Differential compaction of Winnipegosis reefs: A seismic perspective

Abstract

Winnipegosis Formation reefs in southern Saskatchewan are typically encased in the thick, apparently incompressible salts of the Prairie Evaporite. These reefs are characterized by raised rims and reverse drape along the top of the salt. Both features, clearly visible on seismic data, are primarily due to postdepositional compaction. The rims developed principally as a result of differential compaction within the different reef environments; the structural low at the Prairie Evaporite level is attributed to differential compaction between the reef and the encasing salt. If these salts are effectively incompressible, the rim and lagoonal facies are estimated to have been compacted by at least 30 and 44 percent, respectively. This paper illustrates the usefulness of seismic data to separate postdepositional compaction features from primary features to determine the primary morphology of a reef better and to determine the relative amounts of postdepositional compaction within the different reef environments. The degree to which the reef rim and interior areas were compacted can be estimated based on interpretation of the example seismic line. The methods and results of this paper allow for better definition of prime target areas for potential hydrocarbon reservoirs within the reef proper.