Steven W. Poston is a retired professor emeritus from Texas A&M University, with more than 18 years of teaching experience at the graduate and undergraduate levels in applied reservoir engineering analysis and subsurface description of petroleum reservoirs both in the United States and internationally. His industry experience includes more than 14 years in a variety of subsurface engineering, geological, and managerial roles for Gulf Oil Exploration and Production Company in Nigeria, Pennsylvania, Louisiana, and Texas. Poston has coauthored numerous industry technical papers, served on a number of SPE committees, and was coauthor of the SPE books Overpressured Gas Reservoirs, Analysis of Production Decline Curves, and Analysis of Oil and Gas Production Performance.
Marcelo Laprea-Bigott is a professor of engineering practice at the Harold Vance Department of Petroleum Engineering at Texas A&M University and has more than 45 years of consulting experience and an extensive background in developing and delivering technical training courses in the field of reservoir engineering for a variety of national oil companies and international clients. He joined Texas A&M University in 2006 after 20 years with Schlumberger Data and Consulting Services, having been an advisor in their Network of Excellence in Training (NExT). Laprea-Bigott’s other private sector industry experience includes more than 13 years as founder, principal owner, and president of Simupet, C.A., a petroleum engineering consulting firm; Consorcio Lamar C.A., an integrated oilfield tubulars management company; and president of S. A. Holditch and Associates–Venezuela. Additionally, he was a professor at Universidad de Oriente–Venezuela, a visiting adjunct professor at Texas A&M University, a visiting adjunct professor at the University of Tulsa, and the former assistant director of the Energy Institute at Texas A&M University. Laprea-Bigott holds a PhD degree from Texas A&M University. He is the coauthor of Analysis of Oil and Gas Production Performance.
Part 1 Introduction to Reservoir Analysis Principles 1
1 Reservoir Rocks and Framework 3
1.1 Reservoir Description 3
1.2 Log Shapes 6
1.3 Sedimentary Cycles 7
1.4 Log Correlation 9
1.4.1 Fence Diagrams 11
1.5 Geologic Maps 11
1.5.1 Counting Net Sand 12
1.5.2 Isopach Maps 12
1.5.3 Oil-in-Place 15
1.5.4 Gas-in-Place 15
1.6 Sediments 18
1.6.1 Carbonate Reservoir Rock 18
1.6.2 Clastic Reservoirs. 20
1.7 Clastic Depositional Environments 22
1.8 Reservoir Heterogeneity 23
1.9 Summary 27
1.10 Questions 27
1.11 Nomenclature 28
1.12 Problems 28
1.13 References 32
2 Reservoir Rock Properties 33
2.1 Porosity 34
2.2 Formation Compressibility 34
2.3 Permeability 37
2.3.1 Relation between Porosity and Permeability. 39
2.3.2 Darcy’s Law for Liquid Flow—Closed Outer Boundary
Conditions—Oilfield Units 39
2.3.3 Heterogeneous Flow Conditions 40
2.4 Fluid Distribution 41
2.4.1 Fluid Distribution and Capillary Mechanisms 41
2.5 Fluid Gradients and Reservoir Pressures 51
2.6 The J-Function 53
2.7 Fractional Flow Equation 55
2.7.1 Effective and Relative Permeability 55
2.7.2 Two-Phase Mobility 59
2.8 Summary 60
2.9 Questions 61
