An Introduction to Geophysical Exploration

by Kearey, Philip; Brooks, Michael; Hill, Ian

• ISBN13: 9780632049295
• ISBN10: 0632049294
• Edition: 3rd
• Format: Paperback
• Copyright: 2002-04-26
• Publisher: Wiley-Blackwell

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 Biography

Philip Kearey gained a B.Sc. in Geology and a Ph.D. in Geophysics at the University of Dunham. After two years 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 Geoligist.

Table of Contents

Preface	ix
The principles and limitations of geophysical exploration methods	1	(7)
Introduction	1	(1)
The survey methods	1	(5)
The problem of ambiguity in geophysical interpretation	6	(1)
The structure of the book	7	(1)
Geophysical data processing	8	(13)
Introduction	8	(1)
Digitization of geophysical data	8	(2)
Spectral analysis	10	(3)
Waveform processing	13	(4)
Convolution	13	(3)
Deconvolution	16	(1)
Correlation	16	(1)
Digital filtering	17	(2)
Frequency filters	18	(1)
Inverse (deconvolution) filters	19	(1)
Imaging and modelling	19	(2)
Problems	20	(1)
Further reading	20	(1)
Elements of seismic surveying	21	(22)
Introduction	21	(1)
Stress and strain	21	(1)
Seismic waves	22	(4)
Body waves	23	(1)
Surface waves	24	(1)
Waves and rays	25	(1)
Seismic wave velocities of rocks	26	(1)
Attenuation of seismic energy along ray paths	27	(1)
Ray paths in layered media	28	(4)
Reflection and transmission of normally incident seismic rays	28	(2)
Reflection and refraction of obliquely incident rays	30	(1)
Critical refraction	31	(1)
Diffraction	31	(1)
Reflection and refraction surveying	32	(1)
Seismic data acquisition systems	33	(10)
Seismic sources and the seismic/acoustic spectrum	34	(5)
Seismic transducers	39	(2)
Seismic recording systems	41	(1)
Problems	42	(1)
Further reading	42	(1)
Seismic reflection surveying	43	(56)
Introduction	43	(1)
Geometry of reflected ray paths	43	(5)
Single horizontal reflector	43	(2)
Sequence of horizontal reflectors	45	(1)
Dipping reflector	46	(1)
Ray paths of multiple reflections	47	(1)
The reflection seismogram	48	(3)
The seismic trace	48	(1)
The shot gather	49	(1)
The CMP gather	50	(1)
Multichannel reflection survey design	51	(6)
Vertical and horizontal resolution	52	(1)
Design of detector arrays	53	(1)
Common mid-point (CMP) surveying	54	(3)
Display of seismic reflection data	57	(1)
Time corrections applied to seismic traces	57	(1)
Static correction	57	(2)
Velocity analysis	59	(2)
Filtering of seismic data	61	(6)
Frequency filtering	62	(1)
Inverse filtering (deconvolution)	62	(3)
Velocity filtering	65	(2)
Migration of reflection data	67	(5)
3D seismic reflection surveys	72	(4)
Three component (3C) seismic reflection surveys	76	(1)
4D seismic reflection surveys	77	(2)
Vertical seismic profiling	79	(1)
Interpretation of seismic reflection data	80	(6)
I Structural analysis	81	(1)
Stratigraphical analysis (seismic stratigraphy)	82	(2)
Seismic modelling	84	(1)
Seismic attribute analysis	85	(1)
Single-channel marine reflection profiling	86	(6)
Shallow marine seismic sources	89	(1)
Sidescan sonar systems	90	(2)
Applications of seismic reflection surveying	92	(7)
Problems	97	(1)
Further reading	98	(1)
Seismic refraction surveying	99	(26)
Introduction	99	(1)
Geometry of refracted ray paths: planar interfaces	99	(6)
Two-layer case with horizontal interface	100	(1)
Three-layer case with horizontal interface	101	(1)
Multilayer case with horizontal interfaces	102	(1)
Dipping-layer case with planar interfaces	102	(2)
Faulted planar interfaces	104	(1)
Profile geometries for studying planar layer problems	105	(1)
Geometry of refracted ray paths: irregular (non-planar) interfaces	106	(4)
Delay time	106	(2)
The plus-minus interpretation method	108	(1)
The generalized reciprocal method	109	(1)
Construction of wave fronts and ray-tracing	110	(1)
The hidden and blind layer problems	110	(2)
Refraction in layers of continuous velocity change	112	(1)
Methodology of refraction profiling	112	(3)
Field survey arrangements	112	(1)
Recording scheme	113	(1)
Weathering and elevation corrections	114	(1)
Display of refraction seismograms	115	(1)
Other methods of refraction surveying	115	(2)
Seismic tomography	117	(2)
Applications of seismic refraction surveying	119	(6)
Engineering and environmental surveys	119	(1)
Hydrological surveys	120	(1)
Crustal seismology	120	(2)
Two-ship seismic surveying: combined refraction and reflection surveying	122	(1)
Problems	123	(1)
Further reading	124	(1)
Gravity surveying	125	(30)
Introduction	125	(1)
Basic theory	125	(1)
Units of gravity	126	(1)
Measurement of gravity	126	(3)
Gravity anomalies	129	(1)
