Advances 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 The book series Advances in Oil and Gas Exploration & Production pub- lishes scientific monographs on a broad range of topics concerning geo- physicalandgeologicalresearchonconventionalandunconventionaloiland gas systems, and approaching those topics from both an exploration and a production standpoint. The series is intended to form a diverse library of reference works by describing the current state of research on selected themes,suchascertaintechniquesusedinthepetroleumgeosciencebusiness orregionalaspects.Allbooksin theseries arewrittenand edited byleading experts actively engaged in the respective field. The Advances in Oil and Gas Exploration & Production series includes both single andmulti-authored books, aswell aseditedvolumes.TheSeries Editor, Dr. Rudy Swennen (KU Leuven, Belgium), is currently accepting proposals and a proposal form can be obtained from our representative at Springer, Dr. Alexis Vizcaino ([email protected]). More information about this series at http://www.springer.com/series/15228 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 LibraryofCongressControlNumber:2016942906 ©SpringerInternationalPublishingSwitzerland2017 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeor part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,recitation,broadcasting,reproductiononmicrofilmsorinanyotherphysicalway, andtransmissionorinformationstorageandretrieval,electronicadaptation,computersoftware, orbysimilarordissimilarmethodologynowknownorhereafterdeveloped. Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthis publication does not imply, even in the absence of a specific statement, that such names are exemptfromtherelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. Thepublisher,theauthorsandtheeditorsaresafetoassumethattheadviceandinformationin thisbookarebelievedtobetrueandaccurateatthedateofpublication.Neitherthepublishernor the authors or the editors give a warranty, express or implied, with respect to the material containedhereinorforanyerrorsoromissionsthatmayhavebeenmade. Printedonacid-freepaper ThisSpringerimprintispublishedbySpringerNature TheregisteredcompanyisSpringerInternationalPublishingAGSwitzerland 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