Contents
Preface xvii
Acknowledgments xix
1 An Overview of Well Logging 1
1.1 Introduction 1
1.2 What is Logging? 2
1.2.1 What is Wireline Logging? 2
1.2.2 What is LWD? 5
1.3 Properties of Reservoir Rocks 7
1.4 Well Logging: The Narrow View 8
1.5 Measurement Techniques 10
1.6 How is Logging Viewed by Others? 11
References 15
2 Introduction toWell Log Interpretation:
Finding the Hydrocarbon 17
2.1 Introduction 17
2.2 Rudimentary Interpretation Principles 17
2.3 The Borehole Environment 21
2.4 Reading a Log 25
2.5 Examples of Curve Behavior and Log Display 29
2.6 A Sample Rapid Interpretation 33
References 37
Problems 38
3 Basic Resistivity and Spontaneous Potential 41
3.1 Introduction 41
3.2 The Concept of Bulk Resistivity 42
3.3 Electrical Properties of Rocks and Brines 46
3.4 Spontaneous Potential 49
3.5 Log Example of the SP 56
References 58
Problems 59
vii
viii CONTENTS
4 Empiricism: The Cornerstone of Interpretation 63
4.1 Introduction 63
4.2 Early Electric Log Interpretation 64
4.3 Empirical Approaches to Interpretation 66
4.3.1 Formation Factor 66
4.3.2 Archie’s Synthesis 69
4.4 A Note of Caution 71
4.4.1 The Porosity Exponent, m 71
4.4.2 The Saturation Exponent, n 72
4.4.3 Effect of Clay 74
4.4.4 Alternative Models 75
4.5 A Review of Electrostatics 77
4.6 A Thought Experiment for a Logging Application 78
4.7 Anisotropy 82
References 85
Problems 87
5 Resistivity: Electrode Devices and How They Evolved 91
5.1 Introduction 91
5.2 Unfocused Devices 91
5.2.1 The Short Normal 91
5.2.2 Estimating the Borehole Size Effect 94
5.3 Focused Devices 99
5.3.1 Laterolog Principle 99
5.3.2 Spherical Focusing 104
5.3.3 The Dual Laterolog 107
5.3.4 Dual Laterolog Example 110
5.4 Further Developments 114
5.4.1 Reference Electrodes 114
5.4.2 Thin Beds and Invasion 117
5.4.3 Array Tools 118
References 121
Problems 122
6 Other Electrode and Toroid Devices 125
6.1 Introduction 125
6.2 Microelectrode Devices 126
6.3 Uses for Rxo 129
CONTENTS ix
6.4 Azimuthal Measurements 133
6.5 Resistivity Measurements While Drilling 135
6.5.1 Resistivity at the Bit 135
6.5.2 Ring and Button Measurements 138
6.5.3 RAB Response 140
6.5.4 Azimuthal Measurements 142
6.6 Cased-Hole Resistivity Measurements 142
References 145
Problems 147
7 Resistivity: Induction Devices 149
7.1 Introduction 149
7.2 Review of Magnetostatics and Induction 150
7.2.1 Magnetic Field from a Current Loop 150
7.2.2 Vertical Magnetic Field from a Small Current Loop 152
7.2.3 Voltage Induced in a Coil by a Magnetic Field 154
7.3 The Two-Coil Induction Device 155
7.4 Geometric Factor for the Two-coil Sonde 157
7.5 Focusing the Two-coil Sonde 161
7.6 Skin Effect 164
7.7 Two-Coil Sonde with Skin Effect 166
7.8 Multicoil Induction Devices 167
7.9 Induction or Electrode? 171
7.10 Induction Log Example 174
References 176
Problems 177
8 Multi-Array and Triaxial Induction Devices 179
8.1 Introduction 179
8.2 Phasor Induction 180
8.2.1 Inverse Filtering 183
8.3 High Resolution Induction 185
8.4 Multi-Array Inductions 186
8.4.1 Multi-Array Devices 188
8.4.2 Multi-Array Processing 189
8.4.3 Limitations of Resolution Enhancement 192
8.4.4 Radial and 2D Inversion 194
8.4.5 Dipping Beds 197
x CONTENTS
8.5 Multicomponent Induction Tools and Anisotropy 200
8.5.1 Response of Coplanar Coils 200
8.5.2 Multicomponent Devices 205
References 208
Problems 211
9 Propagation Measurements 213
9.1 Introduction 213
9.2 Characterizing Dielectrics 214
9.2.1 Microscopic Properties 216
9.2.2 Interfacial Polarization and the Dielectric Properties of
Rocks 219
9.3 Propagation in Conductive Dielectric Materials 222
9.4 Dielectric Mixing Laws 224
9.5 The Measurement of Formation Dielectric Properties 228
9.6 2 MHz Measurements 231
9.6.1 Derivation of the Field Logs 231
9.6.2 General Environmental Factors 234
9.6.3 Vertical and Radial Response 235
