Applied High-Resolution Geophysical Methods: Offshore Geoengineering Hazards

273 Pages·1984·11.172 MB·English

by  Peter K. Trabant Ph.D. (auth.)

APPLIED HIGH-RESOLUTION
GEOPHYSICAL METHODS
Offshore Geoengineering Hazards

APPLIED HIGH-RESOLUTION
GEOPHYSICAL METHODS
Offshore Geoengineering Hazards
Peter K. Trabant, Ph.D.
M
Springer-Science+ Business Media, B. V.
©Springer Science+Business Media Dordrecht 1984
Originally published by International Human Resources Development Corporation in 1984
Softcover reprint of the bardeover 1st edition 1984
All rights reserved. No part of this
book may be used or reproduced in any manner whatsoever
without written permission of the publisher except in the case
of brief quotations embodied in critical articles and reviews.
For information address: IHRDC, Publishers, 137 Newbury
Street, Boston, MA 02116.
Library of Congress Cataloging in Publication Data
Trabant, Peter K., 1942-
Applied high-resolution geophysical methods.
lncludes bibliographical references and index.
1. Echo sounding. 2. Offshore structures-Safety measures.
3. Drilling platforms-Safety measures. 4. Engineering
geology-Safety measures. I. Title. GC78.E3T7 1984
627'.9 83-26662
ISBN 978-94-009-6495-2 ISBN 978-94-009-6493-8 (eBook)
DOI 10.1007/978-94-009-6493-8
Frontispiece: "Artist's Conception of the Mid-Pacific
Mountains." From Hamilton, E.L., 1956, Sunken islands of
the mid-Pacific mountains: Geol. Soc. Am., Memoir no. 64,
plate 1, 97 p. Reprinted by permission. Oil painting by
Chesley Bonestell.
Dedicated to the memories of Dave Harvey, Joe Gray,
and Ken Cram
CONTENTS
ACKNOWLEDGMENTS xiii
Chapter One
INTRODUCTION 1
Historical Background 2
Echo Sounders 3
High-Resolution Profilers 5
Side-Scan Sonars 5
~agnetometers 6
Geoengineering Surveys 7
Typical Survey 7
Text Organization 9
Chapter Two
MARINE GEOPHYSICS: AN OVERVIEW 11
Propagation of Seismic W aves 11
Types of Seismic W aves 11
Compressional Waves 11
Shear Waves 12
Wave Path Theory 12
Reflections 14
Geometry of Reflection Paths 15
Absorption and Attenuation 16
Wide-Angle Reflection and Refraction 16
Seismic Velocities 18
Resolution and Frequency 19
Diffractions and Other Unwanted Signals 20
Diffractions 21
Water Surface Echoes or Ghosts 21
Direct Arrival 21
Side Echoes 21
Multiples 22
Enhancement of Seismic Reflection Data 22
Principles of Seismic Interpretation 23
Correlation of Reflectors 24
Geoengineering Hazards 24
Chapter Three
MARINE GEOTECHNIQUE, AN OVERVIEW 25
Sediment-Structure Interrelations 25
Design Considerations 25
Basis for Sediment Sampling 26
Sampling Methods 26
Sediment Sampies 26
vii
viii
Geotechnical Analyses 26
Soil or Sediment "Index Properties" 27
Visual Description 27
Odor 29
Mineralogie Composition 29
Grain Size Analyses 29
Bulk Physical Properties 30
Atterberg Limits 31
Strength of Sediments 31
Shear Strength 31
Direct Shear Test 36
Consolidation Tests 36
Acoustic Velocities 39
Triaxial Compression Testing 39
In-Place Testing of Sediments 39
Pressurized Sampies 39
Classification of Marine Sediments 41
Future Developments 41
Design Applications 41
Geoengineering Surveys 42
Chapter Four
ECHO SOUNDERS 43
Introduction 43
Transmission of Sound in Water 43
Speed of Sound 45
Principle of Operation (Analog Systems) 48
Principle of Operation (Digital Systems) 50
Resolution of Echo Sounders 50
Recorder Precision 50
Motion Compensators 51
Multiple Beam Systems 52
Deep-Tow Systems 55
Computer Processing 56
Operations and Calibration 57
Interpretation 58
Chapter Five
SIDE SCAN SONAR 61
Introduction 61
Applications 61
Principles of Operation 61
Resolution 63
Contents ix
Side Scan Sonar Systems 65
Deep-Tow Systems 68
Digital Operation 72
Operational Procedures 72
Tow Methods 72
Interpretation 7 4
Chapter Six
SUBBOTTOM PROFILERS 81
Introduction 81
Historical Background 81
Applications 81
Principle of Operation 84
Operation 85
Digital Operation 86
Operational Adjustments 87
Variable Frequency Units 88
Heave Compensators 90
Deep-Tow Systems 90
Resolution 92
Interpretation 95
Chapter Seven
SEISMIC SOURCES 101
Introduction 101
Sparkers 101
Air Guns 107
Water Guns 109
Miniflexichoc 110
Minisleeve Exploder 110
General Operational Considerations 115
Chapter Eight
SINGLE CHANNEL SEISMIC REFLECTION SYSTEMS 117
Introduction 117
Hydrophone Receivers 117
Analog Signal Processing 118
Analog Recorders 119
Real-Time Digital Signal Processing 124
Operational Considerations 124
Interpretation 12 7
X
Chapter Nine
MULTIFOLD ACQUISITION AND DIGITAL PROCESSING 131
Multifold Seismic Receiver Arrays 131
Hydrophone Cables 131
Hydrophone Group Geometry 131
Hydrophone Streamer Depth 133
Digital Hydrophone Cables 134
Digital Data Acquisition and Storage 134
Digital Sampling 135
Processing of Multifold Digital Seismic Data 139
Data Processing 139
Operational Considerations 161
Interpretation 164
Conclusions and Future Trends 164
Chapter Ten
MARINE MAGNETOMETERS 167
lntroduction 167
Historical Background 167
The Earth's Magnetic Field 167
Principle of Operation 173
Operation 173
Gradiometers 176
Interpretation 176
Operation and Calibration 178
Chapter Eleven
MARINE GEOENGINEERING HAZARDS 181
Case Studies and Interpretation 181
Geoengineering Hazards 181
Interpretation Sequence 183
Geoengineering Survey Objectives 185
Case Study 1: Pipeline Pre-Lay Survey 185
Case Study 2: A Structural Puzzle 192
Case Study 3: Anatomy of a Blowout 196
Case Study 4: Deltaic Mud Flows 199
Seismic Interpretation 206
Sea Level Fluctuations 206
Chapter Twelve
SURVEY ORGANIZATION, NAVIGATION,
AND FUTURE DEVELOPMENTS 213
Survey Organization 213
Survey Objectives 213