readings

APPENDIX E

Substantial Set of Problems Without Solution

E.1 Routine exercises to Practical Applications

Nomenclature 7

Bibliography

Subject Index