Oolitic Tidal-Bar Reservoirs in the Mississippian Greenbrier Group of West Virginia
Gregory T. Kelleher, Richard Smosna, 1993. "Oolitic Tidal-Bar Reservoirs in the Mississippian Greenbrier Group of West Virginia", Mississippian Oolites and Modern Analogs, Brian D. Keith, Charles W. Zuppann
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In the Rhodell field of southern West Virginia, initial potentials of oolitic reservoirs in the Greenbrier Group commonly exceed 2.0 MMCFGD of natural gas. The major reservoir, an oolitic member of the Union Limestone, stands out as distinct northwest-trending thicks, comparable in size, shape, and location to modern tidal bars. They formed along the hinge line that separated a rapidly subsiding basin from a stable shelf. Individual bars have 15-30 ft (4.6-9.1 m) of net thickness with greater than 6% porosity, and the producing zones are ooid grainstones with a mean log porosity of 9.5% and permeability of up to 0.15 md. Ooids were generally altered to microrhom- bic low-magnesium calcite during meteoric diagenesis and developed considerable intragranular microporosity. Reservoir permeability is greatly enhanced where ooids have undergone chemical compaction, which produced long contacts between neighboring microporous grains.
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A coincidence of tectonic, eustatic, and geochemical conditions resulted in substantial deposits of oolitic limestone during later Mississippian time in the continental United States. These oolitic limestones have formed petroleum reservoirs with favorable primary and secondary recovery characteristics. Significant potential reserves in stratigraphic traps remain to be discovered and developed in these reservoirs.