Gravity anomalies of simple-shaped bodies	130	(2)
Gravity surveying	132	(1)
Gravity reduction	133	(4)
Drift correction	133	(1)
Latitude correction	133	(1)
Elevation corrections	134	(2)
Tidal correction	136	(1)
Eotvos correction	136	(1)
Free-air and Bouguer anomalies	136	(1)
Rock densities	137	(2)
Interpretation of gravity anomalies	139	(5)
The inverse problem	139	(1)
Regional fields and residual anomalies	139	(1)
Direct interpretation	140	(2)
Indirect interpretation	142	(2)
Elementary potential theory and potential field manipulation	144	(3)
Applications of gravity surveying	147	(8)
Problems	150	(3)
Further reading	153	(2)
Magnetic surveying	155	(28)
Introduction	155	(1)
Basic concepts	155	(3)
Rock magnetism	158	(1)
The geomagnetic field	159	(1)
Magnetic anomalies	160	(2)
Magnetic surveying instruments	162	(2)
Introduction	162	(1)
Fluxgate magnetometer	162	(1)
Proton magnetometer	163	(1)
Optically pumped magnetometer	164	(1)
Magnetic gradiometers	164	(1)
Ground magnetic surveys	164	(1)
Aeromagnetic and marine surveys	164	(1)
Reduction of magnetic observations	165	(1)
Diurnal variation correction	165	(1)
Geomagnetic correction	166	(1)
Elevation and terrain corrections	166	(1)
Interpretation of magnetic anomalies	166	(6)
Introduction	166	(2)
Direct interpretation	168	(2)
Indirect interpretation	170	(2)
Potential field transformations	172	(1)
Applications of magnetic surveying	173	(10)
Problems	180	(1)
Further reading	181	(2)
Electrical surveying	183	(25)
Introduction	183	(1)
Resistivity method	183	(16)
Introduction	183	(1)
Resistivities of rocks and minerals	183	(1)
Current flow in the ground	184	(2)
Electrode spreads	186	(1)
Resistivity surveying equipment	186	(1)
Interpretation of resistivity data	187	(1)
Vertical electrical sounding interpretation	188	(5)
Constant separation traversing interpretation	193	(3)
Limitations of the resistivity method	196	(1)
Applications of resistivity surveying	196	(3)
Induced polarization (IP) method	199	(4)
Principles	199	(1)
Mechanisms of induced polarization	199	(1)
Induced polarization measurements	200	(1)
Field operations	201	(1)
Interpretation of induced polarization data	201	(1)
Applications of induced polarization surveying	202	(1)
Self potential (SP) method	203	(5)
Introduction	203	(1)
Mechanism of self-potential	203	(1)
Self-potential equipment and survey procedure	203	(1)
Interpretation of self-potential anomalies	204	(1)
Problems	205	(2)
Further reading	207	(1)
Electromagnetic surveying	208	(23)
Introduction	208	(1)
Depth of penetration of electromagnetic fields	208	(1)
Detection of electromagnetic fields	209	(1)
Tilt-angle methods	209	(3)
Tilt-angle methods employing local transmitters	210	(1)
The VLF method	210	(2)
The AFMAG method	212	(1)
Phase measuring systems	212	(2)
Time-domain electromagnetic surveying	214	(2)
Non-contacting conductivity measurement	216	(2)
Airborne electromagnetic surveying	218	(3)
Fixed separation systems	218	(2)
Quadrature systems	220	(1)
Interpretation of electromagnetic data	221	(1)
Limitations of the electromagnetic method	221	(1)
Telluric and magnetotelluric field methods	221	(4)
Introduction	221	(1)
Surveying with telluric currents	222	(2)
Magnetotelluric surveying	224	(1)
Ground-penetrating radar	225	(2)
Applications of electromagnetic surveying	227	(4)
Problems	228	(2)
Further reading	230	(1)
Radiometric surveying	231	(5)
Introduction	231	(1)
Radioactive decay	231	(1)
Radioactive minerals	232	(1)
Instruments for measuring radioactivity	233	(2)
Geiger counter	233	(1)
Scintillation counter	233	(1)
Gamma-ray spectrometer	233	(1)
Radon emanometer	234	(1)
Field surveys	235	(1)
Example of radiometric surveying	235	(1)
Further reading	235	(1)
Geophysical borehole logging	236	(14)
Introduction to drilling	236	(1)
Principles of well logging	236	(1)
Formation evaluation	237	(1)
Resistivity logging	237	(6)
Normal log	238	(1)
Lateral log	239	(1)
Laterolog	240	(1)
Microlog	241	(1)
Porosity estimation	241	(1)
Water and hydrocarbon saturation estimation	241	(1)
Permeability estimation	242	(1)
Resistivity dipmeter log	242	(1)
Induction logging	243	(1)
Self potential logging	243	(1)
Radiometric logging	244	(2)
Natural gamma radiation log	244	(1)
Gamma-ray density log	244	(1)
Neutron-gamma-ray log	245	(1)
Sonic logging	246	(1)
Temperature logging	247	(1)
Magnetic logging	247	(1)
Magnetic log	247	(1)
Nuclear magnetic resonance log	247	(1)
Gravity logging	247	(3)
Problems	248	(1)
Further reading	249	(1)
Appendix: SI, c.g.s. and Imperial (customary USA)-units and conversion factors	250	(1)
References	251	(6)
Index	257