--> Abstract: Reservoir Compartmentalization of a Cretaceous Valley-Fill Deposit, Dakota Formation, San Rafael Swell, Utah, by Mark Kirschbaum and Christopher Schenk; #90078 (2008)

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Reservoir Compartmentalization of a Cretaceous Valley-Fill Deposit, Dakota Formation, San Rafael Swell, Utah

Mark Kirschbaum and Christopher Schenk
U.S. Geological Survey, Denver, CO

Valley-fill deposits form a significant class of hydrocarbon reservoirs in many basins in the world. Maximizing recovery of fluids from these reservoirs requires an understanding of the scales of fluid flow heterogeneity present within the valley-fill system. This study investigated a well-exposed unit of the middle to upper Cenomanian Dakota Formation in the San Rafael swell of central Utah for the purpose of documenting the major forms of compartmentalization. The Dakota consists of two major complex units: 1) a lower amalgamated sandstone dominated by large-scale cross strata with several individual sandstone bodies ranging in thickness from 8 to 28 ft and ranging in width from 115 to 150 ft, and 2) an upper unit comprised of numerous mud-encased lenticular sandstones, dominated by ripple-scale strata, in bedsets ranging in thickness from 5 to 12 ft. Potential reservoirs in this valley fill are compartmentalized with respect to fluid flow by 1) mudstone interbeds that separate potential reservoir sandstones, 2) sedimentary structures with directional permeabilities that vary from bed to bed, and 3) diagenetic variations that create significant porosity and permeability variations between sandstones (.007 to 2000 mD). The different scales of fluid-flow compartmentalization present a challenge to maximizing hydrocarbon production from these types of deposits.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas