Looking for a structural play in a proven oil province? Check the undrilled anticlines on central Wyoming for potential.

Speaking at the American Association of Petroleum Geologists' annual conference and exhibition in Denver, Mike Pinnell, exploration manager for the Rocky Mountain region for Chief Oil & Gas LLC, offered the suggestion during a presentation in the Discovery Thinking session.

The paper was titled “Undrilled Laramide Anticlines in the Cordilleran Foreland of Wyoming Require Evaluation: Not All Will Contain Commercial Hydrocarbons. Which Ones Will? The Past is the Key to the Present.

The source rock is the Permian Phosphoria, which migrated hydrocarbons to the east where they were trapped in subtle structures.

Lost Soldier and Wertz fields on the Sweetwater Arch and the Bison Basin east of Lost Soldier have potential. Lost Soldier has produced 407 million bbl of oil and still produces 6,670 b/d of oil after 60 years of production.

Northwest and easily visible from Lost Soldier sits Green Mountain, the surface representation of a Laramide anticline that has yet to be tested by a well, he said.

Farther north in the Wind River Basin, Little Dome is a structural anticline that has produced no oil or gas, but nearby Winkleman Dome has produced 14 million bbl of oil, Pinnell added. That structure has 2,500 ft of closure.

Nearby Emigrant Gap Anticline, with 2,000 ft of closure, has never been drilled.

At Sheldon Dome, one well produced 550,000 bbl of oil from the Tensleep formation.

Typically, he said, Laramide structures offer good production unless they are on the flanks where production is marginal.

In response to a question from the audience, Pinnell said Chief Oil & Gas has no leases on Laramide anticlines he described.

In another paper during the same session, Pinnell and co-authors F.C. Moulton, G. Wood and G. Newman suggested, “Central Utah Thrust Belt: Covenant Field and the New Providence Field Discovery Portend Other, Exciting, New Structural Discoveries with Very Large Reserves of Both Oil and Gas.”

The Thrust Belt has been a prolific producer in places. In Canada, its 900-mile length holds some 42 Tcf of gas in place. It shows only minor production in Montana, but produces vast quantities of gas in southwestern Wyoming on the Absaroka Thrust. It has produced 2.1 Tcf of gas and 25 million bbl of oil in that state.

Also in Wyoming, the Labarge Anticline holds some 550 Bcf of gas in place per section, or some 23 Tcf of gas.

The Thrust Belt also continues through Wasatch, Sanpete, Sevier and Piute counties in Utah, but until a few year ago, operators didn't believe those counties contained economic production.

Then, Wolverine Gas and Oil discovered first Covenant and later Providence Field. Providence must be bigger than Covenant, because the company is drilling one-mile offsets, Pinnell said.

The company found 655 ft of gross, 289 ft net, pay from Navajo Sand at Providence and 487 ft of gross, 424 ft net, pay at Covenent and has drilled 15 wells at Covenant Field.

The Thrust Belt in Utah, he added, “is similar to Wyoming but probably better.”