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Drillers set sights on shale reserve deeper than the Marcellus

| Tuesday, Feb. 22, 2011

Another underground strip of shale in Pennsylvania, much deeper than the Marcellus formation, is drawing attention from natural-gas drillers.

Utica shale has potential, like Marcellus, to become a major fuel resource. The rock layer stretches far beyond the edges of the Marcellus, covering most of Pennsylvania, New York and West Virginia, along with eastern Ohio and parts of other states.

"A number of companies are taking a careful look at this shale, and in eastern Ohio there's been a fair amount of leasing" for well development, Penn State University geosciences professor Terry Engelder said Monday.

Consol Energy Inc. drilled a Utica shale well last year in Belmont County, Ohio, that generated 1.5 million cubic feet of gas over 24 hours -- impressive for a well where production wasn't stimulated, spokeswoman Laurel Ziemba said.

"It's actually higher than the rate from any of our vertical Marcellus wells" where production was triggered, she said. Cecil-based Consol plans to spend $35 million this year to drill about six exploratory Utica wells.

Range Resources Corp., a Fort Worth company with Appalachian offices in Cecil, is drilling in the Utica formation. Range drilled the first commercial horizontal well in the Utica formation in Southwest Pennsylvania, spokesman Matt Pitzarella said.

Chevron Corp. completed its $4.3 billion acquisition of Atlas Energy Inc. of Moon last week, giving the energy giant access to 623,000 acres of Utica shale resources. The company isn't specifying its plans for Utica shale, Chevron spokesman Nate Calvert said.

The Marcellus shale formation that sparked a rush of drillers to Pennsylvania and other Appalachian states averages 7,000 feet deep, and the older, thicker Utica layer runs 2,000 or more feet below that. The black Utica shale, 500 feet thick in places, dates 440 million to 460 million years.

Some geologists estimate the Marcellus formation has 50 trillion cubic feet of recoverable gas, enough to supply the East Coast for 50 years.

Although it hasn't been studied enough to determine its potential, Utica shale has shown the ability to support commercial gas production, a report in website said, and depending on how much of it might yield fuel, it could be larger than any known gas field.

Gas producers could drill down and then horizontally and inject high-pressured water, sand and chemicals to fracture the shale and free gas deposits, just as they do in Marcellus fields, Engelder said.

The additional depth isn't a hindrance, he said. "There's the Haynesville formation in Louisiana, where drillers are going as deep as 13,000 feet using the same technology," Engelder said.

Rock formations in the Appalachian basin tend to be thickest in the east and thinner toward the west, the report said. The Utica is about 7,000 feet below the Marcellus in central Pennsylvania, but less than 3,000 feet below it in eastern Ohio. In Western Pennsylvania, the Utica layer runs 11,000 to 12,000 feet deep.

Although the two gas-producing shale layers overlap, production companies could focus on different regions.

That's because certain parts of each shale formation will yield more fuel, based largely on temperature and pressure histories, Engelder said. His analogy: Shale that remained cooler, like a piece of underdone toast that won't melt butter, won't yield much gas, nor will a too-hot formation that burned off its gas, like blackened toast.

Rock that reaches 190 degrees Fahrenheit generates oil and some gas, he said. The top heat for creating, and not destroying, gas is 480 degrees.

Much of the Utica shale in that ideal pressure and temperature range stretches from the northwest Pennsylvania town of Titusville, where an oil boom began 150 years ago, to Columbus, Ohio, Engelder said.

Tom Murphy, co-director of Penn State's Marcellus Center for Outreach and Research, said Utica gas could have a higher British thermal unit, or BTU, content than Marcellus gas, making it more marketable.

"The southeastern part of Ohio right now is being explored for Utica shale gas," Murphy said, and some work is occurring in West Virginia. Landowners who lease mineral rights typically strike deals for producers to drill "all the way down" past the Marcellus to other layers of rock, he said.

Range Resources plans to drill a few more wells this year in the Utica and Upper Devonian shale layer, which is above the Marcellus. Gas producers potentially could drill multiple layers of wells in the future, all from the same spot, Pitzarella said.

"The Utica and Upper Devonian may combine to be as large as the Marcellus" in terms of recoverable gas, he said.

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