?Utah’s Mancos, one of the Rocky Mountain region’s thick, overpressured gray shales, has been receiving strong attention from Uinta Basin operators.

The Uinta is rich with such objectives as Wasatch, Mesaverde and Blackhawk gas-prone sandstones, and production has been growing robustly from major development programs in these intervals. Recently, drillers have been pushing wells deeper into the extensive Cretaceous section, investigating potentials in the Mancos and underlying Dakota sandstone.

The interbedded siltstones and shales of the Mancos reach up to 3,500 feet in thickness, and are found at depths below 13,000 feet in the heart of the basin. Operators had been drilling 1,000 feet or so into the shale to intersect the silty Mancos B interval, and commingling it with uphole objectives. More recently, companies have been drilling the entire section and stage-fracturing throughout.

Increasingly, companies are taking wells completely through the Cretaceous and into Jurassic Morrison. There’s a movement afoot to consider the Mancos as a stand-alone objective, perhaps one that could be induced to produce via horizontal wells.

“We believe the Mancos has the potential to become the hottest shale-gas play in the Rockies, and it adds to the significance of the Uinta Basin resource play,” says Eric Noblitt, partner of Park City, Utah-based Stonegate Resources LLC.

“Companies have focused on vertical wells because the Mancos shale section is so thick,” says Jason Blake, consulting geologist for Stonegate. “The technology of stage fracturing has opened up this play.”

Stonegate has assembled a 7,200-acre multi-pay prospect in Uintah County. Its Three Rivers project, which is ringed by deep drilling activity, lies on the north side of Natural Buttes Field. “We think that the Mancos and Dakota plays are of particular interest in our acreage,” says Noblitt.

In Natural Buttes, Salt Lake City-based Questar Corp. is in the midst of a major Mancos and Dakota effort. The company drilled 17 such tests in 2007. This year, it’s running six rigs and plans to drill 33 Mancos/Dakota wells. Questar has advised investors that wells completed in Wasatch, Mesaverde, Mancos and Dakota recover from 2.7- to 4.7 billion cubic feet equivalent each.

There’s also considerable Mancos activity to the west, in the vicinity of Monument Butte Field. Denver-based Gasco Energy has a busy deep program on the eastern side of the field in its Riverbend area.

To date, Gasco has drilled 11 wells into the Mancos and two into Dakota. Since it began targeting the shale in mid-2007, it has completed eight wells in the Mancos. In testament to the multi-pay nature of the Uinta Basin, six of those wells are completed or recompleted in additional uphole zones.

Previously, Gasco estimated that the Mancos added between 600 million and 1.15 Bcf in recoverable reserves to a multi-pay Riverbend well. Now it thinks improved stimulations are upping those Mancos production volumes.

Gasco recently drilled its #23-16 Gate Canyon State to Morrison. The 16,610-foot well encountered geopressuring, flares and gas shows in Mesaverde, Mancos, Dakota and Morrison. Completion work is in progress. The company currently has two rigs at work at Riverbend, and drills all its wells at least to Upper Mancos.

Within Monument Butte, Houston-based Newfield Exploration participated in two wells that tested Upper Mancos in late 2007. The company is in a deep-zone exploratory venture with Red Technology Alliance that covers 71,000 net acres in the field. In addition, Newfield holds 10,700 net acres in an exploitation area adjacent to Gasco’s area. Newfield plans five operated and five nonoperated deep Mancos wells on that slice of land this year.

Farther southwest in northeastern Carbon County, Calgary-based operator Petro-Canada has a deep drilling program under way. Field reports indicate the company has made a discovery, but that is not confirmed.

Fort Worth-based operator XTO Energy is also interested. The company has noted that Mancos is a target for potential acreage expansion. It plans several deeper tests to evaluate the Dakota and Mancos on acreage it owns in Natural Buttes. It is expected to try some horizontal Mancos drilling.

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