Seismic While Drilling (eBook)

Cover 1
Contents 7
Preface 17
Preface by Authors 20
Acknowledgments 22
About the Authors 23
Glossary of Main Symbols 25
Conversion Factors for the Main Physical Quantities 26
Introduction and Overview 27
Geophysics for Exploration and Drilling 27
Geophysical Monitoring of Drilling 28
Conventional Borehole Seismic Methods 29
Vertical Seismic Profile 29
Typical Acquisition Geometries of Conventional VSP 31
Conventional Processing of VSP Data 32
Other uses of Conventional VSP 36
Synthetic Seismogram 38
Integrated Interpretation of Well Seismic Data 40
Motivation for Seismic While Drilling 40
Challenges and Potentials of the New Technology 42
Nomenclature Used for Seismic While Drilling 42
History of the Use of the Drill-bit Signal 43
Overview of the Different Approaches to SWD 46
Seismic-while-drilling Method 47
Main Products Obtainable While Drilling 50
Measurement While Drilling and SWD Perspectives 50
Principles of Drilling 53
Introduction 53
Drilling a Well 53
Main Well Components 54
Drilling Site 54
Derrick 55
Rig Power System 58
Drawwork 58
Rope Lines 58
Mobile-hoisting Block 59
Rotary Systems 59
Top Drive 60
Rotary-table or Kelly System 62
Downhole Rotary Systems 62
Downhole Motors 63
Turbines 63
Use of Positive-displacement Motors and Turbines 65
Drilling Floor or Rotary Kelly-bush Level 65
Wellhead and Blow Out Preventers 66
Drill String 66
Drill Pipes 66
Bottom Hole Assembly (BHA) 68
Drill-string Loads 69
Drill-string Dimension and Safe Rotary Speeds 69
The Bit 71
Roller-cone Bit 72
Natural Diamond Bits 74
Polycrystalline Diamond Compact (PDC) Bit 74
Bicenter PDC Bit 76
Casing 77
Pumps 77
Drilling Mud 79
Mud Circulating Line 81
Logistics and Laboratories 81
Drilling Parameters and Mudlogging 83
Measurement While Drilling and Mud-pulse Telemetry 84
Mud Pulse 84
Electromagnetic 84
Logging While Drilling 85
Wellsite Communication Systems 86
Drilling Offshore 87
Bottom Supported Systems 87
Floating Systems 88
Directional and Deviated Wells 88
Directional Drilling 90
Monitoring Directional Drilling 92
Axial Loads in Directional Wells 93
Drill-string Rotation and Axial Forces 93
Horizontal and Extended-reach Drilling 93
Multi-lateral Wells 95
Steering of Drilling 95
Slim Holes and Coil Tubing 95
Designing a Well 96
Evaluation of the Borehole Pressure 98
Selection of the Casing Depths (Seats) 99
Design of the Mud Plan and Subsurface Well Control 99
Design of the Bottom-hole Assembly 101
Dogleg Severity, Drill-pipe Fatigue and Key-seat Problems 101
Sticking of Pipes 102
Other Problems Related to Doglegs 102
BHA Rigidity and Drill-string Stabilization 102
Packed-hole Assembly 104
Pendulum Assembly 105
Reducing Weight on Bit 106
Stiffness of the Drill Collars 106
Design of the Cross Sections and Bending Stresses 108
Bottom-hole-assembly Buckling 108
Bit Planning 111
Formation Hardness/Abrasiveness 111
Directional Control and Bit Type 112
Bit Selection and Drilling Method 113
Coring Bits 113
Bit Size 114
Bit and Rotary Speed 114
Evaluation of Bit Wear 114
Classification of Drill-bit Types 115
Roller-bit Classification According to IADC 115
Major-group (or "Series") Classification 115
Sub-group (or "Type") Classification 115
Specialty Feature 115
Bit Cones 115
Diamond Bit Classification 117
PDC Bits 117
Fixed Cutter Classification According to IADC 117
General Theory: Drill-bit Seismic Waves 119
Introduction 119
Reciprocity Principle 120
Normal While-drilling VSP 121
Seismic Measurement While Drilling SMWD 121
Seismic MWD System 121
SMWD Operational Conditions and Features 122
Drill-bit Seismic Source 123
Drill-bit Signal Characterization 123
Total Drilling Power 124
Energy Losses for Drill-string Torque Friction 125
Effects of Drag Friction 125
Downhole Motor Drilling 126
Energy Analysis in Terms of Drilling Parameters 126
Specific Energy „ Required to Drill a Unit Volume of Rock 126
"Perfect-cleaning" Theory of Drilling 127
Dimensionless Drilling Parameters 128
Rotary-drilling Model (Dimensionless Parameters) 128
Energy Balance in Rock Fracture 129
New-surface Energy 130
"Elastic-strain" (Heat) Energy 130