2.9.1 General Questions 61
2.9.2 Capillary Pressure and Relative Permeability Questions 61
2.9.3 Relative Permeability Questions 62
2.10 Nomenclature 62
2.11 References 64
3 Reservoir Fluid Properties 65
3.1 Hydrocarbon Mixtures 65
3.1.2 Phase Diagrams 66
3.1.3 Separators 68
3.2 Natural-Gas Properties 68
3.2.1 Critical Properties 69
3.2.2 Pseudoreduced Temperature and Pressure Coefficients 70
3.2.3 Single-Phase z-Factor 70
3.3 Gas Property Correlations 71
3.3.1 Piper-McCain-Corredor Correlations 71
3.3.2 Gas Formation Volume Factor 73
3.3.3 Gas Compressibility 74
3.4 Oil Properties 74
3.4.1 Specific Gravity 75
3.4.2 Viscocity 76
3.4.3 Gas/Oil Ratio 76
3.4.4 Oil Formation Volume Factor 77
3.5 Oil Property Correlations 78
3.5.1 Vasquez and Beggs Correlations 78
3.5.2 Standing Correlations 81
3.6 Water Properties 82
3.6.1 Water Composition 82
3.6.2 Diagrams 83
3.6.3 Potential Reactions 83
3.6.4 Oilfield Water Properties 84
3.7 Summary 86
3.8 Questions 86
3.9 Nomenclature 87
3.10 Problems 88
3.11 References 91
4 Well and Reservoir Models 93
4.1 Well and Reservoir Boundaries 94
4.1.1 Inner Boundary Condition 95
4.1.2 Outer Boundary Condition 95
4.2 Reservoir Pressure Responses 96
4.2.1 Constant pwf in a Well Completed in an Infinite Reservoir 96
4.2.2 Constant Rate for a Well Completed in an Infinite Reservoir 96
4.2.3 Constant pwf in a Well Completed in a Closed Reservoir 96
4.2.4 Constant-Rate Well Completed in a Closed Reservoir 97
4.2.5 Constant Outflow and Inflow Rates at Both Boundaries 97
4.3 Darcy Equation 97
4.3.1 Liquid Flow 98
4.3.2 Heterogeneous Flow Conditions 99
4.4 The Diffusivity Equation 103
4.4.1 Superposition 103
4.4.2 Dimensionless Time and Radius 105
4.4.3 Diffusivity Equation Solutions 105
4.4.4 Radius of Investigation 111
4.5 Summary 112
4.6 Questions 113
4.7 Nomenclature 113
4.8 Problems 114
4.9 References 115
5 Oil Reservoirs 117
5.1 Reservoir Depletion Mechanisms 118
5.1.1 Compressibility Effects 118
5.1.2 Undersaturated and Saturated Reservoirs 119
5.2 Oil Reservoir Types 120
5.3 Recovery Factors 120
5.3.1 Recovery as a Function of Drive Mechanism 121
5.3.2 Recovery as a Function of Residual Oil Saturation (Eq. 5.1) 122
5.3.3 Empirical Correlations To Estimate Reserves 122
5.4 Material-Balance Equation 123
5.5 Solution Procedure 126
5.5.1 Estimating OOIP 126
5.5.2 Method of Analysis 127
5.6 Field Example 129
5.6.1 The Material-Balance Study 130
5.6.2 Calculate Apparent Oil-in-Place 130
5.6.3 Calculate Water Influx as a Function of Time 131
5.6.4 Calculate Drive Indices as a Function of Time 132
5.7 Summary 134
5.8 Questions 134
5.9 Nomenclature 134
5.10 Problems 135
5.11 References 142
6 Inflow Performance 143
6.1 Calculating Choke Performance 143
6.1.1 Gilbert Method 145
6.1.2 The Poettmann and Beck Method 145
6.2 Productivity Index 148
6.2.1 Method Development 148
6.2.2 Productivity Index Plot 149
6.2.3 Calculating qmax from a Single-Phase Well Test 149
6.3 Inflow Performance below the Bubblepoint 151
6.3.1 The Vogel Equation 151
6.3.2 Fetkovich Method 154
6.4 Inflow Performance for Damaged Wells 156
6.4.1 Standing Method 156
6.4.2 Camacho-V. and Raghavan Method 158
6.5 Predicting Future Performance 159
