Table Of ContentAdvances in Oil and Gas Exploration & Production
Hamid N. Alsadi
Seismic
Hydrocarbon
Exploration
2D and 3D Techniques
Advances in Oil and Gas Exploration &
Production
Series editor
Rudy Swennen, Department of Earth and Environmental Sciences,
K.U. Leuven, Heverlee, Belgium
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Hamid N. Alsadi
Seismic Hydrocarbon
Exploration
2D and 3D Techniques
123
HamidN.Alsadi
Data ProcessingSection
Ministry of Oil
Baghdad
Iraq
ISSN 2509-372X ISSN 2509-3738 (electronic)
Advances in Oil andGasExploration & Production
ISBN978-3-319-40435-6 ISBN978-3-319-40436-3 (eBook)
DOI 10.1007/978-3-319-40436-3
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Preface
Thefavorablereceptionofthefirsteditionofthisbook(seismicExploration,
publishedbyBirkhauserVerlagin1980)stimulatedmybeliefintheneedof
an updated book that includes the advances in the techniques which have
taken place during the past three decades. In preparing the present updated
volume, I have taken into consideration the remarks and suggestions of the
users of the 1980 edition from both of the academic and industrial work
domains.
Since 1980, when the first edition of this book was published, great
developmentsintheseismicexplorationtechnologyhavetakenplace.These
developments have occurred in all of the three exploration phases: acquisi-
tion,processing,andinterpretationtechniques.Themostprominentadvances
which have taken place in these years are the widespread implementations
of the 3D surveying, pre-stack migration, and growing interpretation tech-
niques in both structural and stratigraphic exploration. As it is familiar with
theexplorationgeophysicists,thissubject(seismicexploration)isfullydealt
withinmanyoriginalandauthenticinternationallyknowntextbooks.Inthis
publication,nonewsubjectsaddedtothosefoundintheotherstandardbooks
which are well known in the geophysical library. In fact, these and other
related scientific papers and research reports formed solid references for the
presentbook. Thereare, however, differences inthe designand presentation
approach.
In its design, the book is intended to be a comprehensive treatise of the
seismic exploration tool, addressing audiences in both of the academic and
industrial establishments. It is made up of 12 chapters covering the basic
aspects of the seismic reflection exploration subject, starting with the basic
theory,followedbytheapplieddataacquisitiontechnology,andendingwith
the processing and interpretation. In presenting the subject matter, emphasis
is made on the practical aspects of the subject, using clear and simplified
presentation, avoiding excessive descriptions and unnecessary lengthy
comments. Numerous illustration figures (>390 figures) have been used
throughoutthebooktoaidinclarifyingtheconceptsandproceduresinvolved
in any standard seismic exploration survey. In this way, the book can be
considered as a very useful introductory teaching manual for university
students taking seismic reflection exploration as part of a postgraduate
course.
v
vi Preface
The chapters of the book are sequenced in the order of the activities
normallyexecutedinastandardseismicexplorationsurvey:fieldacquisition,
processing,andinterpretation.Chapter 1isanintroductorychapterinwhich
a brief historical note and short review of the geophysical exploration
methodsaregiven.Thisisfollowedbyfourchapterscoveringthetheoretical
aspect of the subject including basic principles and definitions of seismic
waves, with a special chapter assigned for the seismic wave propagation
velocity. The propagation phenomena, reflection, diffraction, transmission,
and refraction, are dealt within Chaps. 4 and 5. The followingtwo chapters
aredevotedtothetwomaintoolsappliedinseismicexploration,namelythe
2D and 3D surveying techniques.
Duetoitsimportantroleinunderstandingoftheprocessingstepsappliedin
seismicdataprocessing,achapter(Chap.8)isassignedsolelyfortheseismic
signal. This chapter is structured on the theme of considering the seismic
reflection wavelet as a propagating signal in the same way as the electro-
magnetic signal is treated by the communication theory applied in electro-
magneticwavepropagation.Includingachapteronseismicsignals,preceding
the processing chapters, is a feature by which this book has deviated from
other conventional publications. Data processing is presented under two
headings: processing tools (Chap. 9) and the normally applied processing
sequence(Chap.10).Chapter11coverssomespecializedseismicexploration
tools sometimes used in support of the conventional seismic reflection and
refractionsurveying.ThebookisconcludedwithChap.12oninterpretation.
IwouldliketoexpressmygratitudetomywifeAsiraandmysons(Eng.
Majid, Ph.D., Eng. Muhannad, M.Sc., Thurayah, B.Sc., and Eng. Mahir,
B.Sc.),fortheircontinuoussupportandhelpthroughoutthepastthree years.
Myworkinthewriting ofthebookhasincurredanadditional burden tothe
family especially during the abnormally difficult times, which our country
has experienced in the past twelve years.
