Cover image for An introduction to geophysical exploration
Title:
An introduction to geophysical exploration
Personal Author:
Edition:
3rd ed.
Publication Information:
Oxford : Blackwell Science, 2002
ISBN:
9780632049295

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30000010045982 TN269 K42 2002 Open Access Book Book
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Summary

Summary

This new edition of the well-established Kearey and Brooks text is fully updated to reflect the important developments in geophysical methods since the production of the previous edition. The broad scope of previous editions is maintained, with even greater clarity of explanations from the revised text and extensively revised figures. Each of the major geophysical methods is treated systematically developing the theory behind the method and detailing the instrumentation, field data acquisition techniques, data processing and interpretation methods. The practical application of each method to such diverse exploration applications as petroleum, groundwater, engineering, environmental and forensic is shown by case histories.

The mathematics required in order to understand the text is purposely kept to a minimum, so the book is suitable for courses taken in geophysics by all undergraduate students. It will also be of use to postgraduate students who might wish to include geophysics in their studies and to all professional geologists who wish to discover the breadth of the subject in connection with their own work.


Author Notes

Philip Kearey gained a B.Sc. in Geology and a Ph.D. in Geophysics at the University of Durham. After two years working for the Canadian government he took up a post as Lecturer in Applied Geophysics at the University of Bristol in 1976. He was promoted to Senior Lecturer in 1995. He was elected as Chartered Geologist of the Geological Society in 1991.

Mike Brooks was a Professor of Geology and Head of the Department of Geology at Cardiff University from 1978 to 1993 and is now a Professor Emeritus of the University. From 1993 to 2001 he was the Education and Training Officer of the Geological Society of London.

Ian Hill is Senior Lecturer in Geophysics at the University of Leicester where he teaches Geophysics and Plate Tectonics. He was the first chairman of the Environmental and Industrial Geophysics Group (EIGG) of the Geological Society of London. He is a Chartered Geologist.