6.5.1 Fetkovich Method 160
6.5.2 Relating Mobility to Pressure Change 161
6.5.3 Klins and Clark Method 162
6.6 Summary 165
6.7 Questions 166
6.8 Nomenclature 166
6.9 Problems 167
6.10 References 175
7 Water Influx 177
7.1 Aquifer Description 178
7.2 Mathematical Models 178
7.2.1 Schilthuis Method 178
7.2.2 van Everdingen and Hurst Solution 186
7.2.3 Carter and Tracy Method 193
7.2.4 Fetkovich Method 198
7.2.5 Comparison of Methods 203
7.3 Summary 204
7.4 Questions 205
7.5 Nomenclature 205
7.6 Problems 206
7.7 References 210
8 Displacement Concepts 211
8.1 Buckley-Leverett Frontal Advance 212
8.1.1 Development of the Fractional Flow Equation 213
8.1.2 The Shape of the Fractional Flow Curve 217
8.1.3 The Stabilized-Zone Concept 221
8.1.4 Balancing the Areas 221
8.1.5 The Saturation Profile 222
8.1.6 Secant Line 223
8.2 Stiles Method 229
8.3 Summary 235
8.4 Questions 236
8.5 Nomenclature 236
8.6 Problems 237
8.7 References 240
Part 2 Introduction to Waterflood Design 241
9 Waterflooding Process 243
9.1 The Secondary Recovery Process 243
9.1.1 Reservoir Depletion 243
9.2 Shale Layers and Disseminated Clays 246
9.2.1 Presence of Clay (Shale) 246
9.2.2 Effects of Shale Layers on Depletion 246
9.2.3 Edge Waterdrive vs. Bottom Waterdrive 247
9.2.4 Clays 247
9.3 Data Management—Available Information 249
9.3.1 Performance Histories 249
9.4 Reservoir Description 252
9.4.1 Maps and Cross Sections 252
9.4.2 OOIP and Reserves 253
9.5 Displacement Efficiency and Waterflood Patterns 255
9.5.1 Pattern Water Injection 255
9.5.2 Peripheral Water Injection 256
9.6 Summary 258
9.7 Questions 259
9.8 Nomenclature 260
9.9 References 260
10 Waterflood Components 261
10.1 Water Properties and Sources 261
10.2 Physical Plant 261
10.2.1 Water Sources and Handling 262
10.2.2 Water Treatment 263
10.2.3 Water Characterization 265
10.3 Injection-Well Design and Surveillance 267
10.3.1 Step-Rate Pressure Tests 268
10.4 Injection-Well Problems 270
10.5 Water-Injection Profiles 271
10.5.1 Well Analysis Using a Hall Plot 271
10.6 Summary 272
10.7 Questions 273
10.8 Nomenclature 274
10.9 References 274
Part 3 Field Study 275
11 Field Study—Analysis Workshop 277
11.1 Introduction 277
11.2 Field Study Overview 279
11.3 Process and Procedures 280
11.4 Field Study Tasks 281
11.4.1 Data File and Initial Character Review 281
11.4.2 Reservoir Evaluation 289
11.4.3 Project Plan 291
11.4.4 Well Considerations 292
11.4.5 Plant Requirements 293
11.5 Study Guide 293
11.5.1 Task 1—Study Maps, Log Profiles, and C1 Sand Continuity 294
11.5.2 Task 2—Study Log Profiles 294
11.5.3 Tasks 3, 4, and 5—Study Well History Profiles and General Reservoir and Field Information, and Plot a Corrected Static BHP Record 294
11.5.4 Task 6—Calculate Reservoir Volume, OOIP, and OGIP294
11.5.5 Task 7—Study Performance Records and Decline Curves To Predict Remaining Primary Recovery 295
11.5.6 Task 8—Determine Whether a Secondary Gas Cap Has Formed 296
11.5.7 Task 9—Apply the Fetkovich Method To Calculate Water-Influx History 296
11.5.8 Task 10—Apply Material-Balance Equation Technique 296
11.5.9 Tasks 11 and 12—Estimate Reserves 297
11.5.10 Task 13—Estimate Displacement Efficiency 298
