Advances in Oil and Gas Exploration &Production

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The book series Advances in Oil and Gas Exploration & Production pub-lishes scientific monographs on a broad range of topics concerning geo-physical and geological research on conventional and unconventional oil andgas systems, and approaching those topics from both an exploration and aproduction standpoint. The series is intended to form a diverse library ofreference works by describing the current state of research on selectedthemes, such as certain techniques used in the petroleum geoscience businessor regional aspects. All books in the series are written and edited by leadingexperts actively engaged in the respective field.

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Hamid N. Alsadi

Seismic HydrocarbonExploration2D and 3D Techniques

123

Hamid N. AlsadiData Processing SectionMinistry of OilBaghdadIraq

ISSN 2509-372X ISSN 2509-3738 (electronic)Advances in Oil and Gas Exploration & ProductionISBN 978-3-319-40435-6 ISBN 978-3-319-40436-3 (eBook)DOI 10.1007/978-3-319-40436-3

Library of Congress Control Number: 2016942906

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Preface

The favorable reception of the first edition of this book (seismic Exploration,published by Birkhauser Verlag in 1980) stimulated my belief in the need ofan updated book that includes the advances in the techniques which havetaken place during the past three decades. In preparing the present updatedvolume, I have taken into consideration the remarks and suggestions of theusers of the 1980 edition from both of the academic and industrial workdomains.

Since 1980, when the first edition of this book was published, greatdevelopments in the seismic exploration technology have taken place. Thesedevelopments have occurred in all of the three exploration phases: acquisi-tion, processing, and interpretation techniques. The most prominent advanceswhich have taken place in these years are the widespread implementationsof the 3D surveying, pre-stack migration, and growing interpretation tech-niques in both structural and stratigraphic exploration. As it is familiar withthe exploration geophysicists, this subject (seismic exploration) is fully dealtwith in many original and authentic internationally known text books. In thispublication, no new subjects added to those found in the other standard bookswhich are well known in the geophysical library. In fact, these and otherrelated scientific papers and research reports formed solid references for thepresent book. There are, however, differences in the design and presentationapproach.

In its design, the book is intended to be a comprehensive treatise of theseismic exploration tool, addressing audiences in both of the academic andindustrial establishments. It is made up of 12 chapters covering the basicaspects of the seismic reflection exploration subject, starting with the basictheory, followed by the applied data acquisition technology, and ending withthe processing and interpretation. In presenting the subject matter, emphasisis made on the practical aspects of the subject, using clear and simplifiedpresentation, avoiding excessive descriptions and unnecessary lengthycomments. Numerous illustration figures (>390 figures) have been usedthroughout the book to aid in clarifying the concepts and procedures involvedin any standard seismic exploration survey. In this way, the book can beconsidered as a very useful introductory teaching manual for universitystudents taking seismic reflection exploration as part of a postgraduatecourse.

v

The chapters of the book are sequenced in the order of the activitiesnormally executed in a standard seismic exploration survey: field acquisition,processing, and interpretation. Chapter 1 is an introductory chapter in whicha brief historical note and short review of the geophysical explorationmethods are given. This is followed by four chapters covering the theoreticalaspect of the subject including basic principles and definitions of seismicwaves, with a special chapter assigned for the seismic wave propagationvelocity. The propagation phenomena, reflection, diffraction, transmission,and refraction, are dealt with in Chaps. 4 and 5. The following two chaptersare devoted to the two main tools applied in seismic exploration, namely the2D and 3D surveying techniques.

Due to its important role in understanding of the processing steps applied inseismic data processing, a chapter (Chap. 8) is assigned solely for the seismicsignal. This chapter is structured on the theme of considering the seismicreflection wavelet as a propagating signal in the same way as the electro-magnetic signal is treated by the communication theory applied in electro-magnetic wave propagation. Including a chapter on seismic signals, precedingthe processing chapters, is a feature by which this book has deviated fromother conventional publications. Data processing is presented under twoheadings: processing tools (Chap. 9) and the normally applied processingsequence (Chap. 10). Chapter 11 covers some specialized seismic explorationtools sometimes used in support of the conventional seismic reflection andrefraction surveying. The book is concluded with Chap. 12 on interpretation.

