The Tensleep reservoir, Torchlight field, Wyo., is nearing depletion by natural water drive and supplemental water injections after producing over 2.7 million bbl of oil. However, these two methods assume 100 per cent areal sweep efficiency, and reduction for areal sweep would result in close agreement with actual recovery. Predicted oil recovery by the Dykstra-Parsons and Stiles methods indicate recoveries of 46 and 50 per cent original oil in place, respectively. Oil recovery by supplemental water injections of 43 per cent of original oil in place will be comparable to recovery by natural water drive. Supplemental water injections have reduced reservoir life at least seven years. By Jan., 1965, the reservoir had been essentially depleted after producing 2,774,000 bbl oil. Oil response was immediate and reached a maximum rate of 1,785 BOPD in 1959. Supplemental water injection was started in Oct., 1957, to reduce reservoir life and increase oil rates. The difference is due to reservoir pressure being higher than that assumed in the prediction. Predicted rates are 10 to 15 per cent higher than actual rates. Comparisons are made between field producing rates and rates predicted by water influx theory. Field performance indicated the reservoir was producing by a limited water drive and would require over 25 years for depletion. After development, fluid producing rate and reservoir pressure declined rapidly.
The 33 degrees API gravity Tensleep crude was highly undersaturated, and hydraulically contained in the anticlinal reservoir by a tilted water table. 1, the Tensleep discovery well, was completed in 1947. The Torchlight field is located on the east side of the Big Horn Basin in Big Horn County, Wyo.
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