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MARK, SANDRA, and ROGER M. SLATT, Petroleum Technology Transfer Council, Colorado School of Mines, Golden, CO; and DAVID C. RAMPTON, Shell Oil Company, The Hague, Netherlands

Abstract: Characterizing a Morrow Sandstone Reservoir Through Stratigraphic Interpretation of 3-D Seismic Data, Sorrento Field, Colorado

Sorrento Field, southeastern Colorado, contains an estimated 21 million barrels of original oil in place in the Pennsylvanian Morrow sandstone. The reservoir consists of a complex of stacked channel sequences within an incised valley. Interpretation of 3D compressional seismic data has outlined the configuration of the incised valley and provided essential information about the characteristics of the rocks that fill it. This seismic interpretation provides stratigraphic details on the compartmentalization of the four flow units which explain the multiple fluid contacts and variable performance of wells in the field.

The petroleum industry has been challenged to characterize Morrow reservoirs because the sandstone reservoir is encased in marine mudstone; normal compressional seismic data are not capable of imaging reservoir rock because the acoustic impedance is not sufficient to distinguish the two lithologies. Rather, seismic modeling shows that the compressional seismic character of the Morrow interval is primarily due to high velocity/high density non-reservoir rocks. The distribution of these non-reservoir rocks is critical in delineating the reservoir because the channel sandstone is bordered by reflective rocks such as floodplain deposits or high density facies which lie outside of the valley wall. Non-reservoir rocks which are barriers to flow within the reservoir, such as carbonate-cemented zones, define the compartmentalization.

AAPG Search and Discovery Article #90921©1999 AAPG Mid-Continent Section Meeting, Wichita, Kansas