Wildcats Planned for East Flank of Big Horn Basin

Big Horn County, Wyoming

Thermopolis, Wyo.–based Gas Ventures LLC is waiting on state approval to drill a pair of wildcats on the eastern flank of Wyoming’s Big Horn Basin. Located in Big Horn County, the company is proposing to drill the Bonanza Draw #1-27, se-sw 27-49n-91w, and one section to the west, the Bonanza Draw #1-28, ne-ne 28-49n-91w. These proposed wildcats are projected to evaluate the vertical Pennsylvanian Tensleep at depths of 4,210’.

The most northerly of these ventures, the Bonanza Draw #1-28, is located nearly a half-mile east of a shallow dry hole drilled 77 years ago by Yale Oil Corporation. The Blakesley B-032691 #1, ne-nw 28-49n-91w, bottomed in the Lower Cretaceous Thermopolis shale at a depth of 1,705’. No cores were cut or tests were conducted, and the attempt was plugged in 1934.

A similar distance to the southwest, Amerada Petroleum drilled a failure at the USA-Neal #1, nw-se 28-49n-91w. This test reached the Permian Phosphoria at a depth of 4,797’. Although no drillstem tests were conducted, the company did cut a core in the Phosphoria from 4,729’ to 4,777’, in which bleeding oil was noted. No production casing was run, and the well was abandoned in 1953. Log tops of this dry hole include the Lakota at 2,942’, Sundance at 3,294’, Dinwoody at 4,646’, and the Phosphoria was picked at 4,704’ from a KB elevation of 4,352’.

The closest production to the Bonanza Draw #1-28 is roughly 1.5 miles to the north at Manderson Field, a stratigraphic-type–trap that is located on a northwest-plunging anticlinal nose. Discovered in 1951, this multi-pay oil and gas pool currently produces from the Frontier, Mowry, Muddy, Octh Louie, Peay, Phosphoria, and Tensleep. Cumulative production for this reservoir exceeds 5.3 mmbo and 88.1 bcfg.

Jumping almost a mile to the southeast, Gas Ventures’s second planned wildcat, the Bonanza Draw #1-27, spots approximately a half-mile east of a test drilled by Coastal Oil and Gas at the Federal #1-27-49-91, sw-sw 27-49n-91w. This dry hole bottomed in the Tensleep at a depth of 4,499’ and was plugged in 1991. One drillstem test conducted in the Tensleep across the interval at 4,369’–4,387’ recovered 273’ of slightly mud-cut water and 2,011’ of water, with the sampler containing 2,150 cc of water. No additional testing was performed, and the well was abandoned. Log tops of this dry hole include the Muddy at 2,066’, Dakota at 2,382’, Morrison at 2,620’, Dinwoody at 4,040’, Phosphoria at 4,090’, and the Tensleep came in at 4,350’ beneath a KB elevation of 4,310’.

Approximately a quarter-mile southwest of the Bonanza Draw #1-27, Dominion E&P drilled a duster at the Anne #1, se-nw 34-49n-91w. This Tensleep wildcat went to a depth of 4,765’. No cores were taken or test conducted in this prospect, and it was abandoned in 1987.

The nearest production to the Bonanza Draw #1-27 is almost a mile to the east at Bonanza Field, a stratigraphic-trap that has produced more than 42.3 mmbo since 1950. This reservoir is currently averaging nearly 2.5 k bo and 621 k bw per month from 12 active wells, with all production coming from the Tensleep.