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.
Evidence of Rapid Fluid Migration During Deformation, Madison Group, Wyoming and Utah Overthrust Belt Available to Purchase
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Published:January 01, 1985
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CitationJoyce M. Budai, 1985. "Evidence of Rapid Fluid Migration During Deformation, Madison Group, Wyoming and Utah Overthrust Belt", Rocky Mountain Carbonate Reservoirs: A Core Workshop, Mark W. Longman, Keith W. Shanley, Robert F. Lindsay, David E. Eby
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Abstract
The relationship between deformation-induced pressure solution and fracturing in carbonate rocks can be complex and may be interactive. Multiple episodes of pressure solution and fracturing are common in strongly deformed carbonate units such as the Mississippian Madison Group of the western Overthrust Belt. Paragenetic relationships in these rocks suggest that fractures both modify and enhance continued pressure solution by opening the host rock to fluid migration.
The composition of vein and stylolite mineralization may be used to evaluate the history of fluid migration during deformation. In the Madison carbonates, the earliest veins were filled by dolomite or calcite, while all subsequent veins were filled with calcite. Host limestone and dolomite are non-luminescent while filled veins are variably luminescent. The isotopic compositions of vein-filling calcite and dolomite are distinct from host rock compositions and document changes in fluid chemistry during burial and deformation. Taken together, the temporal change in mineralogy, luminescence and isotopic compositions of various vein-filling carbonate cements vs. host rock carbonates are strongly suggestive of rapid allochthonous fluid migration during deformation of the Madison Group in the western Overthrust Belt.