Seismic Response and Well Logs in Elastic Earth
Daniel C. Huston
The Zoeppritz
equations
show that seismic reflectivity varies with local
incidence angle and, in practice, hydrocarbon saturated sediments often produce
an increase in amplitude with increasing source receiver offset. Comparison of a
suite of well logs in gas and oil sands to pre-stack and partial stack surface
seismic data illustrates this occurrence. The well was drilled in a Gulf
Coast-style clastic basin and the marine seismic data are good quality 1970s
vintage. The seismic data show clear changes in amplitude vs. offset (AVO) and
correlate with hydrocarbon saturation shown on the resistivity log. However, the
seismic data are poorly matched with the sonic log. An interpretation based on
zero-offset acoustic impedance is inadequate here, and an elastic earth model is
required to help explain the data. Nearby seismic line intersections help
constrain the accuracy of the final one-dimensional interpretation.
AAPG Search and Discovery Article #91024©1989 AAPG Pacific Section, May 10-12, 1989, Palm Springs, California.