- Email: [email protected]
Practical seismic interpretation
Geophysical Signal Processing E. A Robinson, T. S. Durrani and L. G. Peardon Prentice Hall International, 1985; ISBN 13-352667-4; £49.95 The authors's purpose in writing the book is stated in the Preface to be 'to fill a gap in the literature of applied geophysical signal processing between the many introductory texts on the one hand and the research journals on the other." By geophysical signals, they mean seismic reflection data exclusively. In this reviewer's opinion, the book is successful in providing a bridge, but only for a restricted range of topics which have been so well-trodden that the existence of the gap for them is open to doubt, The book is exceptionally well produced having a wealth of diagrams and explanatory text while not dodging the mathematical expression and justification of the techniques described. Excellent sets of exercises are provided for the student of those chapters written by E. A. Robinson. The processes covered have been, by and large, the workhorses of conventional seismic data processing for the better part of a quarter of a century. The section by E. A. Robinson is devoted to NMO correction and stacking, predictive deconvolution and time migration: that by T. S. Durrani covers 1-D synthetic seismogram generation, Wiener filtering and wave shaping algorithms, and the part by L. G. Peardon deals with F - K analysis and filtering. Individually the authors are to be congratulated on clear expositions, but there is evidence of lack of collusion between them. F - K migration is explained twice. The chapters follow no logical order. There is some cross referencing but it cannot be relied on. The same concepts are described with different symbolism in different places. Durrani calls z the delay operator (p 314) but uses it (consistenty with Robinson) as the advanced operator. Other
confusions could lurk for the unwary. Perhaps most serious however are the omissions. I could find no hint of the vital fact that stacking velocity is a well-defined function of reflector dip. Nor could I locate any mention of the Hilbert transform, a fundamental item of equipment for many important frequency domain operations including minimum phase evaluation, phasor analysis and the p-~ or Radon transform, none of which are dealt with. Depth migration is properly put forward as the only correct way of imaging the sub-surface, yet no hint is given as to how it is done, though it has been a commercially available process for at least nine years. Prestack migration and other pre-stack processes such as Dip Moveout (alias Partial Prestack Migration, or Offset Continuation) which are coming into common use are not referred to. Synthetic VSPs are described but nowhere is the processing of VSPs touched on. The whole vast arena of 3-D data processing is ignored. All of these matters are susceptible to simple exposition and I feel some of them could better have replaced the over-full treatment of, for instance, the WKB method (24 pages long) without unduly expanding the book. If you don't already have books which cover 'conventional' seismic data processing theory, then this is a good one. As a gap filler, however, I feel it comes 5-10 years too late. The gap yawns eleswhere now, and we are still waiting for someone to fill it.
J . W . 3. Hosken
Practical Seismic Interpretation M. E. Badley D. Reidel, 1985; ISBN: 90-277-2100-9; Dfl 230,00/£63.75 I write this review at a time when seismic interpreters just starting out in the oil industry are looking over their shoulders at the price of oil and thinking of their careers. So has Badley's book come at an inopportune moment? I sincerely hope not; because here is a really useful practical guide to the interpretation of commercial seismic reflection profiles. [ cannot summarize the aims (and achievements) of the book better than the author does in the Preface: 'This book is about the practical aspects of reflection seismic interpretations, written by a working explorationist or explorationists. It is neither mathematical nor theoretical and does not claim to give a comprehensive treatment of the seismic-reflection method. The more geophysical topics, such as acquisition, processing, modelling, and so on, are not dealt with in any detail. The book does deal, however, with many of the everyday practicalities and problems facing the working interpreter; and, as such, has a geological bias. The book is aimed especially at those new to interpretation, who, when confronted with a pile of fresh seismic sections, wonder where to start the interpretation, what to pick, how to recognise multiples and so forth', The book is divided into two halves, but these are not a geophysical half and a geological half as might be expected.
