Identification of a Pressure Compartment Boundary with Seismic Reflection Data in the Alberta Basin, Alberta, Canada

D. T. Maucione and R. C. Surdam

Previous work has demonstrated that regional pressure boundaries can be determined from well log data. A similar determination can be made using seismic data alone. Successful identification of a pressure boundary by two-dimensional seismic reflection data has been achieved in the Western Canada Basin. Specifically, a nearly 36 mile long profile was constructed southeast of the Elmworth Field area. Three 1993-vintage, 120-fold, vibroseis-sourced seismic lines (including structural strike and dip coverage) were reprocessed to preserve true amplitudes. Detailed velocity functions were selected. Ten wells were tied to the seismic coverage by synthetic seismograms generated from sonic and density logs.

Examination of the seismic data indicates that the following conditions correspond to the top pressure compartment boundary: (1) a change in reflection amplitudes generated by rock interfaces above and below this boundary; (2) a change in the semblance coherency plot velocity variation between common depth point gathers from the normally pressured, water-saturated section and the abnormally-pressured, gas-saturated section; (3) a change in velocity gradient of the stacking velocities above and below the boundary; and (4) increased interval velocity variation below the boundary.

By integrating the geological and geophysical data, the top pressure compartment boundary can be refined and identified in terms of depth. This study indicates that the boundary is located in part of the Upper Cretaceous Kaskapau shale.

This research was supported by the Gas Research Institute, contract #5089-260-1894.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California