Seismic amplitude variation with offset (AVO) is a particularly leveraging technique in North Slope oil and gas exploration, where the reservoir presence and quality are the greatest risks.  However, the arctic environment also introduces unique data quality problems, which must be overcome before AVO can be measured quantitatively.  This talk focuses on a method which normalizes and corrects seismic time, phase and amplitude variation with offset.  These variations are caused by ice lakes, permafrost variations and other subsurface geology.   The method first applies an ensemble automatic gain control, which corrects the time-varying amplitudes of individual gathers as a whole, but preserves their AVO.  Raw AVO intercept and gradient traces are then computed and destretched to remove offset-dependent tuning.  The intercepts and gradients are cross-correlated to estimate the background reflectivity.  Corrections are then made to the gradients to force them to conform to an area-wide background standard.  Seismic events which deviate significantly from the background are, by definition, “anomalies,” and can be further classified according to their location in the intercept-gradient plane.  This classification helps to determine reservoir quality and fluid type.  Product indicators classify AVO anomalies in a phase-independent manner.  Results from producing fields will be shown.

Biography

After receiving the BSEE and MSEE degrees from the University of Wisconsin, Dr. Swan was employed by Sandia National Laboratories in Livermore, Ca., as a Technical Staff Member.  He later worked in the Information Systems Laboratory of Stanford University, and in 1981 was awarded a Ph.D. degree in electrical engineering from that institution. From 1982 to 1998 he served as a Senior Research Geophysicist with Atlantic Richfield Company in their Plano Texas research center.  He is currently a Senior Staff Geophysicist with ConocoPhillips Alaska, Inc., located in Anchorage.  His specialties include AVO interpretation and modeling, amplitude-preserving seismic processing, reservoir characterization, and seismic attribute calibration.  He is a member of the SEG, where he serves and an Associate Editor of Geophysics, the District 1 Council Representative, and as a member of the Online Governing Board.  He is also a member of the EAGE and the AAPG, which recently awarded him the A. I. Levorsen award.