The first half covers the areas of knowlege that ever interpreter needs before starting on an interpretation, including both geophysical and geological material. The second half deals with practicalities and techniques of the interpretation itself. The text is profusely illustrated, although the reproduction of seismic sections onto the rather grainy paper leaves a little to be desired where detail is important. A lot of the technical diagrams are familiar, having been culled from existing texts; but herein lies a strength of the book in that there is what I consider to be an excellent reference list. The latter contains carefully selected, classic and up-to-date (to end-1983) references constituting a basic and essential collection for seismic interpretation. Another element to the text is a set of twenty relatively short questions with answers that will prove useful to teachers who are pressed for time to carry out a full seismic survey interpretation exercise. The text contains all the well-aired aspects of interpretation, such as pitfalls, seismic stratigraphy, velocity analysis and its uses etc. What it has in addition, however, that makes the book just that little bit more useful than others are the really practical tips. In this respect I especially liked the account of the seismic section label in the chapter on Data Preparation and Preliminary Studies. This is the sort of thing
338 Marine and Petroleum Geology, 1986, Vol 3, November
Book Reviews that is rarely found in other texts and yet provides vital informaion to the interpreter on the probable limitations of the data. I have two negative comments. Firstly, there is disappointing, indeed only passing, treatment of 3D data acquisition and interpretation. In a book that is up-to-date enough to recognize that explorationists rather than pure geologists or geophysicists are the order of the day in exploration teams, it is surprising that 3D is not given a greater mention. Perhaps the author feels that the interpreter who sits at a 3D work station has moved a bit too far away from the basic geological and geophysical skills that brought him into the exploration team and need not be considered here. Secondly having recently reviewed another book on seismic interpretation, in which case studies of specific oil or gas fields gave a clear indication of how different one interpretation exercise can be from another, I feel it is a pity that case studies are missing from this book.
It is clear that this book is aimed at those at the training stage in seismic interpretation, but it is amply acknowledged by the author that interpretation skills are not acquired simply by reading the book. The book has evolved from a manual to accompany a course in seismic interpretation and needs to be read in conjunction with practical tuition with seismic sections. It is ideally suited to courses at MSc level in universities or to introductory courses within the commercial world. It may also be useful to final year under-graduates in geology and geophysics and to PhD students who may be more or less finding their own way. The material in the book has had many opportunities to be tried and tested and is now honed into a well balanced, well written text that pretty well achieves what it sets out to do.
R. A Scrutton
Theory and Evaluation of Formation Pressures: A Pressure Detection Reference Handbook EXLOG Series of Petroleum Geology and Engineering Handbooks D. Reidel Publishing Co/International Human Resources Development Corporation ISBN-0-88746-052-6 Sediments compact due to overburden pressure and all rocks at depth are subject to this geoslatic pressure. The measuremerit of pressure gradients with depth and in particular the detection off overpressure is of fundamental importance to e.g. hydrocarbon migration, formation evaluation, reservior development and drilling. Although the causes of changes in formation pressures are well known to geologists, the detail of pressure measurement and its applications to drilling, fracturing etc. are probably best understood by petroleum and drilling engineers. Typically, the necessary pressure measurements are provided by service contractors. The authors of this book, Exploration Logging, is a well known contractor providing a wide range of specialist services to oil exploration including well logging and formation pressures evaluation. This book is one of a series that fully describes the theory and practice of E X L O G techniques and is probably an edited version of a manual provided to E X L O G staff, The stated purpose of the book is to educate the prospecrive 'Pressure Evaluation Geologist' as well as to provide a basic reference text designed to foster 'constructive thought and continued development of the field geologist'. The first two chapters of the book provide brief introduction to the responsibilities of the 'Pressure Evaluation
Geologist' and a 30 page discussion of the geological processes causing overpressures. The discussion is simple and straightforward although many geologist would take a more sophisticated view. This section of the book provides a useful introduction to engineers although there is no reference later than 1978. The larger part of the book (Chapters 3 to 5) is dedicated to pore pressure evaluation techniques, lost circulation, hydraulic fracturing and kicks. These chapters each provide an introduction and a simple but complete qualitative and quantitative discussion of the theory with exemplary calculations with warning of pitfalls in interpretation and measurement; safety aspects are also included in the test. These chapters are probably the most valuable part of the book and will provide a useful reference text. The main value of the book is a manual describing formation pressure measurements, calculations and in turn application to a variety of problems. As such, the book will be a useful reference for geologists drilling and reservoir engineers. D . G . Roberts
Formation Evaluation Exlog. Ed. Alun Whittaker D. Reidel, 1985; ISBN 90-277-1978-0; Dfl 115,00/£31.95 This 'handbook' is written by staff of Exploration Logging and edited by Alun Whittaker. It is one in a series of six publications covering a variety of petroleum engineering and geological subjects directly related to wellsite operations, The series is part of the training scheme devised by Exlog for their staff from their initial recruitment to more advanced levels. The editor in fact states that the book is designed for the graduate geologist joining the oil industry. Generally, the contents are pitched at about the right level for the new graduate, however some topics are treated too basically to be anything other than reminders, Chapter One is an introduction and throws the reader straight into a discussion of advanced fluid-flow mechanics as