I would like to express my gratitude to my wife Asira and my sons (Eng.Majid, Ph.D., Eng. Muhannad, M.Sc., Thurayah, B.Sc., and Eng. Mahir,B.Sc.), for their continuous support and help throughout the past three years.My work in the writing of the book has incurred an additional burden to thefamily especially during the abnormally difficult times, which our countryhas experienced in the past twelve years.

Baghdad, Iraq Hamid N. AlsadiDecember 2015

vi Preface

Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Historical Review . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.1 Elasticity and Seismic Waves (Båth 1979) . . . 11.1.2 Earthquake Seismology (Richter 1958). . . . . . 21.1.3 Exploration Seismology

(Telford et al. 1990) . . . . . . . . . . . . . . . . . . 21.1.4 Summary of Exploration Seismology History

(Sheriff and Geldart 1995) . . . . . . . . . . . . . . 31.2 The Geophysical Exploration Project . . . . . . . . . . . . . 31.3 Geophysical Exploration Methods . . . . . . . . . . . . . . . 4

1.3.1 The Seismic Method . . . . . . . . . . . . . . . . . . 41.3.2 The Gravity Method . . . . . . . . . . . . . . . . . . 41.3.3 The Magnetic Method . . . . . . . . . . . . . . . . . 61.3.4 The Electical Method. . . . . . . . . . . . . . . . . . 71.3.5 The Radioactivity Method . . . . . . . . . . . . . . 9

1.4 Oil Well Drilling. . . . . . . . . . . . . . . . . . . . . . . . . . . 91.4.1 Drilling of the Exploration-Well . . . . . . . . . . 101.4.2 The Oil-Well Rotary Drilling . . . . . . . . . . . . 101.4.3 The Drill-Hole and Well Casing . . . . . . . . . . 11

1.5 Well Geophysical Logging . . . . . . . . . . . . . . . . . . . . 111.5.1 Electrical Logging . . . . . . . . . . . . . . . . . . . . 121.5.2 Radioactivity Logging . . . . . . . . . . . . . . . . . 141.5.3 Acoustic Logging . . . . . . . . . . . . . . . . . . . . 161.5.4 Log Interpretation . . . . . . . . . . . . . . . . . . . . 19

1.6 Latest Developments in Well Logging . . . . . . . . . . . . 191.6.1 Logging While Drilling Technique . . . . . . . . 201.6.2 Borehole Imaging Tools. . . . . . . . . . . . . . . . 20

1.7 Well Completion . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2 Seismic Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.1 The Fundamental Conditions . . . . . . . . . . . . . . . . . . 232.2 Theory of Elasticity . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.2.1 Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242.2.2 Strain . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262.2.3 Common Types of Strain . . . . . . . . . . . . . . . 262.2.4 The Volume-Changing Strain . . . . . . . . . . . . 272.2.5 The Shape-Changing Strain . . . . . . . . . . . . . 282.2.6 The Cubical Dilatation . . . . . . . . . . . . . . . . . 28

vii

2.2.7 Stress-Strain Relationship . . . . . . . . . . . . . . . 292.2.8 Hooke’s Law for Isotropic Media . . . . . . . . . 292.2.9 The Elastic Moduli . . . . . . . . . . . . . . . . . . . 302.2.10 The Elastic Moduli Interrelationships . . . . . . . 32

2.3 Wave Motion Equation . . . . . . . . . . . . . . . . . . . . . . 322.3.1 One-Dimensional Scalar Wave Equation . . . . 332.3.2 The Scalar and Vector 3D Wave

Equations . . . . . . . . . . . . . . . . . . . . . . . . . . 342.3.3 Plane Waves. . . . . . . . . . . . . . . . . . . . . . . . 352.3.4 The P- and S-Waves . . . . . . . . . . . . . . . . . . 36

2.4 Classification of Common Elastic Waves . . . . . . . . . . 362.4.1 Body Waves. . . . . . . . . . . . . . . . . . . . . . . . 372.4.2 Surface Waves . . . . . . . . . . . . . . . . . . . . . . 382.4.3 Seismic Noise. . . . . . . . . . . . . . . . . . . . . . . 39

2.5 Propagation of Seismic Waves . . . . . . . . . . . . . . . . . 402.5.1 Elements of the Seismic Field. . . . . . . . . . . . 412.5.2 Concepts of Wave-Fronts and Rays . . . . . . . . 412.5.3 Huygens’ Principle . . . . . . . . . . . . . . . . . . . 422.5.4 The Concept of the Interface . . . . . . . . . . . . 422.5.5 Changes of Propagation Direction at

Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . 432.5.6 Wave Conversion at Interfaces . . . . . . . . . . . 442.5.7 Energy Partitioning and Zoeppritz

Equations . . . . . . . . . . . . . . . . . . . . . . . . . . 452.5.8 Amplitude Variation with Angle

of Incidence . . . . . . . . . . . . . . . . . . . . . . . . 462.6 Effect of the Medium on Wave Energy . . . . . . . . . . . 46

2.6.1 Geometrical Spreading . . . . . . . . . . . . . . . . . 472.6.2 Inelastic Attenuation . . . . . . . . . . . . . . . . . . 482.6.3 Seismic Wave Energy Measurement

and the DB Unit . . . . . . . . . . . . . . . . . . . . . 492.6.4 The Logarithmic Decrement . . . . . . . . . . . . . 492.6.5 Wave Dispersion. . . . . . . . . . . . . . . . . . . . . 49

3 The Seismic Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533.2 Factors Influencing Seismic Velocity . . . . . . . . . . . . . 53

3.2.1 Lithology Effect . . . . . . . . . . . . . . . . . . . . . 533.2.2 Elasticity and Density Effects . . . . . . . . . . . . 543.2.3 Porosity and Saturation Fluid Effects . . . . . . . 543.2.4 Depth and Geological Age Effects. . . . . . . . . 563.2.5 Overburden Pressure Effect . . . . . . . . . . . . . 563.2.6 Other Velocity-Affecting Factors . . . . . . . . . . 57

3.3 The Velocity Function . . . . . . . . . . . . . . . . . . . . . . . 583.4 Types of Velocity Functions . . . . . . . . . . . . . . . . . . . 59

3.4.1 Instantaneous Velocity . . . . . . . . . . . . . . . . . 593.4.2 Interval Velocity . . . . . . . . . . . . . . . . . . . . . 603.4.3 Average Velocity . . . . . . . . . . . . . . . . . . . . 603.4.4 Root Mean Square Velocity . . . . . . . . . . . . . 613.4.5 Stacking Velocity . . . . . . . . . . . . . . . . . . . . 62

viii Contents

3.4.6 The Apparent Velocity. . . . . . . . . . . . . . . . . 633.4.7 The Group and Phase Velocities . . . . . . . . . . 643.4.8 Representations of the Velocity Functions . . . 64

3.5 Velocity Determination Methods . . . . . . . . . . . . . . . . 643.5.1 The Well Velocity Survey . . . . . . . . . . . . . . 653.5.2 The Up-Hole Velocity Survey. . . . . . . . . . . . 663.5.3 Continuous Velocity Logging . . . . . . . . . . . . 663.5.4 (X2 − T2 Method) . . . . . . . . . . . . . . . . . . . . 673.5.5 (T − ΔT) Method . . . . . . . . . . . . . . . . . . . . 673.5.6 Velocity Analysis Method . . . . . . . . . . . . . . 683.5.7 Seismic Velocity Inversion . . . . . . . . . . . . . . 69

3.6 Uses of the Seismic Velocity Data. . . . . . . . . . . . . . . 69

4 Seismic Wave Reflection and Diffraction . . . . . . . . . . . . . . 714.1 The Commonly-Recorded Seismic Events . . . . . . . . . 714.2 Wave Changes at Reflection Interface . . . . . . . . . . . . 71

4.2.1 Reflection Coefficient at InclinedIncidence . . . . . . . . . . . . . . . . . . . . . . . . . . 72

4.2.2 Reflection Coefficient at Normal Incidence. . . 734.2.3 Geometry of Reflection from Dipping

Reflectors. . . . . . . . . . . . . . . . . . . . . . . . . . 744.2.4 Geometry of Reflection from Horizontal

Reflectors. . . . . . . . . . . . . . . . . . . . . . . . . . 754.2.5 Reflection from Multiple Reflectors . . . . . . . . 75

4.3 The NMO and DMO Concepts . . . . . . . . . . . . . . . . . 764.3.1 The Normal Move-Out (NMO) Concept. . . . . 764.3.2 The Dip Move-Out (DMO) Concept . . . . . . . 79

4.4 The CDP, CRP, and CMP Concepts . . . . . . . . . . . . . 794.4.1 CDP, CRP, and CMP in Case

of Horizontal Reflector . . . . . . . . . . . . . . . . 804.4.2 CDP, CRP, and CMP in Case of Dipping

Reflector . . . . . . . . . . . . . . . . . . . . . . . . . . 804.5 The Seismic Wave Diffraction . . . . . . . . . . . . . . . . . 81

4.5.1 The Point-Diffractor . . . . . . . . . . . . . . . . . . 824.5.2 Diffraction from Terminating Reflectors . . . . . 834.5.3 Diffraction Seismic Image . . . . . . . . . . . . . . 834.5.4 Diffraction Travel-Time Function . . . . . . . . . 844.5.5 The Diffraction Hyperbola . . . . . . . . . . . . . . 854.5.6 Distortion Effects of Diffraction . . . . . . . . . . 864.5.7 The Exploding-Reflector Model . . . . . . . . . . 86

5 Seismic Wave Transmission and Refraction . . . . . . . . . . . . 895.1 Seismic Wave Transmission . . . . . . . . . . . . . . . . . . . 89

5.1.1 Transmission Coefficient at NormalIncidence . . . . . . . . . . . . . . . . . . . . . . . . . . 89

5.1.2 The Two-Way Transmission Coefficient. . . . . 905.1.3 Attenuation Due to Reflection

and Transmission . . . . . . . . . . . . . . . . . . . . 905.1.4 Role of Transmission in Seismic

Exploration. . . . . . . . . . . . . . . . . . . . . . . . . 91

Contents ix

5.2 Seismic Wave Refraction . . . . . . . . . . . . . . . . . . . . . 925.2.1 Snell’s Law of Refraction. . . . . . . . . . . . . . . 925.2.2 The Critical Refraction

and Head Wave Generation . . . . . . . . . . . . . 955.2.3 Ray-Path Geometry and Travel-Time

Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . 965.2.4 Refraction Travel-Time Function. . . . . . . . . . 965.2.5 The Delay-Time Concept . . . . . . . . . . . . . . . 985.2.6 Refraction in a Multi-layer Medium. . . . . . . . 995.2.7 Refraction in a Medium of Linear

Velocity Variation . . . . . . . . . . . . . . . . . . . . 995.2.8 Refraction from a Faulted Refractor. . . . . . . . 1005.2.9 Applications of Seismic Wave Refraction. . . . 100

6 2D Seismic Reflection Surveying . . . . . . . . . . . . . . . . . . . . 1056.1 Reflection Surveying Concepts . . . . . . . . . . . . . . . . . 105

6.1.1 The Spread Configuration . . . . . . . . . . . . . . 1056.1.2 The Seismic Trace. . . . . . . . . . . . . . . . . . . . 1066.1.3 The Shotpoint . . . . . . . . . . . . . . . . . . . . . . . 1076.1.4 The Seismic Profiling Technique. . . . . . . . . . 1076.1.5 The Fold of Coverage . . . . . . . . . . . . . . . . . 1086.1.6 The CDP Trace Gather . . . . . . . . . . . . . . . . 110

6.2 Seismic Reflection Data Acquisition . . . . . . . . . . . . . 1136.2.1 Seismic Energy Sources . . . . . . . . . . . . . . . . 1136.2.2 Seismic Detectors . . . . . . . . . . . . . . . . . . . . 1196.2.3 The Seismic Data Recording. . . . . . . . . . . . . 1216.2.4 Data Playback and Display. . . . . . . . . . . . . . 126

6.3 Seismic Noise Characterization and Attenuation . . . . . 1266.3.1 Random Noise Attenuation. . . . . . . . . . . . . . 1276.3.2 Coherent Noise Attenuation . . . . . . . . . . . . . 127

6.4 Field Measures for Signal Enhancement . . . . . . . . . . . 1316.4.1 The Noise Test . . . . . . . . . . . . . . . . . . . . . . 1316.4.2 The Experimental Shooting . . . . . . . . . . . . . 1346.4.3 Determination of the LVL Properties . . . . . . . 134

6.5 The Seismic Field Crew. . . . . . . . . . . . . . . . . . . . . . 136

7 3D Seismic Reflection Surveying . . . . . . . . . . . . . . . . . . . . 1397.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

