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The Corcoran and Cozzette sandstones (Campanian) are members of the Price River Formation within the Mesaverde Group of the Piceance Creek basin, and consist of marginal-marine facies between the underlying Mancos Shale and the overlying continental Mesaverde. Log-interpreted facies within the Corcoran-Cozzette vary from shale with thin siltstone to sandstone interbeds (shelf to lower shoreface), through upward-coarsening sequences (upper shoreface to foreshore), to interbedded thin coal, sandstone, and shale (alluvial plain to bay or lagoon). Plateau and Shire Gulch are the largest fields that produce gas from low-permeability (0.002-0.08 md), fine-grained to very fine grained sandstone of the Corcoran and Cozzette (over 8.4 bcf produced through 1982).
Within these fields, 7 distinct northeast-trending strandplain and barrier units have been identified. Strandplain sandstones form the lower half to two-thirds of each member, and barrier sandstones form the upper depositional units. Net sandstone thickness of the strandplain units increases from less than 20 ft southeast of the fields to more than 80 ft within Plateau field. Along the southeastern Plateau field margin, upper units in each member contain 30-55 ft thick sandstones that repeat the shoreface sequence.
Most completions are in the lower (39%) and upper (33%) Corcoran, whereas the lower and upper Cozzette each account for 14% of perforated intervals. The underlying Mancos Shale and overlying coal may account for the greater gas production of the Corcoran. Gas productivity of individual depositional units cannot be defined due to commingled production from multiple intervals in most wells.
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