Gas production climbs in Wyoming's Waltman field

Barrett Resources Corp., Denver, was moving in four rigs in mid-August to drill in the Cave Gulch area beneath the Owl Creek thrust in the east-central Wind River basin of Wyoming.

The U.S. Bureau of Land Management issued a decision on an environmental impact study of the area in early August, allowing development to resume, Barrett said. Waltman field, which contains the production on the Cave Gulch Unit, is about 50 miles northwest of Casper.

One of the rigs will be used to drill a 21,000 ft exploratory well to Pennsylvanian Tensleep and Mississippian Madison. One rig will begin development of Cretaceous Frontier, Muddy, and Lakota, and the other two are assigned to shallow Cretaceous Fort Union and Lance development, Barrett said.

Barrett, which has production elsewhere in the basin, reported Wind River basin production for the six months ended June 30 of 49,000 bbl of crude and condensate and 9.174 bcf of gas.

Several operators are developing Waltman field.

Wind River basin tight gas potential is largely undeveloped. The main tight gas formations are Paleocene Fort Union, Lower Cretaceous Frontier, and Upper Cretaceous Mesaverde (OGJ, Mar. 18, 1996, p. 102).

Recent completion

Barrett, Cave Gulch unit operator, in August completed the 16 Cave Gulch deep test in 32-37n-86w. The well reached TD 19,106 ft in mid-February 1997 and has undergone extensive tests.

It was producing into a sales pipeline after five days' flow testing at a stabilized 10.2 MMcfd of gas with 2,550 psi FTP on a 24/64 in. choke from Third Frontier sandstone. Measured reservoir pressure is 13,750 psi.

Third Frontier is 48 gross ft thick. Barrett stimulated the zone with a solvent to remove oil-based mud damage and ran a small gel and bauxite frac job.

Barrett earlier tested the naturally fractured but tighter Muddy sandstone. An initial unstimulated flow rate of 21.7 MMcfd fell to 6 MMcfd after seven days. The zone should deliver 3-4 MMcfd, natural, based on pressure tests and extensive flow tests, Barrett said.

Several other untested zones behind casing are to be added to the production stream once the Third Frontier's pressure declines to an acceptable safety level. The 50 ft thick First Frontier sandstone tested a significant gas flow while drilling and appears much better on logs than the Third Frontier. Fourth and Fifth Frontier sandstones are untested and appear productive on logs.

Previously reported attempts to stimulate and complete the deeper Lakota sandstone were unsuccessful due to mechanical problems combined with possible formation damage from oil based mud invasion during drilling. Lakota will be tested in the first development well to spud in September one mile north.

Barrett said last February that the No. 16 well encountered Frontier, Muddy, Lakota, and Jurassic Morrison and Sundance at least 1,100 ft structurally high to the four offset gas wells, three of which have produced from Frontier and one from Muddy, Lakota, Morrison, and Sundance (OGJ, Mar. 3, 1997, p. 90).

Further drilling

Numerous wells are planned or being drilled in the Waltman field area.

Barrett's planned 21,000 ft exploratory test is the 3-29 Mad-Cave Gulch-Federal, in 29-37n-86w, Natrona County, on the northwest side of Waltman field. The Lakota attempt, in the same square mile, is Barrett's 1-29 Lak-Cave Gulch-Federal. It is projected below 18,000 ft.

Barrett opened the subthrust Lance play in Waltman field in late 1994 at the 1 Cave Gulch-Federal, in 31-37n-86w. It has produced gas and condensate from Lance at 7,636-8,990 ft, Petroleum Information/Dwights LLC reported.

Other companies with wells producing or capable of production in the area include Chevron USA Inc., Marathon Oil Co., W.A. Moncrief Jr., Fort Worth, and Prima Energy Corp., Denver, and several others. Barrett's working interest in Cave Gulch Unit exceeds 85%.

Waltman field, discovered in 1959, has produced 135.7 bcf of gas, 512,760 bbl of condensate, and 350,130 bbl of water, PI reported. April output averaged 130 MMcfd of gas, 585 b/d of condensate, and 150 b/d of water from 24 wells.

PI noted that CIG Exploration Inc. in 1979 completed the Bullfrog Unit, in 6-36n-86w. Now operated by Barrett, it is shut-in after producing 3.36 bcf of gas and 22,800 bbl of water.

Producing zones were: Muddy at 19,830-872 ft, Lakota at 20,060-099 ft, Morrison at 20,226-338 ft, and Sundance at 20,455-510 ft. At the time, the well established a producing depth record for the Rocky Mountain area.