Baghdad, Iraq Hamid N. Alsadi
December 2015
Contents
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Historical Review . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 Elasticity and Seismic Waves (Båth 1979) . . . 1
1.1.2 Earthquake Seismology (Richter 1958). . . . . . 2
1.1.3 Exploration Seismology
(Telford et al. 1990) . . . . . . . . . . . . . . . . . . 2
1.1.4 Summary of Exploration Seismology History
(Sheriff and Geldart 1995) . . . . . . . . . . . . . . 3
1.2 The Geophysical Exploration Project. . . . . . . . . . . . . 3
1.3 Geophysical Exploration Methods. . . . . . . . . . . . . . . 4
1.3.1 The Seismic Method . . . . . . . . . . . . . . . . . . 4
1.3.2 The Gravity Method . . . . . . . . . . . . . . . . . . 4
1.3.3 The Magnetic Method . . . . . . . . . . . . . . . . . 6
1.3.4 The Electical Method. . . . . . . . . . . . . . . . . . 7
1.3.5 The Radioactivity Method . . . . . . . . . . . . . . 9
1.4 Oil Well Drilling. . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4.1 Drilling of the Exploration-Well . . . . . . . . . . 10
1.4.2 The Oil-Well Rotary Drilling . . . . . . . . . . . . 10
1.4.3 The Drill-Hole and Well Casing . . . . . . . . . . 11
1.5 Well Geophysical Logging. . . . . . . . . . . . . . . . . . . . 11
1.5.1 Electrical Logging. . . . . . . . . . . . . . . . . . . . 12
1.5.2 Radioactivity Logging . . . . . . . . . . . . . . . . . 14
1.5.3 Acoustic Logging . . . . . . . . . . . . . . . . . . . . 16
1.5.4 Log Interpretation . . . . . . . . . . . . . . . . . . . . 19
1.6 Latest Developments in Well Logging. . . . . . . . . . . . 19
1.6.1 Logging While Drilling Technique . . . . . . . . 20
1.6.2 Borehole Imaging Tools. . . . . . . . . . . . . . . . 20
1.7 Well Completion. . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2 Seismic Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.1 The Fundamental Conditions . . . . . . . . . . . . . . . . . . 23
2.2 Theory of Elasticity. . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2.1 Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2.2 Strain . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.2.3 Common Types of Strain. . . . . . . . . . . . . . . 26
2.2.4 The Volume-Changing Strain . . . . . . . . . . . . 27
2.2.5 The Shape-Changing Strain . . . . . . . . . . . . . 28
2.2.6 The Cubical Dilatation. . . . . . . . . . . . . . . . . 28
vii
viii Contents
2.2.7 Stress-Strain Relationship. . . . . . . . . . . . . . . 29
2.2.8 Hooke’s Law for Isotropic Media . . . . . . . . . 29
2.2.9 The Elastic Moduli . . . . . . . . . . . . . . . . . . . 30
2.2.10 The Elastic Moduli Interrelationships. . . . . . . 32
2.3 Wave Motion Equation . . . . . . . . . . . . . . . . . . . . . . 32
2.3.1 One-Dimensional Scalar Wave Equation . . . . 33
2.3.2 The Scalar and Vector 3D Wave
Equations. . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.3.3 Plane Waves. . . . . . . . . . . . . . . . . . . . . . . . 35
2.3.4 The P- and S-Waves . . . . . . . . . . . . . . . . . . 36
2.4 Classification of Common Elastic Waves. . . . . . . . . . 36
2.4.1 Body Waves. . . . . . . . . . . . . . . . . . . . . . . . 37
2.4.2 Surface Waves . . . . . . . . . . . . . . . . . . . . . . 38
2.4.3 Seismic Noise. . . . . . . . . . . . . . . . . . . . . . . 39
2.5 Propagation of Seismic Waves . . . . . . . . . . . . . . . . . 40
2.5.1 Elements of the Seismic Field. . . . . . . . . . . . 41
2.5.2 Concepts of Wave-Fronts and Rays. . . . . . . . 41
2.5.3 Huygens’ Principle . . . . . . . . . . . . . . . . . . . 42
2.5.4 The Concept of the Interface . . . . . . . . . . . . 42
2.5.5 Changes of Propagation Direction at
Interfaces. . . . . . . . . . . . . . . . . . . . . . . . . . 43
2.5.6 Wave Conversion at Interfaces . . . . . . . . . . . 44
2.5.7 Energy Partitioning and Zoeppritz
Equations. . . . . . . . . . . . . . . . . . . . . . . . . . 45
2.5.8 Amplitude Variation with Angle
of Incidence. . . . . . . . . . . . . . . . . . . . . . . . 46
2.6 Effect of the Medium on Wave Energy . . . . . . . . . . . 46
2.6.1 Geometrical Spreading. . . . . . . . . . . . . . . . . 47
