This paper is a study of hydraulic fracturing techniques used in the Converse IIA reservoir in the Lance Creek field, Niobrara County, Wyoming. The Permian Converse formation is composed of interbedded dolomites, anhydrites, shales, and sandstones. In the Lance Creek field, the upper Second Converse section contains an oil-productive sandstone at an average vertical depth of 4600 ft. The pay sand, known as the Converse IIA, is from 15- to 35 ft thick; the average porosity and permeability is 9% and 5 md, respectively. With the depletion of the formerly-prolific Leo and basal Sundance zones below their economic limit, many Lance Creek wells have been recompleted recently in the Converse IIA zone.

To enhance production from this moderate-permeability sandstone, hydraulic fracturing treatments have been performed on most of the Converse IIA wells in the field. A unique situation exists in that fluid and proppant volumes pumped in the treated wells are similar, but fluid and proppant types are varied. In this paper, we evaluate the response of the reservoir to the different treatment materials and techniques that have been used. Conclusions on the relative success of the different treatment options is substantiated by comparing treatment and reservoir data to production and well-history data.

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