7.1.1 Nature Is Three Dimensional . . . . . . . . . . . . 1397.1.2 1D-2D-3D Terminology . . . . . . . . . . . . . . . . 1407.1.3 Limitations of 2D Seismic Surveying. . . . . . . 1417.1.4 Merits of the 3D Technique . . . . . . . . . . . . . 1437.1.5 Survey Preplanning . . . . . . . . . . . . . . . . . . . 1467.1.6 Cost Considerations of 3D Surveys . . . . . . . . 146

7.2 Definitions and Basic Principles . . . . . . . . . . . . . . . . 1487.2.1 Definition of 3D Surveying . . . . . . . . . . . . . 1487.2.2 The 3D Spread-Geometry. . . . . . . . . . . . . . . 1497.2.3 Concept of the Trace Azimuth . . . . . . . . . . . 149

x Contents

7.2.4 The CDP Bin and Bin Attributes. . . . . . . . . . 1507.2.5 The Surface and Sub-surface Coverage . . . . . 1507.2.6 The Seismic Data Volume . . . . . . . . . . . . . . 151

7.3 3D Field Data Acquisition . . . . . . . . . . . . . . . . . . . . 1537.3.1 Types of Marine 3D Spreads . . . . . . . . . . . . 1537.3.2 Types of Land 3D Spreads . . . . . . . . . . . . . . 1557.3.3 The Swath Shooting Technique. . . . . . . . . . . 1567.3.4 Types of Templates Used in Swath

Shooting . . . . . . . . . . . . . . . . . . . . . . . . . . 1567.3.5 The Loop Shooting Technique . . . . . . . . . . . 1597.3.6 The 3D Survey Design . . . . . . . . . . . . . . . . 159

7.4 Processing of 3D Data . . . . . . . . . . . . . . . . . . . . . . . 1647.4.1 The Field Data Processing . . . . . . . . . . . . . . 1667.4.2 The Final Data Processing . . . . . . . . . . . . . . 1667.4.3 3D Data Displays . . . . . . . . . . . . . . . . . . . . 166

8 The Seismic Reflection Signal . . . . . . . . . . . . . . . . . . . . . . 1698.1 Definition of the Seismic Signal . . . . . . . . . . . . . . . . 169

8.1.1 The Seismic Signal Parameters . . . . . . . . . . . 1708.1.2 The Seismic Signal Spectrum . . . . . . . . . . . . 1708.1.3 Comparison with the Radar Signal . . . . . . . . 1728.1.4 The Seismic Reflection-Signal Changes . . . . . 172

8.2 The Seismic Trace. . . . . . . . . . . . . . . . . . . . . . . . . . 1738.2.1 The Convolutional Model of the Seismic

Trace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1748.2.2 The Synthetic Seismogram . . . . . . . . . . . . . . 1758.2.3 The Digital Seismic Trace . . . . . . . . . . . . . . 176

8.3 The Wavelet Concept . . . . . . . . . . . . . . . . . . . . . . . 1778.3.1 Definition of the Seismic Wavelet . . . . . . . . . 1778.3.2 Energy and Delay Properties of Wavelets. . . . 178

8.4 Sampling and the Digital Function . . . . . . . . . . . . . . 1788.4.1 The Digital Function . . . . . . . . . . . . . . . . . . 1798.4.2 The Sampling Process . . . . . . . . . . . . . . . . . 1798.4.3 Representation Methods of the Digital

Function . . . . . . . . . . . . . . . . . . . . . . . . . . 1808.5 The Sampling Theorem and Aliasing . . . . . . . . . . . . . 181

8.5.1 The Sampling Theorem . . . . . . . . . . . . . . . . 1818.5.2 The Aliasing Phenomenon . . . . . . . . . . . . . . 1828.5.3 The Aliasing Frequency Computation . . . . . . 1838.5.4 Effect of Sampling on Signal Spectrum . . . . . 1858.5.5 Aliasing in the Frequency Domain . . . . . . . . 1858.5.6 The Remedy for the Aliasing Effect . . . . . . . 186

8.6 Signal Resolution and Resolution Power . . . . . . . . . . 1878.6.1 Vertical Resolution of Seismic Signals. . . . . . 1878.6.2 Horizontal Resolution of Seismic Signals . . . . 1898.6.3 Fresnel Zone Formula . . . . . . . . . . . . . . . . . 189