9.6.4 Dip and Anisotropy 236
9.6.5 Array Propagation Measurements and their Interpretation 238
References 242
Problems 244
10 Basic Nuclear Physics for Logging Applications: Gamma Rays 247
10.1 Introduction 247
10.2 Nuclear Radiation 248
10.3 Radioactive Decay and Statistics 249
10.4 Radiation Interactions 251
10.5 Fundamentals of Gamma Ray Interactions 253
10.6 Attenuation of Gamma Rays 257
10.7 Gamma Ray Detectors 259
10.7.1 Gas-Discharge Counters 259
10.7.2 Scintillation Detectors 260
10.7.3 Semiconductor Detectors 264
References 264
Problems 265
CONTENTS xi
11 Gamma Ray Devices 267
11.1 Introduction 267
11.2 Sources of Natural Radioactivity 268
11.3 Gamma Ray Devices 271
11.4 Uses of the Gamma Ray Measurement 273
11.5 Spectral Gamma Ray Logging 275
11.5.1 Spectral Stripping 280
11.6 Developments in Spectral Gamma Ray Logging 283
11.7 A Note on Depth of Investigation 285
References 286
Problems 288
12 Gamma Ray Scattering and Absorption Measurements 289
12.1 Introduction 289
12.2 Density and Gamma Ray Attenuation 290
12.2.1 Density Measurement Technique 293
12.2.2 Density Compensation 296
12.3 Lithology Logging 300
12.3.1 Photoelectric Absorption and Lithology 300
12.3.2 Pe Measurement Technique 304
12.3.3 Interpretation of Pe 307
12.4 Inversion of Forward Models with Multidetector Tools 312
12.5 LWD Density Devices 312
12.6 Environmental Effects 314
12.7 Estimating Porosity from Density Measurements 317
12.7.1 Interpretation Parameters 318
References 321
Problems 322
13 Basic Neutron Physics for Logging Applications 325
13.1 Introduction 325
13.2 Fundamental Neutron Interactions 326
13.3 Nuclear Reactions and Neutron Sources 332
13.4 Useful Bulk Parameters 333
13.4.1 Macroscopic Cross Sections 333
13.4.2 Lethargy and Average Energy Loss 335
13.4.3 Number of Collisions to Slow Down 336
13.4.4 Characteristic Lengths 337
13.4.5 Characteristic Times 344
xii CONTENTS
13.5 Neutron Detectors 345
References 347
Problems 348
14 Neutron Porosity Devices 351
14.1 Introduction 351
14.2 Use of Neutron Porosity Devices 353
14.3 Types of Neutron Tools 353
14.4 Basis of Measurement 354
14.5 Historical Measurement Technique 358
14.6 A Generic Thermal Neutron Tool 361
14.7 Typical Log Presentation 364
14.8 Environmental Effects 366
14.8.1 Introduction to Correction Charts 367
14.9 Major Perturbations of Neutron Porosity 370
14.9.1 Lithology Effect 370
14.9.2 Shale Effect 372
14.9.3 Gas Effect 373
14.10 Depth of Investigation 374
14.11 LWD Neutron Porosity Devices 378
14.12 Summary 379
References 379
Problems 381
15 Pulsed Neutron Devices and Spectroscopy 383
15.1 Introduction 383
15.2 Thermal Neutron Die-Away Logging 384
15.2.1 Thermal Neutron Capture 384
15.2.2 Measurement Technique 386
15.2.3 Instrumentation 390
15.2.4 Interpretation 392
15.3 Pulsed Neutron Spectroscopy 395
15.3.1 Evolution of Measurement Technique 400
15.4 Pulsed Neutron Porosity 405
15.5 Spectroscopy 408
References 410
Problems 413
CONTENTS xiii
16 Nuclear Magnetic Logging 415
16.1 Introduction 415
16.1.1 Nuclear Resonance Magnetometers 416
16.1.2 Why Nuclear Magnetic Logging? 417
16.2 A Look at Magnetic Gyroscopes 418
16.2.1 The Precession of Atomic Magnets 419
16.2.2 Paramagnetism of Bulk Materials 421
16.3 Some Details of Nuclear Induction 423
16.3.1 Longitudinal Relaxation, T1 424
16.3.2 Rotating Frame 427
16.3.3 Pulsing 429
16.3.4 Transverse Relaxation, T2, and Spin Dephasing 430
16.3.5 Spin Echoes 431
16.3.6 Relaxation and Diffusion in Magnetic Gradients 432
16.3.7 Measurement Sensitivity 434
16.4 NMR Properties of Bulk Fluids 436
16.4.1 Hydrogen Index 436
16.4.2 Bulk Relaxation in Water and Hydrocarbons 437
16.4.3 Viscosity Correlations for Crude Oils 440
16.5 NMR Relaxation in Porous Media 442
16.5.1 Surface Interactions 443
16.5.2 Pore Size Distribution 446
16.5.3 Diffusion Restriction 448
16.5.4 Internal Magnetic Gradients 449
16.6 Operation of a First Generation Nuclear Magnetic Logging Tool 449
16.7 The NMR Renaissance of “Inside-Out” Devices 452
16.7.1 A New Approach 452
16.7.2 Numar/Halliburton MRIL 454
16.7.3 Schlumberger CMR and Subsequent Developments 455
16.7.4 LWD Devices 458
16.8 Applications and Log Examples 459
16.8.1 Tool Planners 459
16.8.2 Porosity and Free-Fluid Porosity 460
16.8.3 Pore Size Distribution and Permeability Estimation 463
16.8.4 Fluid Typing 465
16.9 Summary 471
xiv CONTENTS
16.10 Appendix A: Diffusion 472
References 473
Problems 477
17 Introduction to Acoustic Logging 479
17.1 Introduction to Acoustic Logging 479
17.2 Short History of Acoustic Measurements
in Boreholes 480
17.3 Applications of Borehole Acoustic Logging 482
17.4 Review of Elastic Properties 483
17.5 Wave Propagation 489
17.6 Rudimentary Acoustic Logging 493
17.7 Rudimentary Acoustic Interpretation 494
References 496
Problems 497
18 Acoustic Waves in Porous Rocks and Boreholes 499
18.1 Introduction 499
18.2 A Review of Laboratory Measurements 500
18.3 Porolelastic Models of Rocks 509
18.4 The Promise of Vp/Vs 513
18.4.1 Lithology 513
18.4.2 Gas Detection and Quantification 515
18.4.3 Mechanical Properties 517
18.4.4 Seismic Applications (AVO) 518
18.5 Acoustic Waves in Boreholes 519
18.5.1 Borehole Flexural Waves 524
18.5.2 Stoneley Waves 525
References 527
Problems 529
19 Acoustic Logging Methods 531
19.1 Introduction 531
19.2 Transducers – Transmitters and Receivers 532
19.3 Traditional Sonic Logging 534
19.3.1 Some Typical Problems 540
19.3.2 Long Spacing Sonic 541
19.4 Evolution of Acoustic Devices 544
19.4.1 Arrays of Detectors 546
CONTENTS xv
19.4.2 Dipole Tools 547
19.4.3 Shear Wave Anisotropy and Crossed Dipole Tools 549
19.4.4 LWD 553
19.4.5 Modeling-driven Tool Design 553
19.5 Acoustic Logging Applications 554
19.5.1 Formation Fluid Pressure 555
19.5.2 Mechanical Properties and Fractures 557
19.5.3 Permeability 559
19.5.4 Cement Bond Log 561
19.6 Ultrasonic Devices 562
19.6.1 Pulse-Echo Imaging 563
19.6.2 Cement Evaluation 565
References 566
Problems 568
20 High Angle and Horizontal Wells 573
20.1 Introduction 573
20.2 Why are HA/HZ Wells Different? 574
20.3 Measurement Response 576
20.3.1 Resistivity 577
20.3.2 Density 580
20.3.3 Neutron 582
20.3.4 Other Measurements 584
20.4 Geosteering 585
20.4.1 Deep Reading Devices for Geosteering 589
References 593
Problems 594
21 Clay Quantification 597
21.1 Introduction 597
21.2 What is Clay/Shale? 598
21.2.1 Physical Properties of Clays 599
21.2.2 Total Porosity and Effective Porosity 601
21.2.3 Shale Distribution 604
21.2.4 Influence on Logging Measurements 606
21.3 Shale Determination from Single Measurements 609
21.3.1 Interpretation of Pe in Shaly Sands 610
21.3.2 Neutron Response to Shale 613
xvi CONTENTS
21.3.3 Response of to Clay Minerals 616
21.4 Neutron–Density Plots 617
21.5 Elemental Analysis 621
21.6 Clay Typing 624
References 624
Problems 626
22 Lithology and Porosity Estimation 629
22.1 Introduction 629
22.2 Graphical Approach for Binary Mixtures 630
22.3 Combining Three Porosity Logs 636
22.3.1 Lithology Logging: Incorporating Pe 640
22.3.2 Other Methods 643
22.4 Numerical Approaches to Lithology Determination 644
22.4.1 Quantitative Evaluation 647
22.5 General Evaluation Methods 648
References 650
Problems 651
23 Saturation and Permeability Estimation 653
23.1 Introduction 653
23.2 Clean Formations 654
23.3 Shaly Formations 658
23.3.1 Early Models 661
23.3.2 Double Layer Models 662
23.3.3 Saturation Equations 665
23.3.4 Laminated Sands 668
23.4 Carbonates and Heterogeneous Rocks 671
23.5 Permeability from Logs 674
23.5.1 Resistivity and Porosity 675
23.5.2 Petrophysical Models 676
References 681
Problems 684
Index 687
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