Stress Waves Produced in Loading/Unloading 131
Radiation of Energy from the Bit (Far-field Effects) 133
Radiation from a Surface Harmonic Force 135
Radiation from a Downhole Harmonic Force 136
Integrated Downhole-radiation Impedance 139
Total P+SV Power Radiated in the Formation 140
Radiation from a Non-harmonic Force 141
Near-field Effects 141
Phase of the Harmonic Wave Components 143
Near-field Axial Displacement 144
Energy Flux and Near-field Effects 146
Complex Impedance 147
Waves from a Pressure Source at the Origin 148
Relation between Rotary-drilling Power and Radiated Power 149
Balance of the Borehole and Radiated Power 150
Special Considerations 151
Partition of Radiated and Drill-string Powers 152
Measuring the Power of Axial Drill-string Waves 153
Drill Bit Versus Conventional Seismic Sources 154
Roller-cone Bit as a Periodic Vibration Source 155
Vibrations Induced by Teeth Indention 156
Vibrations Induced by Lobed Patterns 158
Pore Pressure and Roller-cone Bit Forces 161
Effects of Teeth Wear on Roller-cone Vibrations 165
Roller-cone Bit as a Wideband Seismic Source 166
Unevenness of the Formation, Random Breakage Process 166
Bandwidth Amplification by Vibration-mode Coupling 168
Torsional Modulation of Lobe-axial Vibrations 169
Roller-cone Bit as a High-frequency Source 170
PDC Bit as a Vibration Source 170
Analysis of PDC Single-cutter Forces 170
Direction of Single-cutter Force 172
Influence of Wear on PDC Performance Parameters 172
Influence of Downhole Pressure on Cutter Forces 173
Dynamic Variation of PDC-cutter Forces 173
Tilted Bed Boundaries 173
Drilling Nodules 174
Whirling Bits 174
Dynamic Models of the PDC Axial Vibrations 175
Summary of Large Bit-vibration Modes 176
Bit Vibrations Induced by Mud Pressure Modulation 176
Numerical Examples of Drill-bit Vibrations 178
Radiation Properties of Conventional Sources 181
Vibroseis Source 181
Single Vertical Vibrator 181
Array of Vertical Vibrators 183
Radiation from Marine Sources 183
Air and Water Guns 184
Radiation from Drill-bit and Conventional Sources 184
General Theory: Drill-string Waves and Noise Fields 189
Introduction: Drill-string Vibration Analysis 189
Drill-string Waves 190
Axial Drill-string Waves 191
Torsional Drill-string Waves 193
Transversal and Flexural Drill-string Waves 194
Vibrating-rope Approximation 195
Bending Vibrations 195
Coupled Extensional and Flexural Drill-string Waves 196
Attenuation of Extensional Waves 196
Attenuation of Vibrations by Shock Absorbers 197
Waves in Periodic and Non-periodic Drill Strings 200
Wave Propagation in Periodic Strings 200
Wave Propagation in Non-periodic Strings 203
Group Velocity in Non-periodic String 203
Average Drill-string Properties 204
Average Dynamic Properties 204
Average Static Properties 205
Group Velocity at Low Frequency 206
Example of Group Velocity 206
Drill-bit Mud Waves 207
Guided Waves in SWD Data 208
Acoustic Properties of Drilling Mud 208
Velocities of the Acoustic Mud Waves 209
Sensitivity Analysis for Acoustic Mud Velocity 209
Velocities of the Guided Waves 211
Sensitivity Analysis for Velocity of Mud Guided Waves 212
Coupled Pipe-mud-formation Guided Waves 213
Conical Head Waves in the Formation (Borehole Radiation) 215
Mach Shear Waves 215
Drill-string Head Waves 215
Summary of Drill String Waves 216
Surface/Rigsite Noise Wavefields 217
Drill-string Noise and Borehole Interactions 219
Surface Rig Suspension Vibrations 219
Lateral Swivel Vibrations 220
Lateral Bending Vibrations 220
Pipe Buckling and Static Friction Effects 222
Deviation Contacts 222
Drill-string Transmission Line 224
Reflection Coefficients in the Drill String 225
Bit/Rock Reflection Coefficient 227
Bit/Rock Reflection Coefficient (Plane-wave Approximation) 228
The Constitutive Equations (Bit/Rock Contact) 228
Real Bit/Rock Reflection Coefficient (Plane Waves) 229
Bit/Rock Coefficient and Formation Impedance 230
Complex Bit/Rock Reflection Coefficient (Near-field Approximation) 230
Drill-string Waves and Near-field Effects 230
Complex Bit/Rock Coefficient 232
Dual Fields in the Drill String 234
Dual (Displacement and Strain) Reflection Coefficients 235