related to the recovery of samples. Although very interesting and important, it can be a little off-putting this early into a book and might be better added as an appendix. The chapter continues with details on cuttings sampling and preparation, important for both the mud-logger and less experienced wellsite geologist. Much of this information is in fact dealt with in other volumes in the series. The remainder of the book is a detailed classification of rock samples in relation to their occurrence, identification, description and significance as drill cuttings at the wellsite. It is divided into four further chapters on Detrital, Carbonate, Chemical and Igneous/Metamorphic rocks. The understanding of basic classifications should be known by any graduate
Marine and Petroleum Geology, 1986, Vol 3, November
339
confusions could lurk for the unwary. Perhaps most serious however are the omissions. I could find no hint of the vital fact that stacking velocity is a well-defined function of reflector dip. Nor could I locate any mention of the Hilbert transform, a fundamental item of equipment for many important frequency domain operations including minimum phase evaluation, phasor analysis and the p-~ or Radon transform, none of which are dealt with. Depth migration is properly put forward as the only correct way of imaging the sub-surface, yet no hint is given as to how it is done, though it has been a commercially available process for at least nine years. Prestack migration and other pre-stack processes such as Dip Moveout (alias Partial Prestack Migration, or Offset Continuation) which are coming into common use are not referred to. Synthetic VSPs are described but nowhere is the processing of VSPs touched on. The whole vast arena of 3-D data processing is ignored. All of these matters are susceptible to simple exposition and I feel some of them could better have replaced the over-full treatment of, for instance, the WKB method (24 pages long) without unduly expanding the book. If you don't already have books which cover 'conventional' seismic data processing theory, then this is a good one. As a gap filler, however, I feel it comes 5-10 years too late. The gap yawns eleswhere now, and we are still waiting for someone to fill it.
J . W . 3. Hosken
Practical Seismic Interpretation M. E. Badley D. Reidel, 1985; ISBN: 90-277-2100-9; Dfl 230,00/£63.75 I write this review at a time when seismic interpreters just starting out in the oil industry are looking over their shoulders at the price of oil and thinking of their careers. So has Badley's book come at an inopportune moment? I sincerely hope not; because here is a really useful practical guide to the interpretation of commercial seismic reflection profiles. [ cannot summarize the aims (and achievements) of the book better than the author does in the Preface: 'This book is about the practical aspects of reflection seismic interpretations, written by a working explorationist or explorationists. It is neither mathematical nor theoretical and does not claim to give a comprehensive treatment of the seismic-reflection method. The more geophysical topics, such as acquisition, processing, modelling, and so on, are not dealt with in any detail. The book does deal, however, with many of the everyday practicalities and problems facing the working interpreter; and, as such, has a geological bias. The book is aimed especially at those new to interpretation, who, when confronted with a pile of fresh seismic sections, wonder where to start the interpretation, what to pick, how to recognise multiples and so forth', The book is divided into two halves, but these are not a geophysical half and a geological half as might be expected.
The first half covers the areas of knowlege that ever interpreter needs before starting on an interpretation, including both geophysical and geological material. The second half deals with practicalities and techniques of the interpretation itself. The text is profusely illustrated, although the reproduction of seismic sections onto the rather grainy paper leaves a little to be desired where detail is important. A lot of the technical diagrams are familiar, having been culled from existing texts; but herein lies a strength of the book in that there is what I consider to be an excellent reference list. The latter contains carefully selected, classic and up-to-date (to end-1983) references constituting a basic and essential collection for seismic interpretation. Another element to the text is a set of twenty relatively short questions with answers that will prove useful to teachers who are pressed for time to carry out a full seismic survey interpretation exercise. The text contains all the well-aired aspects of interpretation, such as pitfalls, seismic stratigraphy, velocity analysis and its uses etc. What it has in addition, however, that makes the book just that little bit more useful than others are the really practical tips. In this respect I especially liked the account of the seismic section label in the chapter on Data Preparation and Preliminary Studies. This is the sort of thing
338 Marine and Petroleum Geology, 1986, Vol 3, November
Book Reviews that is rarely found in other texts and yet provides vital informaion to the interpreter on the probable limitations of the data. I have two negative comments. Firstly, there is disappointing, indeed only passing, treatment of 3D data acquisition and interpretation. In a book that is up-to-date enough to recognize that explorationists rather than pure geologists or geophysicists are the order of the day in exploration teams, it is surprising that 3D is not given a greater mention. Perhaps the author feels that the interpreter who sits at a 3D work station has moved a bit too far away from the basic geological and geophysical skills that brought him into the exploration team and need not be considered here. Secondly having recently reviewed another book on seismic interpretation, in which case studies of specific oil or gas fields gave a clear indication of how different one interpretation exercise can be from another, I feel it is a pity that case studies are missing from this book.
