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The upper Mission Canyon Formation along the east flank of the Williston basin represents several upward-shoaling cycles within an overall regressive marine sequence. Individual cycles grade from offshore shelf carbonates eastward into restricted marginal marine evaporites. This depositional pattern and subsequent diagenesis have produced numerous prolific hydrocarbon traps.
The relationship of hydrocarbon occurrence to facies distribution, paleostructure, and porosity development is discernable by constructing a variety of isopach, lithofacies, and porosity maps. Two areas in the vicinity of Chola-Mackobee Coulee and Glenburn fields permit detailed analysis of the Bluell, Sherwood, Mohall, and Glenburn cycles.
Anhydrite distribution and thickness variation within individual Mission Canyon cycles most closely correspond to the pattern of hydrocarbon occurrence. Other major factors governing such occurrence include the lateral distribution and succession of carbonate bank, dolomite, anhydrite, and siliciclastic lithofacies.
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