Rocky Mountain Carbonate Reservoirs: A Core Workshop

This core workshop was organized to give geologists from across the country and around the world the opportunity to see a wide variety of carbonate reservoirs as well as some carbonate source rocks from the Rocky Mountain region. Cores displayed at the workshop range in age from Cambrian to Cretaceous and come from a number of the major oil-producing basins in the Rocky Mountains. Depositional facies represented in the cores range from sabkhas and tidal flats through algal and coral buildups to relatively deep water chalks. Dolomite and evaporite minerals are important in approximately half the cores described; the others are dominantly limestone. Porosity of many different types is discussed. Diagenesis, or lack of it, has played a major role in forming virtually all the reservoirs. Thus, the workshop offers the chance to observe and study a wide variety of depositional and diagenetic textures in a number of economically important rock units.
Depositional Environment and Diagenesis of the Red River Formation, “C” Interval, Divide County, North Dakota and Sheridan County, Montana Available to Purchase
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Published:January 01, 1985
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CiteCitation
Douglas G. Neese, 1985. "Depositional Environment and Diagenesis of the Red River Formation, “C” Interval, Divide County, North Dakota and Sheridan County, Montana", Rocky Mountain Carbonate Reservoirs: A Core Workshop, Mark W. Longman, Keith W. Shanley, Robert F. Lindsay, David E. Eby
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Abstract
Data from the “C” interval of the Ordovician Red River Formation in Divide and Sheridan counties show depositional environments of the “C” burrowed carbonate, “C” laminated carbonate, and “C” anhydrite are remarkably persistent. Diagenetic events, however, are highly localized, and dolomitic porosity is discontinuous.
Environmental conditions changed during deposition of the Red River “C” interval. At the base of the interval is a burrowed carbonate deposited in a well-circulated, subtidal, normal marine environment. Gradually a restricted subtidal, relatively quiet water environment developed and the “C” laminated carbonate was deposited. Intertidal conditions may have existed intermittently. The sequence is capped by the “C” anhydrite deposited in a hypersaline, subtidal restricted environment. Red River paleotopographic highs coincide with “C” laminated carbonate thins and contain vertical microfractures healed with anhydrite. In contrast to laterally persistent dolomite of the “C” laminated mudstone, dolomite of the “C” burrowed carbonate is discontinuous. Anhydrite crystals within the “C” burrowed carbonate are always associated with dolomite and may have been derived from downward percolating sulphate-rich brines from the overlying “C” laminated dolomite, or “C” anhydrite.