2.6.2 Inelastic Attenuation . . . . . . . . . . . . . . . . . . 48
2.6.3 Seismic Wave Energy Measurement
and the DB Unit. . . . . . . . . . . . . . . . . . . . . 49
2.6.4 The Logarithmic Decrement. . . . . . . . . . . . . 49
2.6.5 Wave Dispersion. . . . . . . . . . . . . . . . . . . . . 49
3 The Seismic Velocity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.2 Factors Influencing Seismic Velocity. . . . . . . . . . . . . 53
3.2.1 Lithology Effect . . . . . . . . . . . . . . . . . . . . . 53
3.2.2 Elasticity and Density Effects. . . . . . . . . . . . 54
3.2.3 Porosity and Saturation Fluid Effects. . . . . . . 54
3.2.4 Depth and Geological Age Effects. . . . . . . . . 56
3.2.5 Overburden Pressure Effect . . . . . . . . . . . . . 56
3.2.6 Other Velocity-Affecting Factors. . . . . . . . . . 57
3.3 The Velocity Function. . . . . . . . . . . . . . . . . . . . . . . 58
3.4 Types of Velocity Functions. . . . . . . . . . . . . . . . . . . 59
3.4.1 Instantaneous Velocity. . . . . . . . . . . . . . . . . 59
3.4.2 Interval Velocity. . . . . . . . . . . . . . . . . . . . . 60
3.4.3 Average Velocity . . . . . . . . . . . . . . . . . . . . 60
3.4.4 Root Mean Square Velocity . . . . . . . . . . . . . 61
3.4.5 Stacking Velocity . . . . . . . . . . . . . . . . . . . . 62
Contents ix
3.4.6 The Apparent Velocity. . . . . . . . . . . . . . . . . 63
3.4.7 The Group and Phase Velocities. . . . . . . . . . 64
3.4.8 Representations of the Velocity Functions . . . 64
3.5 Velocity Determination Methods. . . . . . . . . . . . . . . . 64
3.5.1 The Well Velocity Survey . . . . . . . . . . . . . . 65
3.5.2 The Up-Hole Velocity Survey. . . . . . . . . . . . 66
3.5.3 Continuous Velocity Logging. . . . . . . . . . . . 66
3.5.4 (X2 − T2 Method). . . . . . . . . . . . . . . . . . . . 67
3.5.5 (T − ΔT) Method . . . . . . . . . . . . . . . . . . . . 67
3.5.6 Velocity Analysis Method . . . . . . . . . . . . . . 68
3.5.7 Seismic Velocity Inversion. . . . . . . . . . . . . . 69
3.6 Uses of the Seismic Velocity Data. . . . . . . . . . . . . . . 69
4 Seismic Wave Reflection and Diffraction . . . . . . . . . . . . . . 71
4.1 The Commonly-Recorded Seismic Events . . . . . . . . . 71
4.2 Wave Changes at Reflection Interface . . . . . . . . . . . . 71
4.2.1 Reflection Coefficient at Inclined
Incidence. . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.2.2 Reflection Coefficient at Normal Incidence. . . 73
4.2.3 Geometry of Reflection from Dipping
Reflectors. . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.2.4 Geometry of Reflection from Horizontal
Reflectors. . . . . . . . . . . . . . . . . . . . . . . . . . 75
4.2.5 Reflection from Multiple Reflectors. . . . . . . . 75
4.3 The NMO and DMO Concepts. . . . . . . . . . . . . . . . . 76
4.3.1 The Normal Move-Out (NMO) Concept. . . . . 76
4.3.2 The Dip Move-Out (DMO) Concept . . . . . . . 79
4.4 The CDP, CRP, and CMP Concepts . . . . . . . . . . . . . 79
4.4.1 CDP, CRP, and CMP in Case
of Horizontal Reflector . . . . . . . . . . . . . . . . 80
4.4.2 CDP, CRP, and CMP in Case of Dipping
Reflector . . . . . . . . . . . . . . . . . . . . . . . . . . 80
4.5 The Seismic Wave Diffraction . . . . . . . . . . . . . . . . . 81
4.5.1 The Point-Diffractor . . . . . . . . . . . . . . . . . . 82
4.5.2 Diffraction from Terminating Reflectors. . . . . 83
4.5.3 Diffraction Seismic Image . . . . . . . . . . . . . . 83
4.5.4 Diffraction Travel-Time Function . . . . . . . . . 84
4.5.5 The Diffraction Hyperbola . . . . . . . . . . . . . . 85
4.5.6 Distortion Effects of Diffraction . . . . . . . . . . 86
4.5.7 The Exploding-Reflector Model . . . . . . . . . . 86
5 Seismic Wave Transmission and Refraction. . . . . . . . . . . . 89
5.1 Seismic Wave Transmission. . . . . . . . . . . . . . . . . . . 89
5.1.1 Transmission Coefficient at Normal
Incidence. . . . . . . . . . . . . . . . . . . . . . . . . . 89
5.1.2 The Two-Way Transmission Coefficient. . . . . 90
5.1.3 Attenuation Due to Reflection
and Transmission . . . . . . . . . . . . . . . . . . . . 90
5.1.4 Role of Transmission in Seismic
Exploration. . . . . . . . . . . . . . . . . . . . . . . . . 91
