Sublette, Victoria¹ 
(1) Weinman GeoScience, Dallas, TX

ABSTRACT: Reducing the Assumptions - AVO Processing Tools from BP's AVO Workbench

A myriad of assumptions underlie any AVO analysis project. Two key points among these are a) that the gathers are flat enough for accurate attribute extraction and b) that calibrations of seismic response made with the well control accurately predict the behavior of the seismic some distance away at the prospect. 
But how flat is flat enough? And how does one measure and stabilize the spatial and temporal variations of the background sand-shale trends? 
First, we will quantify the impact of velocity error on AVO attribute calculation and present a practical application of the high resolution velocity technique introduced by Swan using software licensed through agreement with BP. 
The second part of the talk focuses on an analysis of the variations in the background trends as seen in a suite of crossplot analyses on a data volume that has had current industry best practice amplitude preserving processing applied. These crossplots demonstrate that the assumption of a background trend lying neatly at a 45 degree angle in the center of a well-defined ellipse almost never holds true – even in good data. A technique is then demonstrated for normalizing variations in the wet sand/shale trend using a statistical approach developed at ARCO and licensed through BP.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.