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Abstract: A Reservoir Characterization of the Hay Reservoir Area

Greg P. Anderson

Hay Reservoir is located in the Red Desert portion of the Greater Green River Basin, Sweetwater County, Wyoming. This Upper Cretaceous Lewis field was discovered by Davis Oil in 1976. Two Lewis sandstone intervals are commercially productive in this area, with average per well reserves of 4.5 BCF and 85 MBC. The reservoirs have an average net pay thickness of 36 feet (11 meters), and are encountered at an average depth of 9,900 feet (3,018 meters). In 1989, the estimated ultimate recovery of the Hay Reservoir area was under 90 BCFG and 1.7 MMBC. Since then, 26 development wells have been completed and the area has now produced over 92 BCFG and 1.8 MMBC. Currently, the estimated ultimate recovery for this area is 200 BCF and 3.5 MMBC.

The reservoir sandstones are fine grained, poorly sorted, sublithic arenites. These classic tight-gas sands have core porosity averaging 8.4 percent and permeability averaging 0.07 md. The two reservoir sandstones were deposited as basin-floor fan turbidites, and are located at an identifiable break in slope at the toe of clastic wedges. The sandstones are massive, but form heterogeneous reservoirs that are positioned to pinch out up-dip forming classic stratigraphic traps. The highest permeability is encountered at the up-dip edge due to hydrocarbon emplacement terminating authigenic clay diagenesis.

An integrated geologic/engineering study of this field was completed with the interpretations combined in a field-wide reservoir simulation. The simulator is used to identify the optimum location of high productivity wells in under-drained cell areas.

AAPG Search and Discovery Article #90959©1995 AAPG Rocky Mountain Section Meeting, Reno, Nevada