Yellow Creek field extends from Sec. 11, T14N, R12W, 5.5 mi (9 km) northeast to the city of Evanston, Wyoming. The producing structure is a northeast-trending anticline on the hanging wall of the Medicine Butte thrust, an imbricate of the Late Cretaceous Absaroka thrust. Gas and condensate are produced from fractured Middle Jurassic Twin Creek Limestone at depths from 5,750 to 6,736 ft (1,725 to 2,020 m). The pay zones are estimated to have only about 2% porosity, and the thickness of the hydrocarbon column is at least 670 ft (201 m).

The first test, Utah Southern 1 Hatch, was off structure in SW¼ SE¼ NW¼, Sec. 28, T6N, R8E, Summit County, Utah, and abandoned in 1952 in Jurassic-Triassic Nugget Sandstone at a depth of 8,637 ft (2,591 m). No shows were reported. In 1976 Amoco drilled the discovery well, Amoco-Gulf WI Unit 1, in SE¼ SW¼ SW¼, Sec. 2, T14N, R121W, to 8,063 ft (2,419 m) in the Nugget. Initial flowing potential of 120 BOPD and 2.75 MMCFGD was obtained from the Twin Creek. In 1977 Amoco 1 Champlin 375 Amoco A, in SW¼ SE¼, Sec. 17, T15N, R120W, within the city limits of Evanston, became a Twin Creek discovery called Evanston field. Recently this well was completed for 222 BOPD and 1.48 MMCFGD. Subsequent discoveries between Yellow Creek and Evanston by Mountain Fuel, Mesa, and Amoco in 1978 indicate a single field. Currently, Yellow Creek has six successful completions with a combined

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IP of 2,254 BOPD and 21.8 MMCFGD. Three wells are testing and only two wells are known dry holes.

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