Abstract

The Greater Natural Buttes Field (GNB) of the Uinta Basin, located in northeastern Utah, was discovered in 1955. It has an aerial extent of approximately 400 square miles and as of December 2006 was producing over 545 MMCFGPD. Production is co-mingled primarily from sandstones of the Upper Cretaceous Mesaverde Group and Paleogene Wasatch Formation. The productive units are comprised of stacked, highly lenticular, tight, fluvial sandstones, interbedded with non-marine, organic-rich siltstones and shales, and thin coal seams.

A west-northwest trending “Fairway” located in the northern part of the field is a “sweet spot,” that contributes significantly to the overall production of the GNB. In an effort to develop and extend GNB to the south, 36 wells were sporadically drilled in the “Love Area” (T11S, R21E) beginning in 1960, but most (22) were drilled in 2006. The average estimated ultimate recovery of the most recent wells is 0.95 BCF/well, whereas those wells in the “Fairway” average 2.29 BCF/well.

Several geologic factors account for the lower production in the Love Area. In GNB, regional vitrinite reflectance data indicate a decrease in thermal maturity from north to south, which corresponds with a decrease in the number of gas-charged sandstones in the Wasatch and Mesaverde. The same geologic conditions that affect production in the Love Area also exist throughout the “southern flank” of GNB, which extends from the Green River on the west (R19E) to approximately R24E. A methodology that couples thermal maturity variability in regional context along with formation evaluation to identify the gas column of productive sandstones in a stacked, multi-storied tight (low porosity and permeability) sandstone system can be a useful tool for exploration and development in similar geologic provinces elsewhere.