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