1. WELL TEST OBJECTIVES 1

1.2 Reservoir Evaluation 2

1.3 Reservoir Management 2

1.4 Reservoir Description 3

1.5 Decline Curve Analysis 3

1.6 Types of Tests 4

1.6.1 Drawdown Test 4

1.6.2 Buildup Test 5

1.6.3 Injection Test 5

1.6.4 Falloff Test 6

1.6.5 Interference Test 6

1.6.6 Drill Stem Test (DST) 7

1.7 References 7

2. WELL TEST CONCEPTS 9

2.2 Dimensionless Variables 10

2.3 The Skin Effect 12

2.3.1 Flow Efficiency 14

2.3.2 Partial Penetration Skin 15

2.4 Wellbore Storage 16

2.5 Infinite Acting Radial Flow 22

2.6 Semilog Analysis 24

2.6.1 Semilog Analysis -- Illustrative Example 25

2.7 Log-Log Type Curves 27

2.7.1 Type Curve Analysis -- Illustrative Example 28

2.8 Reservoir Boundary Response 30

2.8.1 Closed Boundaries 30

2.8.2 Fault Boundaries 33

2.8.3 Constant Pressure Boundaries 34

2.9 Radius of Investigation 35

2.10 Fractured Wells 36

2.10.1 Finite Conductivity Fractures 37

2.10.2 Infinite Conductivity Fractures 38

2.10.3 Uniform Flux Fracture 39

2.11 Dual Porosity Behavior 41

2.12 Summary of Responses in Time Sequence 44

2.13 Superposition 46

2.14 Time Superposition -- Multirate Tests 49

2.15 Buildup Tests 54

2.15.1 Buildup Tests -- Illustrative Example 58

2.15.2 Treating Buildups as Drawdowns 60

2.15.3 Average Reservoir Pressure 60

2.16 References 62

3. COMPUTER-AIDED ANALYSIS 65

3.2 Graphical Presentations 66

3.3 The Derivative Plot 67

3.3.1 Derivative Plots for Buildup Tests 76

3.3.2 Calculating Derivatives 79

3.3.3 Estimating Dual Porosity Parameters on Derivative Plots 82

3.4 Diagnostic Plot Evaluation 83

3.5 Data Preparation 84

3.5.1 Number and Frequency of Data 85

3.5.2 Datum Shifting 87

3.6 Nonlinear Regression 88

3.6.1 Confidence Intervals 89

3.6.2 Initial Pressure 93

3.6.3 Multirate and Variable Rate Tests 94

3.7 Desuperposition 97

3.8 Interpretation Sequence 101

3.9 Non-Ideality 102

3.10 References 104

4. GAS WELL TESTS 107

4.2 Real Gas Pseudopressure and Pseudotime 107

4.3 Calculating Pseudopressures 109

4.4 Using Normalized Pseudopressure for Analysis 111

4.5 Using Pseudopressure for Analysis 112

4.6 Rate Dependent Skin Effect 114

4.7 References 116

5. MULTIPHASE WELL TESTS 119

5.2 Perrine's Approach 121

5.3 Pressure Squared Approach 123

5.4 References 124

6. DESIGNING WELL TESTS 127

6.2 Variable Dependency 127

6.3 Test Duration 129

6.4 Flow Rate Considerations 130

7. ADVANCED TOPICS 133

7.1.1 Flow Regimes 133

7.1.2 Estimating Parameters 136

7.1.3 Nonlinear Regression 138

7.2 Multilayered Well Analysis 139

7.2.1 Tests without Flow Measurements 140

7.2.2 Tests with Flow Rate Measurement 142

7.3 References 142

8. WORKED EXAMPLES 145

8.1.1 Identifying Flow Periods 146

8.1.2 Estimating Parameters 147

8.1.3 Type Curve Match 148

8.1.4 Comparison of Graphical Estimates 150

8.1.5 Time Shift Errors 152

8.1.6 Pressure Shift Errors 154

8.1.7 Confidence Intervals 155

8.1.8 Nonlinear Regression 156

8.1.9 Radius of Investigation 159

8.1.10 Truncated Data 160

8.1.11 Simultaneous Rate-Pressure Data 162

8.2 Bounded Reservoir Example 165

8.2.1 Ambiguity 168

8.3 Buildup Test Example 170

8.3.1 Test Without Boundary Effects 170

8.3.2 Effects of Boundaries 173

8.3.3 Knowledge of pwf 175

8.4 Fractured Well Examples 176

8.4.1 Finite Conductivity Fracture Example 176

8.4.2 Infinite Conductivity Fracture Example 182

8.5 Dual Porosity Examples 186

8.5.1 Example with Modest Wellbore Storage 187

8.5.2 Example with Larger Wellbore Storage 189

8.5.3 Buildup Effects 191

8.6 Interference Test Examples 194

8.6.1 Single Flow Rate Example 194

8.6.2 Multirate Example 197

8.7 Gas Well Test Example 199

8.8 References 203

9. CALCULATING PROPERTIES 205

9.2 Oil Properties 205

9.3 Gas Properties 207

9.4 Water Properties 211

9.5 Rock Properties 212

9.6 Total Properties 213

9.7 References 214

10. FIELD EXAMPLES 217

Test 2: Channel Sand 220

Test 3: Closed Drainage Area 221

Test 4: Wedge Shaped Boundary 223

Test 5: Transition Data 224

Test 6: Horizontal Well 225

Test 7: Test from Mechanical Gauge 227

Test 8: Damaged Well 228

Test 9: Thermal Recovery Well 229

Test 10: Uninterpretable Test 229

Test 11: Horizontal Well 230

Test 12: Short Test 231

Test 13: Short Test 232

Test 14: Short Test 234

Test 15: Hydraulically Fractured Well 236

Test 16: Falloff Test with Prior Shut-In 238

Test 17: Gas Well Buildup 240

Test 18: Acidized Well 241

Test 19: Ambiguous Response 242

Test 20: Horizontal Well 245

Test 21: Downhole Flow Rate Measurement 246

Test 22: Damaged Well Buildup 249

Test 23: Hydraulically Fractured Well 251

Test 24: Dual Porosity Response 252

Test 25: Geothermal Well 253

References 254

Index 255