Reflection Coefficients of Displacement Waves 236
Reflection Coefficients of Strain Waves 236
Dual Fields in the Drill-string Transmission Line 238
Acquisition of SWD Data 239
Introduction 239
Signal Recognition and Acquisition Layout 240
Pilot Sensors and Transducers 242
Accelerometers 243
Main Characteristics of Accelerometers 245
Piezoelectric Accelerometers 246
Damped Geophones as Accelerometers 247
Strain Gages 247
Temperature and Gage Selection 248
Strain Gage Response 248
Strain Gage Installation 248
Force and Pressure Transducers 248
Torque Transducer 250
Surface Pilot Sensors (Rig Pilots) 250
Pilot Sensors on the Top of the Drill String 251
Swivel System 251
Top-drive System 251
Surface Pilot Sensors in the Rotating Drill String 253
Downhole Pilot Sensors 254
Use of Dual Sensors in Drill Strings 257
Other Pilot Sensors at the Rig 259
Derrick Pilot Sensors 259
Mud-pressure Pilot 259
Torque Pilot 261
Yard Noise 261
Connections of Rig Pilots to the Recording System 261
SWD Data-acquisition System 262
Other SWD Commercial Systems 264
TOMEX Seismic-while-drilling Field System (Baker Atlas) 264
Drill-bit Seismic - DBSeis System (Schlumberger) 265
SWD-data Acquisition and Drilling Control 266
Automatic SWD Acquisition by Using Drilling Parameters 268
Selection of Data by Drilling Parameters 268
Drilling Depth and Seismic Depth 271
Vertical Well 271
Deviated Well 273
Spatial Sampling of SWD Signals 273
Common-receiver Gathers 273
Common-source Gathers 274
SWD-source Pattern with Bit Deepening 274
Data without Correction to Zero Time 276
Onshore Acquisition 276
Seismic Line 276
Receiver Arrays in SWD 281
Random Noise 282
Coherent Noise 283
Number of Receivers and Noise Attenuation 285
Analysis of Optimum Arrays 285
Coherent and Random Noise in SWD Geophone Arrays 288
Experiments with Receiver Arrays in Onshore SWD 292
Acquisition of Shear and Converted Waves 294
Survey Preparation Procedures 296
Refraction Statics for Seismic While Drilling 296
Field Statics in SWD Arrays 298
Survey Operations 301
Summary of Quality-control Procedures 302
Instrumental Tests 302
Initial QC Tests 303
QC Tests with the Variation of the Bit Depth 304
Periodical QC Tests 304
Auxiliary QC Tests 307
Onshore 3D-SWD Acquisition 307
3D Acquisition System 308
Offshore Acquisition 308
Offshore SWD Wavefields 308
Offshore SWD Application (Using Fixed Receivers) 310
Offshore Operations 314
Extension of Offshore SWD (Using Towed Streamers) 314
Preprocessing of SWD Data 317
Introduction 317
Preprocessing 317
SWD Data in the Crosscorrelated Domain 318
Basic Crosscorrelation Properties 318
Energy in Crosscorrelation 320
Delays in Crosscorrelation 320
Crosscorrelation and Filtering 321
Crosscorrelation of Signal and Noise 325
Stack of While-drilling Data 327
Vertical Stack and Correlation Error 329
Deconvolution of the Drill-bit Source Function 329
Pilot Deconvolution 332
Crosscorrelation, Stack and Pilot Deconvolution 333
Discussion about Pilot Deconvolution 334
Beam-steering Deconvolution 335
Focused Pilot 335
Optimum Beam Forming of the Drill-bit Signature 338
Autocorrelation Bias 339
Deconvolution in Rotation-angle Domain 340
Analysis of Synthetic and Real Data in Rotation-angle Domain 341
Modeling of Drill-string Response 341
Propagation Matrix for Drill-bit Signal 341
Propagation Matrix for Rig Noise 343
Reflection Coefficients in Two-way Travel Time (TWT) 344
Fitting with Real Data 345
Drill-string Waves in the Correlated and Deconvolved Data 347
Interpretation of Drill-string Multiples 350
Drill-string Multiples in Pilot Data 350
Drill-string Multiples in Geophone Data 352
Rig Ghost 353
Processing of Dual Drill-string Wavefields 355
Synthetic Dual Wavefields 355
Real Examples with Axial Dual Waves 356
Deconvolution of Pilot Dual Fields 359
Pilot-delay Correction 360
Use of Pilot Signals with Different Delays 361
Signal Rephasing 362
Rephasing after Pilot Deconvolution 362
Rephasing before Pilot Deconvolution 365
Shaping to Minimum Phase 365
Example of Preprocessing Parameters 366
Processing of Signal and Noise RVSP Fields 371
Introduction 371
Entropy and Repeatability of the Drill-bit Source 371
