Gas Cycling in the Lookout Butte Rundle Pool

The Lookout Butte condensate-bearing gas accumulation is contained in afractured thrust block of Rundle strata at a depth of 12,200 feet. Themoderately sour gas initially contained 106 barrels of pentanes plus permillion cubic feet of well effluent. As studies indicated that only 27.5 percent of the original pentanes plus in place were recoverable by normal pressuredepletion, a gas cycling scheme was initiated in 1963 to increase condensate recovery. Gas is produced from four wells, condensate is removed and stabilized, and sour, relatively dry gas is injected into a single well at the north end of the pool. It is anticipated that 33.7 per cent of the originalpentanes plus in place will be ultimately recovered if the pool is cycled at 40MMcf/D prior to pressure depletion. The prediction methods and performance todate are discussed. The effect of fractures on cycling performance isimportant. Performance in Lookout Butte during 18 months generally confirms assumptions regarding the effectiveness of the fractures. The elongated shapeof the reservoir is expected to result in a favourable areal sweep. This configuration also permits flexibility in the event that a second injection well is required in the future. Introduction The Lookout Butte Rundle gas pool is located in the extreme southwestern corner of Alberta between the Pincher Creek Rundle gas pool and the International Boundary, as shown on Figure 1. The pool was discovered in1959 by the drilling of B.A. Lookout Butte 11–31, in Lsd. 11-31-1-28 W/4, which encountered gas-bearing Rundle at approximately 12,000 feet. Seven wells were subsequently drilled, which resulted in four producing gas wells, two marginal gas wells and one abandonment. The Lookout Butte Rundle Unit No.1 became effective in August, 1963, at which time gas cycling commenced. Reservoir Characteristics I. Geology The Lookout Butte reservoir is a thrust block of Rundle strata, strikingnorth-northwest, dipping west and plunging gradually northward. Maximum elevation of the thrust block above the regional elevation of the Rundle is approximately 1,500 feet.