Exploration and men's minds

Feb. 20, 2012
Geologists mulling the world's great discoveries of 2011 might be reminded of basins they have explored without making a big find. Perhaps the Great Basin is one of those places.

Geologists mulling the world's great discoveries of 2011 might be reminded of basins they have explored without making a big find. Perhaps the Great Basin is one of those places.

Shell stunned the industry in 1954 with the discovery of Eagle Springs field in Railroad Valley, Nye County, Nev. Then 145 exploratory wells later came Trap Spring field, and in 1983 Northwest Exploration Co. discovered Grant Canyon field, which has produced 21.25 million bbl of oil from 4,400 ft.

Then there was another hiatus until Wolverine Gas & Oil Co. announced the discovery of Covenant field in Utah in May 2004.

With natural gas out of favor because of the price and acreage positions staked out in the popular US unconventional plays, operators may choose to pursue some of the world's lesser known oily geological objectives.

Central Utah thrust belt

Wolverine's Covenant and Providence discoveries, at the transition between the Great Basin and Colorado Plateau, drew Occidental Petroleum Corp. to take a large position on the thrust belt in 2007.

Oxy USA's discovery in Kern County, Calif., is more public than the Utah play, but these days Oxy is said to be participating in several exploratory wells along the thrust belt.

One is a deep test in Covenant field, the 20-5 well being drilled directionally from NE NW 20-23s-1w, Sevier County, under completion in early February. In which zone(s) completion is being tried is confidential.

Wolverine and Oxy are drilling the Denmark Wash 15-2 well, in 15-21s-2w, Sevier County, 13 miles north-northwest of Covenant field. The well was supposed to be drilled to the White Rim formation just below Permian Kaibab at around 16,995 ft.

The firms also spudded the Painted Rock 29-1 well, in SE SW 29-17s-1w, Sanpete County, 33 miles north of Covenant, in 2009 with a Canadian rig that took it to about 3,000 ft. A bigger rig was to deepen it, perhaps to Mississippian, although the permit is for the Permian Kaibab at 14,000 ft. Further progress hasn't been disclosed.

Wolverine and Oxy also permitted a wildcat at the Twist Canyon prospect, to be drilled directionally from 21-21s-1e, Sevier County. This well has not spudded.

Conventional and not

The greater Great Basin contains an array of oily conventional and unconventional geological objectives.

Geologists Alan Chamberlain and S.K. Bhattacharjee described the Pilot shale in a recent article (OGJ, Nov. 7, 2011, p. 82). They said the Pilot is at least 140 ft thick under 45 million acres of the 71 million acres in the eastern Great Basin.

Mike Pinnell is a consulting geologist in Salt Lake City who was with Chief Oil & Gas LLC exploring the Central Utah thrust belt until Chief closed its office in September 2011. Pinnell's previous employer, Pioneer Oil & Gas, a private Salt Lake City independent, had an encounter with oil in the Pilot shale in the 1990s.

OGJ published an article by Pinnell after Pioneer found oil seeping from the Pilot shale at the Yankee Mine in the Alligator Ridge mining area in Nye County, Nev. (OGJ, July 15, 1991, p. 74).

Pinnell believes the Pilot shale has big potential.

"Since we found oil in it that was still liquid at the mine, the chances of oil deeper is a good bet. There are actually quite a few wells that have been drilled to this horizon.

"You must go through the Pilot to get to the (Devonian) Guilmette. A lot of Guilmette wells were drilled in Nevada looking for more Grant Canyon fields. Pioneer, my old company, drilled a lot of them," Pinnell noted.

"As I recall, the oil in the gold mine was actually in a sandy interval of the Pilot. This would make it a little like the Bakken of the Williston basin, where there is a sandy interval that is the usual goal of the horizontal drill bit. But in Nevada, the sandy interval is not pervasive."

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