11.5.11 Task 14—Calculate Remaining Primary and Secondary Recovery Reserves 299
11.5.12 Task 15—Apply the Stiles Calculations To Forecast Performance 299
11.5.13 Task 16—Evaluate Findings and Determine Waterflood Project Feasibility 301
11.5.14 Task 17—Calculate Water-Injection Requirements 301
11.5.15 Task 18—Estimate the Production Response to Water Injection 301
11.5.16 Task 19—Summarize the Status of the Wells 301
11.5.17 Task 20—Calculate Expected Hydrostatic Pressures 302
11.5.18 Task 21—Calculate Pressure Rating for Pump Pressure Gradient 303
11.5.19 Task 22—Calculate the Expected Pressure Response Resulting from an Expansion of the Flood Front 303
11.5.20 Task 23—Determine the Effects of Formation Damage on the Water-Injection Rate 303
11.5.21 Additional Considerations 304
11.6 Workshop Summary 305
11.7 Nomenclature 305
12 Results of Analysis 307
12.1 Tasks 1 and 2—Study Maps, Log Profiles, and C1 Sand Continuity 307
12.2 Tasks 3 and 4—Study Production Records, Well History Profiles and General Reservoir and Field Information 307
12.3 Task 5—Analyze Bottomhole Pressures 307
12.4 Task 6—Calculate Reservoir Volume, Original Oil-in-Place, and Original Gas-in-Place 308
12.5 Task 7—Study Performance Records and Decline Curves To Predict Remaining Primary Recovery 309
12.6 Task 8—Determine Whether a Secondary Gas Cap Has Formed 310
12.7 Task 9—Apply the Fetkovich Method To Calculate Water Influx 310
12.8 Task 10—Apply the Material-Balance Equation Technique 310
12.9 Tasks 11 and 12—Estimate Reserves 312
12.9.1 Task 11—Recovery as a Function of Residual Oil Saturation 312
12.9.2 Task 12—API Subcommittee on Recovery Efficiency (1967) Equations 313
12.10 Task 13—Estimate Displacement Efficiency 313
12.11 Task 14—Calculate Remaining Primary and Secondary Recovery Reserves 314
12.11.1 Recovery 314
12.11.2 Waterflood Reserves 314
12.12 Task 15—Apply the Stiles Calculations To Forecast Performance 315
12.13 Task 16—Determine Waterflood Project Feasibility 315
12.14 Task 17—Calculate Water-Injection Requirements 315
12.15 Task 18—Estimate the Production Response to Water Injection 316
12.16 Task 19—Analyze the Status of the Wells 317
12.17 Task 20—Calculate Expected Hydrostatic Pressures 318
12.18 Task 21—Calculate Pressure Rating for Pump Pressure Gradient 318
12.18.1 Initial Injection Pressure 318
12.19 Task 22—Calculate the Expected Pressure Response Resulting from an Expansion of the Flood Front 318
12.20 Task 23—Determine the Effects of Formation Damage on the Water-Injection Rate 319
12.20.1 Example Calculation 319
12.21 Additional Considerations 320
12.22 Summary 320
12.23 Nomenclature 321
13 Summary of Results 323
13.1 Reservoir Configuration 323
13.2 Production—Pressure History 323
13.3 Original Oil-in-Place 323
13.4 Reserves 323
13.4.1 Cautionary Notes. 323
13.5 Well Requirements 324
13.6 Water-Injection Requirements 324
13.7 Future Performance 324
14 Waterflood Review 325
14.1 Introduction 325
14.2 Waterflood Event 325
14.3 Monitoring Performance 327
14.4 Analysis and Causes of Poor Performance—Producing Wells 334
14.5 The Waterflooding Process—Summary 336
14.6 Nomenclature 337
References 339
Index 345