The old way of seismic data analysis involves processing, imaging and interpretation – all in the time domain, conducted sequentially. This sequence is then followed by time-to-depth conversion.
The Conversion Way
|Time Domain||Time Domain||Time Domain|
The new paradigm for seismic data analysis involves processing in time, followed by inversion for earth modeling and imaging in the depth domain, conducted concurrently.
The Inversion Way
|Time Domain||Depth Domain||Depth Domain|
Simply put, the old way involves interpretation in time followed by conversion to depth. The new paradigm involves inversion for earth modeling in depth. With the new paradigm, interpretation is implicit to earth modeling in depth – by the time you've completed analysis of your data, you also have done your interpretation.
Note that processing refines the data you acquire, whereas inversion creates knowledge – an earth model in depth and an earth image in depth. Also note that a measure of uncertainty about the information is as important as the information itself – you have it in depth, not in time.
To conduct seismic data analysis with the new paradigm, you need to integrate systems for processing, interpretation and inversion. Results of conventional processing – stacking velocities, CMP gathers and CMP-stacked data, and results of time-domain interpretation - time structure maps, are downloaded to an inversion system for earth modeling and imaging in depth.
Estimation of structural models is largely based on traveltime inversion methods, and that of stratigraphic models is based on amplitude inversion methods. When combined, the structural and stratigraphic models constitute seismic representation of an earth model in depth. The structural model is used to derive an earth image in depth. Finally, the seismic representation of an earth model in depth needs to be transcribed into petrophysical representation – a reservoir model. Note that inversion is the agent of integration - it moves you from time to depth domain.
Estimation of an earth model can be done in two different manners – structure-dependent and structure-independent. I shall present case studies for earth modeling and imaging in depth using appropriate combinations of inversion methods.
About the Author(s)
Dr. Ozdogan Yilmaz earned his B.S. in Geophysics (first honors) from the University of Missouri-Rolla in 1970 and M.S. in Geophysics from Stanford University in 1972. His master's research was primarily in rock physics and earthquake seismology. He was employed by Turkish Petroleum Corporation between 1973 and 1978 then returned to Stanford, where he did research work in exploration seismology as a member of the Stanford Exploration Project Group and received his Ph.D. in geophysics in 1979. He then joined Western Geophysical in Houston and moved to the London office in 1983. He then joined Schlumberger as Director of Data Analysis Product Development Group, responsible for processing, inversion and interpretation software technology, then Founded WorldWide Inversion Services Group at Geco-Prakla and was Director of the group until he joined Paradigm Geophysical on January 1, 1997 as Managing Director of the EAME region. He has 24 years of experience in the oil and gas industry, which includes research and geophysical software development, seismic data acquisition and processing, inversion and interpretation, teaching in the industry, and gravity and magnetic data processing and interpretation.
Aside from publications on all aspects of seismic data analysis, he wrote a book entitled Seismic Data Processing, which was published by the Society of Exploration Geophysicists in 1987 and became the all-time best seller in the geophysical literature. The book is used in academia as the standard textbook and as the main reference on the subject in the seismic industry. Now, he is' working on the second edition and preparing a second book on seismic inversion.
Oz is a member of SEG and EAGE, and was Vice-President of SEG for the 1993-94 term, and the SEG 1996 Spring Distinguished Lecturer. He has taught a course on 3-D Seismic Exploration as part of the Continuing Education Program of SEG and served as an Associate Editor of Geophysical Prospecting of EAGE. He organized the 1994 SEG/EAGE Summer Workshop on Earth Modeling and Imaging in Depth, and the Istanbul 1997 SEG International Conference and Exposition.
For his contributions to the science of geophysical exploration, Oz was honored by the Society of Exploration Geophysicists in 1991 with the Virgil Kauffman Gold Medal Award, and by the European Association of Geoscientists and Engineers (then known as the European Association of Exploration Geophysicists) in 1992 with the Conrad Schlumberger Award. He was also honored with Special Commendation Award by the Technical University of Istanbul in 1992 and for his contributions to the geophysical profession in a global manner, his biography has been included in Marqui's Who's Who in the World, 1997 edition.