Common-level Stack of Correlations with Noise 373
Vertical-stack Model 374
Optimum Weights (General Case) 376
Special Cases of Level Stack 377
Selective Stack by Drilling Parameters 378
Noise Cancellation by Orthogonal Pilot Traces 380
Noise Separation by Independent Pilot Traces 383
Gaussian and Non-Gaussian Processes 384
Uncorrelated Drill-bit Signal and RVSP's 385
Incorrelation and Independence 385
General Approach 387
Statistical Independence of Drill-bit Data 388
Independence of Real Data 388
Analysis of Torsional Pilot Waves 391
SWD with Downhole-motor Drilling 392
Downhole Pilot Signals 394
Mud Guided-waves Pilot Signals 394
Interpretation of Mud-guided Waves 398
Sensitivity Analysis for Mud Velocity 401
RVSP Processing of SWD-VSP Seismograms 401
Direct-arrival, First-Break Picking (FB) 401
Picking Arrivals of Common-receiver Data 401
Picking of Common-source Data 402
Gain Recovery 402
Wavefield Separation 402
Separation of Downgoing and Upgoing Waves for Reflection Processing 402
Separation of Correlated Signal and Coherent Noise after Preprocessing 404
VSP Deconvolution 404
Downgoing and Upgoing Deconvolution Operator 404
Log-spectrum (Cepstral) Analysis of Drill-bit Correlations 405
Velocity Analysis 406
Analysis of Impulsive Drill-bit Signal 406
The "Impulsive" VSP Drill-bit Data 407
Kurtosis of Drill-bit Seismograms 410
Correction for Geophone Group-array Filters 412
Other SWD Methods Based on Correlation 412
Crosscorrelogram Migration 412
Formation Analysis by Pilot Seismograms 413
Reflections in Pilot and Geophone Seismograms 415
Pilot VSP Interpretation 415
Applications 419
Introduction 419
SWD Products 420
Checkshot 420
Reflectivity Characterization 421
Prediction Ahead-of-the-bit 423
Multioffset VSP 424
Lateral Images and Resolution 424
Improved Velocity Analysis 424
Improved Reflections for Prediction 424
Geophysical Monitoring of the Well 426
Drilling and Real-time Migration 426
Deviated-well Monitoring 428
Geological and Lithological Aspects 430
SWD with Different Lithological Conditions 430
Estimating Acoustic Impedance from SWD Data 434
Comparison of SWD and Wireline VSP Results 434
Prediction by SWD in Favorable Conditions 435
SWD in Geologically-complex and Poor-seismic-response Area 437
SWD Applications in the Val d'Agri 442
Comparison of SWD and Seismic Velocities 443
Prediction of Acoustic Interfaces Ahead of the Bit 443
Structural Reconstruction Near the Well by Multioffset 443
Isolation of Zones with Different Pressure Gradients 448
Prediction by SWD-RVSP Tomography 448
Crosshole SWD Seismic Survey 450
Data Reorientation and Wavefield Analysis 453
Polarization Analysis and Vertical Reorientation 455
Radiation-pattern Analysis 458
Anisotropy 461
Tomographic Reconstruction of the SV Velocity Field 462
3D-RVSP Application 462
Geological Setting of the 3D-SWD Case History 462
Modeling of 3D-SWD Survey 462
3D-RVSP Survey Organization and Layout 464
Azimuthal Analysis of Rig-radiated Noise 467
While-drilling Analysis of 3D Data 467
Prediction of Reflecting Interfaces by Near-offset RVSP 470
While-drilling Multioffset RVSP 470
Comparison of SWD Results, Conventional VSP and Well-log Data 470
Analysis of Shear-wave Data 473
Anisotropy Analysis 473
3D-RVSP Migration of SWD Data 474
Model Computation for 3D Static Correction 474
3D-SWD Seismic Tomography 474
3D-RVSP Migration 474
3D-SWD Migrated Data Tied to Surface Seismics 476
Interpretation of 3D-RVSP Cube 476
While-drilling Application of 3D-RVSP Imaging 479
Geological Setting and Exploration Problems 479
Work Flow and 3D-while-drilling Seismic Imaging 479
While-drilling 3D Results 479
New Trends for SWD 480
SWD in Deep Water 480
The Common-position Drill-bit Method 482
The Errors Introduced by Streamer Towing 484
Acquisition Technology and Data Flow of Offshore CP-SWD 487
CP-SWD Acquisition Geometry: Offshore 2D Versus 3D 487
SWD in Highly-deviated Wells 488
Geopressure Prediction and Assessment 488
The Road Ahead: SWD by Downhole Technology 491
Drilling Diagnostics and Geosteering 492
Geosteering 493
Bibliography 495
Name Index 519
Subject Index 527