Reservoir Characterization of the Wasatch Formation in the Hanging Rock Development Area, Southeastern Uinta Basin, Utah

Estes-Jackson, Jane E., Steven W. Shefte
McElvain Oil and Gas Properties, Inc, Denver, CO

The Hanging Rock development area comprises the western portion of Oil Springs field, located in T12S, R23-24E, Uintah County, Utah. It has added over 7.5 BCFG to the field since 1996. This area is located 12 miles southeast of and 2200 ft up dip from Natural Buttes field. Gas is produced from multiple, discontinuous, lenticular sandstones within the Tertiary Wasatch Formation at depths of 2500 ft to 4000 ft. The lateral and vertical distribution of individual reservoir units is difficult to predict. Wells drilled on 80-acre spacing have encountered sandstones that are not correlative to offset wells. Faulting also contributes to reservoir compartmentalization.

Completion technique is critical to the success of this play. Although the Wasatch reservoirs at Hanging Rock are slightly overpressured, they are also susceptible to water blocking. Fracture stimulation increases the relative permeability of the reservoir, which, in turn, increases water production. Therefore, wells are completed naturally, with no fracture stimulation. This practice enhances gas production by reducing water production, and minimizes completion costs. In general, wells that have been completed naturally are economic, whereas those that are fracture stimulated are not. With drilling and completion costs of $350,000 and gas prices at $3.00/MCF, these wells typically payout in less than one year.