Abstract

The Green River formation in the Utah Basin of eastern Utah is a series of low-permeability sands containing a viscous crude oil. Primary stimulation techniques involve the pumping of hydraulic fracture treatments. Usually several treatments are pumped per wellbore because, the sands are spread out over a large vertical interval. Typical treatments use a crosslinked Borate fluid with high proppant concentrations and moderate volumes of sand as proppant.

The operator's changes in fracture treatment design were evaluated through comparisons to offsetting well production responses. The results indicate a 65% improvement in early, six-month, oil recovery and improved effective stimulations versus prior development projects. These results are primarily due to increasing the fracture conductivity through more effective proppant placement. Descriptions of the fracture treatment designs and predicted fracture geometry using fracture computer models will be presented. The economic impact of the increased production response has added $60,000 of additional revenue to early response while fracture treatment costs have actually declined.

The paper will also detail the reservoir description work that has been performed to quantify the production response from individual sands in the Green River formation. This work will further improve economics by allowing true fracture optimization for individual treatments. The reservoir description technique uses standard openhole log suites and results in a prediction of in-situ formation permeability for individual sands. The technique has proven very accurate in predicting well production response and these results will be presented. The authors believe that the methodology used can be applied to similar reservoirs to achieve similar results.

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