Print this pageMap View Subsalt AVO Modeling
LINDSAY, RICHARD O., DAVID R. MUERDTER, CHARLES M. SKIDMORE, AND DAVIS W. RATCLIFF
3-D
PreStack Depth Migration (3-D PreSDM) has demonstrably
opened the Gulf of Mexico Subsalt Trend by producing clear and well
defined images of the pre-salt geologic section. Amplitude and AVO
anomalies have subsequently mapped and by drilling, proven to be associated
with hydrocarbons.Yet to date, these associations are qualitative
at best.
Insight into the understanding of subsalt amplitude and AVO anomalies
is gained by the combination of 3-D raytracing, 3-D pore pressure
prediction and map-domain AVO modeling. 3-D
raytracing through the 3-
D PreSDM velocity volume into the pre-salt section reveals a richness of
incidence angles on subsalt horizons.The magnitude and richness of distribution
of these angles was not anticipated from simple salt layer models.
From this insight alone one must anticipate AVO anomalies in the
subsalt section.
Collected from raytracing are volumes of incidence angles at perspective subsalt horizons. Extracted at prospective horizons, these angles are combined with spatially varying shale cap-rock and reservoir rock properties (caused by variations i pore pressure) to create seismic amplitude and AVO model maps. Multiple solutions are created while varying the reservoir pore fluids. Revealed is insight into decoupling the raypath distortion and pore pressure effects from reservoir pore fluid effects.