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The AAPG/Datapages Combined Publications Database
Williston Basin Symposium
Abstract
NDGS/SKGS-AAPG
Fourth International Williston Basin Symposium, October 5,
MISSION CANYON AND DUPEROW RESERVOIRS OF THE BILLINGS NOSE, BILLINGS COUNTY, NORTH DAKOTA
ABSTRACT
The Billings Nose comprises a number of fields (Big Stick, Four Eyes, TR, Tree Top, and Whiskey Joe) which have coalesced into one large producing area situated on a northward plunging anticline. The Mission Canyon and Duperow reservoirs are the most prolific in the area, having combined cumulative production of over 25 million barrels of oil (as of January 1982), and present an interesting challenge to the explorationist.
The structural nose is a result of regional basement tectonic activity and can be seen on maps of deeper horizons, broad to the south and narrower to the north. Small intricate structures mapped at Mission Canyon level (using ten foot contours) may be indicative of multi-stage solution of Devonian salt. This complex pattern of "bumps" and "holes" superimposed on the overall nose is too erratic to attribute solely to basement tectonics.
Anhydrite and associated tight limestone near the top of the Mission Canyon (Nesson interval) provide the seal for the stratigraphic trap for hydrocarbons present in the underlying porous dolomite. The tidal flat depositional environment in which the original sediments accumulated is complicated by numerous tidal channels and supratidal ponds. Identification of thin porous units and/or small, subtle structures within the Nose is necessary for locating petroleum accumulations. The overall trend of steps or pinchouts of porous units can be determined by mapping the thickness of the Nesson anhydrite. Detailed mapping of structure (with ten foot contours), and of areal limits of specific porous units beyond field boundaries can indicate future trends in exploration activity.
Within the Duperow Formation, several upward shoaling cycles can be defined, each with a sealing anhydrite underlain by porous stromatoporoid-rich sucrosic dolomite reservoir. Unlike the Mission Canyon tidal flat sequences, these are quite regular and can be correlated over large areas. Not all cycles are productive, although most contain some porosity; the degree of dolomitization is variable and affects the reservoir quality. The situation is complicated by the limited availability of source materials and the numerous anhydrite seals which prevent vertical migration of oil to porous beds in every cycle.
Modern wireline log suites, computer generated log interpretations and cores provide a good framework for determining lithofacies and reservoir characteristics. These tools also allow for extrapolation of facies over a large area including other fields, such as Little Knife to the northeast and the Medora-Fryburg complex to the south.
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