From April through August of 2009, seven producing wells in the Spring Creek field in the Bighorn Basin of Wyoming were treated with chromium acetate crosslinked polyacrylamide in an attempt to reduce water production, lower fluid levels and achieve more drawdown, resulting in improved oil production. The wells were chosen because of their high productivity, high water cut, suboptimal operation because of pump limitations, and in some cases, marginal economics.

The volume of the gel treatments, which were pumped through tubing with a packer above the productive formations, ranged from 8000 bbls to 11,500 bbls depending on the theoretical maximum productivity of each well when pumped off. The Spring Creek field produces out of the fractured Tensleep sandstone, and the fractured Phosphoria carbonate. The main drive mechanism is bottom water, but reinjection of produced water contributes to some reservoir sweep.

After the seven wells were aggressively treated and returned to production, water rates were reduced by 72%, unfortunately oil rates were reduced by 56%. Following the treatments, however, the total oil production for the areas surrounding the treated wells had increased. It is believed that the increase in oil production is attributed to the diversion of the drive water to other unswept parts of the reservoir with higher oil saturation. The large size of the treatments and extent of penetration through the fractures played a significant role in accomplishing this diversion.

In similar wells treated with a smaller volume of gel, water reduction was not as significant, oil loss was not as great, and the increase in area oil production and added reserves was not as observable. This paper quantifies the favorable effects and economics of this larger more aggressive gel treatment strategy.

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