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SWLGS Luncheon Topics

Updated Oct. 3, 2005

October 2005

The Impact of Pre-Stack Data Phase on the AVO Interpretation Workflow- A Case Study
Rocky Roden, John Castagna, and Gary Jones


Abstract Summary
In the conventional approach of interpreting stacked seismic data, it is quite common to rotate the phase of the data to match synthetic correlations and/or to get isolated reflections in the data as close as possible to zero phase. Understanding the phase of the data is extremely important in the interpretation workflow and has significant implications for the final interpretation and drilling of wells. This functionality is available on most interpretation systems today. What is not routine in the normal interpretation process is to phase rotate gathers to determine how this affects the final stacked volume, the analysis of the pre-stack data, and ultimately the final interpretation of the prospect. Depending on the phase of gathers, the generation of various AVO attributes for crossplotting can produce varied results, which may adversely obscure or highlight significant trends in the data. From a 3D data set in the shallow waters offshore Louisiana, an AVO interpretation of pre-stack gathers and AVO crossplots was found to be quite beneficial in understanding the phase of the data and its impact on defining acoustic reservoir thickness.

Biographical Sketch
Rocky Roden has been successful in managing and administering programs and technical staffs in exploration and development, domestically and worldwide, for the past 30 years. He is a proven oil finder with extensive knowledge of modern geoscience technical approaches (past Chairman-The Leading Edge Editorial Board). As Chief Geophysicist for Repsol-YPF, his role comprised advising corporate officers, geoscientists, and managers on interpretation, strategy and technical analysis for exploration and development in offices in U.S., Argentina, Spain, Egypt, Bolivia, Ecuador, Peru, Brazil, Venezuela, Malaysia, and Indonesia. He was directly involved in the design and organization of the risk analysis program at YPF-Maxus. He has been involved in the technical and economic evaluation of Gulf of Mexico lease sales, farmouts worldwide, and bid rounds in Ecuador, Venezuela, China, Hungary, Colombia, and Trinidad. Previous work experience includes exploration and development at Maxus Energy, Pogo Producing, Decca Survey, and Texaco. Rocky presently consults with Seismic Micro-Technology as New Products Design Consultant, is a principle in the Rose and Associates DHI Risk Analysis Consortium, and consults with several oil companies on technical and reserve evaluation issues (BS, Oceanographic Technology-Geology, Lamar University; MS, Geological and Geophysical Oceanography, Texas A&M University).

Gary L. Jones is an exploration geophysicist with experience in acquisition, processing and interpretation of Seismic. He started with several seismic contractors doing acquisition and processing before moving to a Union Pacific Resource where he did exploration geophysics. His recent focus has been the development of geophysical interpretation software, initially with Landmark Graphics, and is presently the product manager of AVOPAK at Seismic Micro Technology. His interests include sequence stratigraphy, thin sand analysis, and the visualization and interpretation of 3D seismic data. (BS Geophysical Engineering, Colorado School of Mines 77)