Planning Land 3-D Seismic Surveys

Transcription

1 Planning Land 3-D Seismic Surveys Andreas Cordsen, Mike Galbraith, and John Peirce Edited by Bob A. Hardage Series Editor: Stephen J. Hill Geophysical Developments Series No. 9 Society of Exploration Geophysicists

2 Table of Contents CHAPTER 1 INITIAL CONSIDERATIONS 1.1 Management Attitudes Objectives Industry Trends Financial Issues Target Horizons Sequence of Events for Data Acquisition Environment and Weather Special Considerations of 3-D versus 2-D Data Acquisition Definitions of 3-D Terms 8 Chapter 1 Quiz 12 CHAPTER 2 PLANNING AND DESIGN 2.1 Survey Design Decision Table Orthogonal Geometry Fold In-line Fold Cross-line Fold Total Fold Fold Taper Signal-to-Noise Ratio (S/N) Bin Size Target Size Maximum Unaliased Frequency Lateral Resolution Lateral Resolution after Migration Separation of Diffractions Vertical Resolution 27 Let's Design a 3-D Part X min X max Target Depth Direct Wave Interference Refracted Wave Interference (First Breaks) Deep Horizon Critical Reflection Offset Maximum NMO Stretch to Be Allowed Required Offset to Measure Deepest LVL (refractor) Required NMO Discrimination Multiple Cancellation Offsets Necessary for AVO Dip Measurements 35 vii

3 viii Table of Contents Let's Design a 3-D Part 2 36 Chapter 2 Quiz 37 CHAPTER 3 PATCHES AND EDGE MANAGEMENT 3.1 Offset Distribution Azimuth Distribution Narrow versus Wide Azimuth Surveys % Rule Fresnel Zone Diffractions Migration Apron Edge Management Ray-Trace Modeling Record Length 51 Let's Design a 3-D - Part 3 53 Let's Design a 3-D - Summary 54 Chapter 3 Quiz 55 CHAPTER 4 FLOWCHARTS, EQUATIONS, AND SPREADSHEETS D Design Flowchart Basic 3-D Equations Square Bins Basic 3-D Equations Rectangular Bins Basic Steps in 3-D Layout Five-Step Method Graphical Approach Standardized Spreadsheets Estimating the Cost of a 3-D Survey Cost Model 69 CHAPTER 5 FIELD LAYOUTS 5.1 Full-Fold 3-D Sampling the 5-D Prestack Wavefield Swath Orthogonal Brick Nonorthogonal Flexi-Bin or Bin Fractionation Button Patch Zig-Zag Mega-Bin Hexagonal Binning Star 96

4 Table of Contents ix 5.13 Radial Random Circular Patch Nominal Fold Comparison 99 Chapter 5 Quiz 105 CHAPTER 6 SOURCE EQUIPMENT 6.1 Explosive Sources Dynamite Testing Dynamite Shooting Strategy Vibrators Vibrator Array Concepts Vibrator Testing Vibrator Deployment Strategy Other Sources 119 Chapter 6 Quiz 119 CHAPTER 7 RECORDING EQUIPMENT 7.1 Receivers Recorders Distributed Systems Telemetry Systems Remote Storage 127 Chapter 7 Quiz 127 CHAPTER 8 ARRAYS 8.1 The Question of Arrays Geophone Arrays Source Arrays Combined Array Response Stack Arrays Hands-Off Acquisition Technique Symmetric Sampling 134 CHAPTER 9 PRACTICAL FIELD CONSIDERATIONS 9.1 Surveying Script Files Templates Roll-On/Off 141

5 x Table of Contents 9.5 No Roll-On/Off Swath Width Shooting Strategy Vibrator Dynamite Large Surveys Field Visits (QC) Offsets and Skids General Considerations Imaging Area Cables Permitting Safety Field Examples Field QC (Data) Positional Data Quality Seismic Data Quality Verify Seismic/Positional Data Relationship 153 Chapter 9 Quiz 155 CHAPTER 10 PROCESSING 10.1 Processing Processing Stream Refraction Statics Velocity Analysis Reflection Statics Dip Moveout Stack Acquisition Footprints Migration and Random Sampling Making Adjustments for Data Quality 168 Chapter 10 Quiz 169 CHAPTER 11 INTERPRETATION 11.1 Interpretation Systems Mapping Integration Acquisition Footprints Seismic Attributes Geostatistics Immersion Technology 173

6 Table of Contents xi CHAPTER 12 SPECIAL INTEREST TOPICS 12.1 Digital Orthomaps and GIS data Transition Zones Presstack Time and Depth Migration Time-Lapse (4-D) Seismic Converted Wave 3-D Design D Inversions Future Directions 181 ANSWERS TO QUIZ QUESTIONS 183 GLOSSARY 185 REFERENCES 195 INDEX 201