Depositional Facies and Porosity Development in Lower Ordovician Ellenburger Dolomite, Puckett Field, Pecos County, Texas1
Published:January 01, 1980
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R. G. Loucks, J. H. Anderson, 1980. "Depositional Facies and Porosity Development in Lower Ordovician Ellenburger Dolomite, Puckett Field, Pecos County, Texas", Carbonate Reservoir Rocks, Robert B. Halley, Robert G. Loucks
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The Ellenburger Dolomite in the Puckett Field, Pecos County, Texas has produced nearly 2.6 Tcf of gas since discovery in 1952 from a depth interval of approximately 12,000 to 15,000 ft (3,660 to 4,570 m). Estimated ultimate gas recovery is 3.3 Tcf. Production is from a faulted anticlinal trap.
The Ellenburger facies are interpreted to have been deposited in several marine environments similar to those that occur around western Andros Island, Bahamas: subtidal, intertidal/supratidal channel belt, and supratidal. These facies form cyclical deposits totalling over 1,300 ft (400 m) thick. During Ellenburger sedimentation there were many periods of subaerial exposure which resulted in the formation of diagenetic terrains represented by poorly formed soil horizons and solution-collapse breccias up to 50 ft (15 m) thick. With deep burial, tectonic stresses produced fine fractures in much of the Ellenburger section.
Porosity in the Puckett Field averages 3.5 percent with a maximum of 12 percent. Permeability ranges from 0 to 169 millidarcys, but the most common range in permeability is from 10 to 50 millidarcys. The porosity network in the Ellenburger Dolomite consists of isolated zones of breccia porosity and intercrystalline porosity interconnected by open fractures.
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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.