It is clear that this book is aimed at those at the training stage in seismic interpretation, but it is amply acknowledged by the author that interpretation skills are not acquired simply by reading the book. The book has evolved from a manual to accompany a course in seismic interpretation and needs to be read in conjunction with practical tuition with seismic sections. It is ideally suited to courses at MSc level in universities or to introductory courses within the commercial world. It may also be useful to final year under-graduates in geology and geophysics and to PhD students who may be more or less finding their own way. The material in the book has had many opportunities to be tried and tested and is now honed into a well balanced, well written text that pretty well achieves what it sets out to do.
R. A Scrutton
Theory and Evaluation of Formation Pressures: A Pressure Detection Reference Handbook EXLOG Series of Petroleum Geology and Engineering Handbooks D. Reidel Publishing Co/International Human Resources Development Corporation ISBN-0-88746-052-6 Sediments compact due to overburden pressure and all rocks at depth are subject to this geoslatic pressure. The measuremerit of pressure gradients with depth and in particular the detection off overpressure is of fundamental importance to e.g. hydrocarbon migration, formation evaluation, reservior development and drilling. Although the causes of changes in formation pressures are well known to geologists, the detail of pressure measurement and its applications to drilling, fracturing etc. are probably best understood by petroleum and drilling engineers. Typically, the necessary pressure measurements are provided by service contractors. The authors of this book, Exploration Logging, is a well known contractor providing a wide range of specialist services to oil exploration including well logging and formation pressures evaluation. This book is one of a series that fully describes the theory and practice of E X L O G techniques and is probably an edited version of a manual provided to E X L O G staff, The stated purpose of the book is to educate the prospecrive 'Pressure Evaluation Geologist' as well as to provide a basic reference text designed to foster 'constructive thought and continued development of the field geologist'. The first two chapters of the book provide brief introduction to the responsibilities of the 'Pressure Evaluation
Geologist' and a 30 page discussion of the geological processes causing overpressures. The discussion is simple and straightforward although many geologist would take a more sophisticated view. This section of the book provides a useful introduction to engineers although there is no reference later than 1978. The larger part of the book (Chapters 3 to 5) is dedicated to pore pressure evaluation techniques, lost circulation, hydraulic fracturing and kicks. These chapters each provide an introduction and a simple but complete qualitative and quantitative discussion of the theory with exemplary calculations with warning of pitfalls in interpretation and measurement; safety aspects are also included in the test. These chapters are probably the most valuable part of the book and will provide a useful reference text. The main value of the book is a manual describing formation pressure measurements, calculations and in turn application to a variety of problems. As such, the book will be a useful reference for geologists drilling and reservoir engineers. D . G . Roberts
Formation Evaluation Exlog. Ed. Alun Whittaker D. Reidel, 1985; ISBN 90-277-1978-0; Dfl 115,00/£31.95 This 'handbook' is written by staff of Exploration Logging and edited by Alun Whittaker. It is one in a series of six publications covering a variety of petroleum engineering and geological subjects directly related to wellsite operations, The series is part of the training scheme devised by Exlog for their staff from their initial recruitment to more advanced levels. The editor in fact states that the book is designed for the graduate geologist joining the oil industry. Generally, the contents are pitched at about the right level for the new graduate, however some topics are treated too basically to be anything other than reminders, Chapter One is an introduction and throws the reader straight into a discussion of advanced fluid-flow mechanics as
related to the recovery of samples. Although very interesting and important, it can be a little off-putting this early into a book and might be better added as an appendix. The chapter continues with details on cuttings sampling and preparation, important for both the mud-logger and less experienced wellsite geologist. Much of this information is in fact dealt with in other volumes in the series. The remainder of the book is a detailed classification of rock samples in relation to their occurrence, identification, description and significance as drill cuttings at the wellsite. It is divided into four further chapters on Detrital, Carbonate, Chemical and Igneous/Metamorphic rocks. The understanding of basic classifications should be known by any graduate
Marine and Petroleum Geology, 1986, Vol 3, November
339