Contents xi

8.7 The Common Numbering Systems . . . . . . . . . . . . . . 1908.7.1 Numbering System Concept . . . . . . . . . . . . . 1918.7.2 Applications of the Concept . . . . . . . . . . . . . 1918.7.3 Counting in the Different Numbering

Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

9 The Seismic Processing Tools . . . . . . . . . . . . . . . . . . . . . . 1979.1 The Seismic Processing Tools. . . . . . . . . . . . . . . . . . 197

9.1.1 The Sine Function . . . . . . . . . . . . . . . . . . . . 1979.1.2 The Degrees-Radians Relationship. . . . . . . . . 1989.1.3 Parameters of the Sine Function . . . . . . . . . . 1989.1.4 The Frequency Concept . . . . . . . . . . . . . . . . 1999.1.5 The Phase Concept . . . . . . . . . . . . . . . . . . . 2009.1.6 Temporal and Spatial Frequencies . . . . . . . . . 2009.1.7 Propagating Sine Wave . . . . . . . . . . . . . . . . 202

9.2 Fourier Analysis and Concept of Spectra . . . . . . . . . . 2039.2.1 Fourier Series . . . . . . . . . . . . . . . . . . . . . . . 2039.2.2 Gibbs’ Phenomenon . . . . . . . . . . . . . . . . . . 2059.2.3 Fourier Transform . . . . . . . . . . . . . . . . . . . . 205

9.3 Concept of the Frequency Spectrum . . . . . . . . . . . . . 2069.3.1 The Line Spectrum . . . . . . . . . . . . . . . . . . . 2079.3.2 The Continuous Spectrum . . . . . . . . . . . . . . 2079.3.3 The Fourier Power Spectrum . . . . . . . . . . . . 2079.3.4 The Two-Domain Concept . . . . . . . . . . . . . . 2089.3.5 Spectrum of the Rectangular Pulse . . . . . . . . 2099.3.6 Spectrum of the Spike Pulse . . . . . . . . . . . . . 2109.3.7 The Dirac-Delta Function . . . . . . . . . . . . . . . 2109.3.8 Frequency Limits of Fourier Spectra . . . . . . . 211

9.4 The Phase Spectrum . . . . . . . . . . . . . . . . . . . . . . . . 2129.4.1 The Zero-Phase Spectrum. . . . . . . . . . . . . . . 2129.4.2 The Linear-Phase Spectrum . . . . . . . . . . . . . 2139.4.3 The Constant-Phase Spectrum . . . . . . . . . . . . 213

9.5 Spectra of Observational Data. . . . . . . . . . . . . . . . . . 2149.5.1 Truncation Effect and Windowing . . . . . . . . . 2159.5.2 The Rectangular Window (Box-Car) . . . . . . . 2169.5.3 Triangular Window (Bartlett) . . . . . . . . . . . . 217

9.6 Correlation Functions. . . . . . . . . . . . . . . . . . . . . . . . 2189.6.1 Cross Correlation Function, C12(τ). . . . . . . . . 2189.6.2 Autocorrelation Function C11(τ) . . . . . . . . . . 2189.6.3 Properties and Applications of Correlation

Functions . . . . . . . . . . . . . . . . . . . . . . . . . . 2199.6.4 Correlation Functions in the Frequency

Domain . . . . . . . . . . . . . . . . . . . . . . . . . . . 2199.7 Convolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2209.8 Deconvolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

9.8.1 Deconvolution Main Objectives . . . . . . . . . . 2229.8.2 Spiking (Whitening) Deconvolution. . . . . . . . 2239.8.3 Gapped Deconvolution. . . . . . . . . . . . . . . . . 2249.8.4 Noise Behaviour Under Deconvolution . . . . . 225

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9.9 Frequency Filtering . . . . . . . . . . . . . . . . . . . . . . . . . 2269.9.1 Definition of the Filtering Process . . . . . . . . . 2269.9.2 Role and Objectives of Filtering

in Seismic Exploration . . . . . . . . . . . . . . . . . 2279.9.3 Concept of the Linear System. . . . . . . . . . . . 2289.9.4 The Filter Impulse Response. . . . . . . . . . . . . 2299.9.5 Mechanism of the Filtering Process . . . . . . . . 2309.9.6 Filtering in the Two Domains . . . . . . . . . . . . 2309.9.7 Types of Filters. . . . . . . . . . . . . . . . . . . . . . 2319.9.8 Application of the Band-Pass Filter . . . . . . . . 2319.9.9 Filter Shape (Side-Lobes Problem) . . . . . . . . 2329.9.10 Effect of the Filter Length . . . . . . . . . . . . . . 2339.9.11 Effect of the Filter Spectrum Shape . . . . . . . . 2339.9.12 Minimization of the Truncation Effect . . . . . . 2359.9.13 Filter Normalization. . . . . . . . . . . . . . . . . . . 2359.9.14 Time-Variant Filtering . . . . . . . . . . . . . . . . . 2369.9.15 The Filter Tests. . . . . . . . . . . . . . . . . . . . . . 2379.9.16 Phase Removing Filtering . . . . . . . . . . . . . . 238

9.10 Frequency-Wave Number (FK) Filtering . . . . . . . . . . 2389.10.1 The t-x and F-K Domains . . . . . . . . . . . . . . 2389.10.2 Application of the F-K Filtering . . . . . . . . . . 239

9.11 Seismic Trace Equalization. . . . . . . . . . . . . . . . . . . . 2409.11.1 The Need for Trace Equalization. . . . . . . . . . 2409.11.2 Time-Invariant Equalization . . . . . . . . . . . . . 2429.11.3 Time-Variant Equalization . . . . . . . . . . . . . . 242

9.12 Trace-Samples Manipulations . . . . . . . . . . . . . . . . . . 243

10 Processing of Seismic Reflection Data . . . . . . . . . . . . . . . . 24510.1 General Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 245

10.1.1 Main Processing Objectives . . . . . . . . . . . . . 24610.1.2 Role of Processing in Seismic Exploration . . . 24710.1.3 Main Processing Activities . . . . . . . . . . . . . . 24710.1.4 The Processing Sequence . . . . . . . . . . . . . . . 248

10.2 Data Re-organization . . . . . . . . . . . . . . . . . . . . . . . . 25010.2.1 Seismic Data Copying, Reformatting,

and Loading . . . . . . . . . . . . . . . . . . . . . . . . 25010.2.2 Data De-multiplexing. . . . . . . . . . . . . . . . . . 25010.2.3 Sweep Removal . . . . . . . . . . . . . . . . . . . . . 25110.2.4 Vertical Stacking. . . . . . . . . . . . . . . . . . . . . 25210.2.5 Geometry Data and Field Statics Loading. . . . 25210.2.6 Trace Header Assignment. . . . . . . . . . . . . . . 25310.2.7 Data Re-sampling . . . . . . . . . . . . . . . . . . . . 253

10.3 Pre-stack Processing . . . . . . . . . . . . . . . . . . . . . . . . 25310.3.1 Trace Editing . . . . . . . . . . . . . . . . . . . . . . . 25310.3.2 Noise Attenuation . . . . . . . . . . . . . . . . . . . . 25410.3.3 True Amplitude Recovery . . . . . . . . . . . . . . 25410.3.4 Field Static Correction . . . . . . . . . . . . . . . . . 25610.3.5 Application of Deconvolution . . . . . . . . . . . . 25910.3.6 Trace Equalization. . . . . . . . . . . . . . . . . . . . 26210.3.7 CMP-Sorting . . . . . . . . . . . . . . . . . . . . . . . 263

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10.3.8 NMO Correction . . . . . . . . . . . . . . . . . . . . . 26410.3.9 Trace Muting . . . . . . . . . . . . . . . . . . . . . . . 267

10.4 Stack and Post-stack Processing . . . . . . . . . . . . . . . . 26810.4.1 CMP Stacking of Seismic Traces . . . . . . . . . 26910.4.2 CMP Stacking . . . . . . . . . . . . . . . . . . . . . . 26910.4.3 Vertical Stacking. . . . . . . . . . . . . . . . . . . . . 27010.4.4 Horizontal Stacking . . . . . . . . . . . . . . . . . . . 27010.4.5 Diversity Stacking . . . . . . . . . . . . . . . . . . . . 27110.4.6 The Stack Section . . . . . . . . . . . . . . . . . . . . 271