Table of Contents

Prefacep. ix
1 The principles and limitations of geophysical exploration methodsp. 1
1.1 Introductionp. 1
1.2 The survey methodsp. 1
1.3 The problem of ambiguity in geophysical interpretationp. 6
1.4 The structure of the bookp. 7
2 Geophysical data processingp. 8
2.1 Introductionp. 8
2.2 Digitization of geophysical datap. 8
2.3 Spectral analysisp. 10
2.4 Waveform processingp. 13
2.4.1 Convolutionp. 13
2.4.2 Deconvolutionp. 16
2.4.3 Correlationp. 16
2.5 Digital filteringp. 17
2.5.1 Frequency filtersp. 18
2.5.2 Inverse (deconvolution) filtersp. 19
2.6 Imaging and modellingp. 19
Problemsp. 20
Further readingp. 20
3 Elements of seismic surveyingp. 21
3.1 Introductionp. 21
3.2 Stress and strainp. 21
3.3 Seismic wavesp. 22
3.3.1 Body wavesp. 23
3.3.2 Surface wavesp. 24
3.3.3 Waves and raysp. 25
3.4 Seismic wave velocities of rocksp. 26
3.5 Attenuation of seismic energy along ray pathsp. 27
3.6 Ray paths in layered mediap. 28
3.6.1 Reflection and transmission of normally incident seismic raysp. 28
3.6.2 Reflection and refraction of obliquely incident raysp. 30
3.6.3 Critical refractionp. 31
3.6.4 Diffractionp. 31
3.7 Reflection and refraction surveyingp. 32
3.8 Seismic data acquisition systemsp. 33
3.8.1 Seismic sources and the seismic/acoustic spectrump. 34
3.8.2 Seismic transducersp. 39
3.8.3 Seismic recording systemsp. 41
Problemsp. 42
Further readingp. 42
4 Seismic reflection surveyingp. 43
4.1 Introductionp. 43
4.2 Geometry of reflected ray pathsp. 43
4.2.1 Single horizontal reflectorp. 43
4.2.2 Sequence of horizontal reflectorsp. 45
4.2.3 Dipping reflectorp. 46
4.2.4 Ray paths of multiple reflectionsp. 47
4.3 The reflection seismogramp. 48
4.3.1 The seismic tracep. 48
4.3.2 The shot gatherp. 49
4.3.3 The CMP gatherp. 50
4.4 Multichannel reflection survey designp. 51
4.4.1 Vertical and horizontal resolutionp. 52
4.4.2 Design of detector arraysp. 53
4.4.3 Common mid-point (CMP) surveyingp. 54
4.4.4 Display of seismic reflection datap. 57
4.5 Time corrections applied to seismic tracesp. 57
4.6 Static correctionp. 57
4.7 Velocity analysisp. 59
4.8 Filtering of seismic datap. 61
4.8.1 Frequency filteringp. 62
4.8.2 Inverse filtering (deconvolution)p. 62
4.8.3 Velocity filteringp. 65
4.9 Migration of reflection datap. 67
4.10 3D seismic reflection surveysp. 72
4.11 Three component (3C) seismic reflection surveysp. 76
4.12 4D seismic reflection surveysp. 77
4.13 Vertical seismic profilingp. 79
4.14 Interpretation of seismic reflection datap. 80
4.14.1 Structural analysisp. 81
4.14.2 Stratigraphical analysis (seismic stratigraphy)p. 82
4.14.3 Seismic modellingp. 84
4.14.4 Seismic attribute analysisp. 85
4.15 Single-channel marine reflection profilingp. 86
4.15.1 Shallow marine seismic sourcesp. 89
4.15.2 Sidescan sonar systemsp. 90
4.16 Applications of seismic reflection surveyingp. 92
Problemsp. 97
Further readingp. 98
5 Seismic refraction surveyingp. 99
5.1 Introductionp. 99
5.2 Geometry of refracted ray paths: planar interfacesp. 99
5.2.1 Two-layer case with horizontal interfacep. 100
5.2.2 Three-layer case with horizontal interfacep. 101
5.2.3 Multilayer case with horizontal interfacesp. 102
5.2.4 Dipping-layer case with planar interfacesp. 102
5.2.5 Faulted planar interfacesp. 104
5.3 Profile geometries for studying planar layer problemsp. 105
5.4 Geometry of refracted ray paths: irregular (non-planar) interfacesp. 106
5.4.1 Delay timep. 106
5.4.2 The plus-minus interpretation methodp. 108
5.4.3 The generalized reciprocal methodp. 109
5.5 Construction of wavefronts and ray-tracingp. 110
5.6 The hidden and blind layer problemsp. 110
5.7 Refraction in layers of continuous velocity changep. 112
5.8 Methodology of refraction profilingp. 112
5.8.1 Field survey arrangementsp. 112
5.8.2 Recording schemep. 113
5.8.3 Weathering and elevation correctionsp. 114
5.8.4 Display of refraction seismogramsp. 115
5.9 Other methods of refraction surveyingp. 115
5.10 Seismic tomographyp. 117
5.11 Applications of seismic refraction surveyingp. 119
5.11.1 Engineering and environmental surveysp. 119
5.11.2 Hydrological surveysp. 120
5.11.3 Crustal seismologyp. 120
5.11.4 Two-ship seismic surveying: combined refraction and reflection surveyingp. 122
Problemsp. 123
Further readingp. 124
6 Gravity surveyingp. 125
6.1 Introductionp. 125
6.2 Basic theoryp. 125
6.3 Units of gravityp. 126
6.4 Measurement of gravityp. 126
6.5 Gravity anomaliesp. 129
6.6 Gravity anomalies of simple-shaped bodiesp. 130
6.7 Gravity surveyingp. 132
6.8 Gravity reductionp. 133
6.8.1 Drift correctionp. 133
6.8.2 Latitude correctionp. 133
6.8.3 Elevation correctionsp. 134
6.8.4 Tidal correctionp. 136
6.8.5 Eotvos correctionp. 136
