--> ABSTRACT: Geology of the Basin-Centered Gas Accumulation, Piceance Basin, Colorado, by Cumella, Stephen; #90026 (2004)
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Cumella, Stephen1
(1) Williams Production, Evergreen, CO

ABSTRACT: Geology of the Previous HitBasinNext Hit-Previous HitCenteredNext Hit Previous HitGasNext Hit Accumulation, Piceance Basin, Colorado

A very large Previous HitbasinNext Hit-Previous HitcenteredNext Hit Previous HitgasNext Hit accumulation in the Williams Fork Formation of the Mesa Verde Group is currently being actively developed at 10-acre density. Ten-acre density is necessary to develop a reasonable amount of the Previous HitgasNext Hit-in-place due to the very low (microdarcy) permeability and the highly lenticular nature of the fluvial sandstone reservoirs. Within the area of commercial Previous HitgasNext Hit production, Previous HitgasNext Hit is produced from a continuously Previous HitgasNext Hit-saturated interval of 1,500-3,000 feet. A transition zone of mixed Previous HitgasNext Hit- and water-saturated sandstones overlies the continuously Previous HitgasNext Hit-saturated interval. Pressure gradients, which can be as high as 0.8 psi/ft in the lower part of the Williams Fork in the structurally deeper part of the basin, decrease upward to hydrostatic gradients near the top of the continuously Previous HitgasNext Hit-saturated interval. Pervasive natural fracturing provides sufficient reservoir permeability to allow commercial production over 14-township area. This area is continually expanding as a result of current active Previous HitexplorationNext Hit for this Previous HitbasinNext Hit-Previous HitcenteredNext Hit resource. Overpressuring due to generation of large volumes of Previous HitgasNext Hit from interbedded coals and carbonaceous shales may have been important in fracturing the sandstones. During maximum burial and peak Previous HitgasTop generation, overpressuring may have been maintained beneath a regionally extensive top seal in the upper part of the Williams Fork Formation.

 

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.