Print this pageDetection of Hydrocarbons with Lithostratigraphy
HILTERMAN, FRED J., JOHN W. SHERWOOD, ROBERT SCHELLHORN, and BRAD BANKHEAD, and BRIAN DE VAULT
In many basins, the acoustic-impedance values of shales and gas-saturated
sands are approximately equal and thus hydrocarbons are difficult to detect with
conventional 
3-D
seismic data. Even AVO has had limited success because of the
questionable relationship of the AVO attributes to media properties.
In order to resolve these questions, a 3-D AVO study was conducted utilizing
well-logs, cores, and production data to help calibrate the seismic response to
the media properties. The subsequent AVO inversion yields two distinct
reflectivities, a normal-incidence and a Poisson. The estimation of the
Poisson-reflectivity section is stabilized by including CDP traces that have
offsets as great as twice the depth. This requires the inclusion of an isotropic
corrections
in the total processing flow.
The reflectivities are then related to chronostratigraphic and lithostratigraphic sections. The lithologic correlation results from petrophysical relationships of SP well-log curves to Poisson's ratio curves while the chronostratigraphic correlation relies on seismic-stratigraphy. The benefit of these two sections is that the lithostratigraphic section (Poisson reflectivity), contains only very clean wet sand and/or gas-saturated sand events while the normal incidence section is a high resolution structural image.