6.8.6 Free-air and Bouguer anomaliesp. 136
6.9 Rock densitiesp. 137
6.10 Interpretation of gravity anomaliesp. 139
6.10.1 The inverse problemp. 139
6.10.2 Regional fields and residual anomaliesp. 139
6.10.3 Direct interpretationp. 140
6.10.4 Indirect interpretationp. 142
6.11 Elementary potential theory and potential field manipulationp. 144
6.12 Applications of gravity surveyingp. 147
Problemsp. 150
Further readingp. 153
7 Magnetic surveyingp. 155
7.1 Introductionp. 155
7.2 Basic conceptsp. 155
7.3 Rock magnetismp. 158
7.4 The geomagnetic fieldp. 159
7.5 Magnetic anomaliesp. 160
7.6 Magnetic surveying instrumentsp. 162
7.6.1 Introductionp. 162
7.6.2 Fluxgate magnetometerp. 162
7.6.3 Proton magnetometerp. 163
7.6.4 Optically pumped magnetometerp. 164
7.6.5 Magnetic gradiometersp. 164
7.7 Ground magnetic surveysp. 164
7.8 Aeromagnetic and marine surveysp. 164
7.9 Reduction of magnetic observationsp. 165
7.9.1 Diurnal variation correctionp. 165
7.9.2 Geomagnetic correctionp. 166
7.9.3 Elevation and terrain correctionsp. 166
7.10 Interpretation of magnetic anomaliesp. 166
7.10.1 Introductionp. 166
7.10.2 Direct interpretationp. 168
7.10.3 Indirect interpretationp. 170
7.11 Potential field transformationsp. 172
7.12 Applications of magnetic surveyingp. 173
Problemsp. 180
Further readingp. 181
8 Electrical surveyingp. 183
8.1 Introductionp. 183
8.2 Resistivity methodp. 183
8.2.1 Introductionp. 183
8.2.2 Resistivities of rocks and mineralsp. 183
8.2.3 Current flow in the groundp. 184
8.2.4 Electrode spreadsp. 186
8.2.5 Resistivity surveying equipmentp. 186
8.2.6 Interpretation of resistivity datap. 187
8.2.7 Vertical electrical sounding interpretationp. 188
8.2.8 Constant separation traversing interpretationp. 193
8.2.9 Limitations of the resistivity methodp. 196
8.2.10 Applications of resistivity surveyingp. 196
8.3 Induced polarization (IP) methodp. 199
8.3.1 Principlesp. 199
8.3.2 Mechanisms of induced polarizationp. 199
8.3.3 Induced polarization measurementsp. 200
8.3.4 Field operationsp. 201
8.3.5 Interpretation of induced polarization datap. 201
8.3.6 Applications of induced polarization surveyingp. 202
8.4 Self-potential (SP) methodp. 203
8.4.1 Introductionp. 203
8.4.2 Mechanism of self-potentialp. 203
8.4.3 Self-potential equipment and survey procedurep. 203
8.4.4 Interpretation of self-potential anomaliesp. 204
Problemsp. 205
Further readingp. 207
9 Electromagnetic surveyingp. 208
9.1 Introductionp. 208
9.2 Depth of penetration of electromagnetic fieldsp. 208
9.3 Detection of electromagnetic fieldsp. 209
9.4 Tilt-angle methodsp. 209
9.4.1 Tilt-angle methods employing local transmittersp. 210
9.4.2 The VLF methodp. 210
9.4.3 The AFMAG methodp. 212
9.5 Phase measuring systemsp. 212
9.6 Time-domain electromagnetic surveyingp. 214
9.7 Non-contacting conductivity measurementp. 216
9.8 Airborne electromagnetic surveyingp. 218
9.8.1 Fixed separation systemsp. 218
9.8.2 Quadrature systemsp. 220
9.9 Interpretation of electromagnetic datap. 221
9.10 Limitations of the electromagnetic methodp. 221
9.11 Telluric and magnetotelluric field methodsp. 221
9.11.1 Introductionp. 221
9.11.2 Surveying with telluric currentsp. 222
9.11.3 Magnetotelluric surveyingp. 224
9.12 Ground-penetrating radarp. 225
9.13 Applications of electromagnetic surveyingp. 227
Problemsp. 228
Further readingp. 230
10 Radiometric surveyingp. 231
10.1 Introductionp. 231
10.2 Radioactive decayp. 231
10.3 Radioactive mineralsp. 232
10.4 Instruments for measuring radioactivityp. 233
10.4.1 Geiger counterp. 233
10.4.2 Scintillation counterp. 233
10.4.3 Gamma-ray spectrometerp. 233
10.4.4 Radon emanometerp. 234
10.5 Field surveysp. 235
10.6 Example of radiometric surveyingp. 235
Further readingp. 235
11 Geophysical borehole loggingp. 236
11.1 Introduction to drillingp. 236
11.2 Principles of well loggingp. 236
11.3 Formation evaluationp. 237
11.4 Resistivity loggingp. 237
11.4.1 Normal logp. 238
11.4.2 Lateral logp. 239
11.4.3 Laterologp. 240
11.4.4 Micrologp. 241
11.4.5 Porosity estimationp. 241
11.4.6 Water and hydrocarbon saturation estimationp. 241
11.4.7 Permeability estimationp. 242
11.4.8 Resistivity dipmeter logp. 242
11.5 Induction loggingp. 243
11.6 Self-potential loggingp. 243
11.7 Radiometric loggingp. 244
11.7.1 Natural gamma radiation logp. 244
11.7.2 Gamma-ray density logp. 244
11.7.3 Neutron-gamma-ray logp. 245
11.8 Sonic loggingp. 246
11.9 Temperature loggingp. 247
11.10 Magnetic loggingp. 247
11.10.1 Magnetic logp. 247
11.10.2 Nuclear magnetic resonance logp. 247
11.11 Gravity loggingp. 247
Problemsp. 248
Further readingp. 249
Appendix SI, c.g.s. and Imperial (customary USA) units and conversion factorsp. 250
Referencesp. 251
Indexp. 257