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T.J. Petta, 1980. "Silurian Pinnacle Reef Diagenesis-Northern Michigan: Effects of Evaporites on Pore Space Distribution", Carbonate Reservoir Rocks, Robert B. Halley, Robert G. Loucks
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Most of a 450 foot (150 m), gas-bearing Niagaran reef was cored by the Shell, St. Union 1-8. The well is located approximately in the center of the pinnacle reef belt (Fig 1). Three distinct facies described by Sears and Lucia (1979) are present in the core. The facies are, in ascending order, mud mound, coral-stroinatoporoid, and restricted marine.
Crinoid bryozoa mudstone-wackestone (Fig. 2) which contains stromatactis-like vugs is typical of the mud mound facies. A more diverse fauna including corals and stromatoporoids (Figs. 3 and 4) colonized the mound as it accreted upward from deeper water. Immediately prior to post-pinnacle evaporite deposition in the Michigan Basin a restricted fauna, mostly comprised of pentamerid brachiopods, inhabited the reef.
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Carbonate Reservoir Rocks
This core workshop is the product of an effort by the SEPM Carbonate Research Group to emphasize the value of careful core interpretation to hydrocarbon exploration and production programs. Initially conceived as a small conference the format was expanded in response to strong interest from the geologic community. The end result was a workshop including 14 core displays. The notes were intended as a guide but the thorough documentation of these cores will be of interest to many others.