Inventors:
Herbert W. Swan - Richardson TX
Kenneth O. McDowell - Midland TX
James A. Specht - Plano TX
Assignee:
Atlantic Richfield Company - Los Angeles CA
International Classification:
G01V 136
G01V 134
Abstract:
A method and apparatus for analyzing amplitude-versus-offset (AVO) seismic data to distinguish sand formations, such as Morrow sands, from limestones and other similar intervals, is disclosed. For each of the traces in the survey, AVO intercept and AVO slope traces are generated, preferably after normalization of the amplitudes of the traces to account for geophone coupling variations. After normalization and conventional processing and corrections, spatial summation may be performed to further improve the traces. AVO trend lines are then generated, preferably on a weighted window basis, to generate localized trend lines against which the intercept and slope values of individual depth points may be compared. This comparison allows the plotting of AVO intercept versus AVO slope deviation from the trend line, from which sand formation interfaces may be identified by their presence in certain quadrants of the intercept-slope deviation cross-plot.