10.5 Seismic Migration . . . . . . . . . . . . . . . . . . . . . . . . . . 27210.5.1 Distortions in the Stack Section . . . . . . . . . . 27210.5.2 Problem Statement . . . . . . . . . . . . . . . . . . . 27310.5.3 Geometry of the Distortions . . . . . . . . . . . . . 27510.5.4 Relationship of Post-migration Dip

to Pre-migration Dip . . . . . . . . . . . . . . . . . . 27510.5.5 Types of Migration Techniques. . . . . . . . . . . 27610.5.6 Time Versus Depth Migration. . . . . . . . . . . . 28110.5.7 Migration Parameters . . . . . . . . . . . . . . . . . . 28210.5.8 Migration Techniques in Future . . . . . . . . . . 284

10.6 Application of Filtering and Equalization . . . . . . . . . . 28510.6.1 Frequency Filtering . . . . . . . . . . . . . . . . . . . 28510.6.2 Equalization . . . . . . . . . . . . . . . . . . . . . . . . 28510.6.3 Data Storage and Display. . . . . . . . . . . . . . . 286

10.7 Parameter Optimization . . . . . . . . . . . . . . . . . . . . . . 28610.7.1 Velocity Analysis . . . . . . . . . . . . . . . . . . . . 28610.7.2 Residual-Static Analysis . . . . . . . . . . . . . . . . 28710.7.3 Deconvolution Analysis . . . . . . . . . . . . . . . . 28910.7.4 Filter Analysis . . . . . . . . . . . . . . . . . . . . . . 28910.7.5 Equalization Analysis . . . . . . . . . . . . . . . . . 29010.7.6 Mute Analysis . . . . . . . . . . . . . . . . . . . . . . 290

11 Extra Exploration Tools . . . . . . . . . . . . . . . . . . . . . . . . . . 29111.1 Seismic Exploration with S-waves . . . . . . . . . . . . . . . 291

11.1.1 Shear-Waves Generation . . . . . . . . . . . . . . . 29111.1.2 Role of the Shear-Wave Velocity

in Interpretation . . . . . . . . . . . . . . . . . . . . . 29211.2 Vertical Seismic Profiling (VSP) . . . . . . . . . . . . . . . . 292

11.2.1 Field Set-up and Types of VSP. . . . . . . . . . . 29211.2.2 The VSP Field Operation . . . . . . . . . . . . . . . 29311.2.3 The VSP Seismic Record . . . . . . . . . . . . . . . 29311.2.4 The VSP Data Processing . . . . . . . . . . . . . . 294

11.3 Seismic Tomography . . . . . . . . . . . . . . . . . . . . . . . . 29511.3.1 The Forward and Inverse Modeling

Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . 29511.3.2 Types of Seismic Tomography . . . . . . . . . . . 29611.3.3 Interpretation of Tomography Data . . . . . . . . 296

11.4 4D (Time-Lapse) Surveying . . . . . . . . . . . . . . . . . . . 29711.5 Multi-component (3C and 4C) Recording . . . . . . . . . . 29711.6 Passive Seismic Surveying . . . . . . . . . . . . . . . . . . . . 29811.7 Tau-P Transform. . . . . . . . . . . . . . . . . . . . . . . . . . . 298

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11.8 Amplitude Variation with Offset (AVO). . . . . . . . . . . 29911.9 Seismic Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . 299

12 Interpretation of Seismic Reflection Data . . . . . . . . . . . . . . 30112.1 Scope and Objectives. . . . . . . . . . . . . . . . . . . . . . . . 30112.2 The Seismic Interpretation Tools . . . . . . . . . . . . . . . . 30112.3 The Seismic Structural Interpretation . . . . . . . . . . . . . 302

12.3.1 Structural Interpretation Sequence . . . . . . . . . 30212.3.2 The Seismic Structural Features . . . . . . . . . . 304

12.4 The Seismic Stratigraphic Interpretation . . . . . . . . . . . 30612.4.1 Role of the Seismic Wavelet

in Stratigraphic Interpretation . . . . . . . . . . . . 30612.4.2 Basic Stratigraphic Concepts. . . . . . . . . . . . . 30712.4.3 Reflection Configuration Patterns . . . . . . . . . 30812.4.4 Seismo-Stratigraphic Features . . . . . . . . . . . . 31012.4.5 Stratigraphic Interpretation Sequence . . . . . . . 315

12.5 Direct Hydrocarbon Detection and SeismicAttributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31612.5.1 Hydrocarbon Indicators . . . . . . . . . . . . . . . . 31612.5.2 Seismic Attributes . . . . . . . . . . . . . . . . . . . . 317

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325

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