Estimated gas yield from Marcellus shale goes up

Penn State University geoscientist Terry Engelder said in a phone interview Monday that he now estimates 363 trillion cubic feet of natural gas could be recovered over the next few decades from the 31-million-acre core area of the Marcellus region, which includes southern New York, Pennsylvania, West Virginia and eastern Ohio.

Engelder and geologist Gary Lash of the State University of New York at Fredonia touched off a gas rush in the region last January with their study estimating that the Marcellus could yield as much as 50 trillion cubic feet of natural gas.

Geologists have long known about the existence of the Marcellus shale, but exploration there accelerated only recently when the price of natural gas rose high enough to make it economically feasible to use the advanced drilling techniques necessary to produce gas from the hard rock thousands of feet underground.

Production on the Marcellus gas field, or "play," is considered to be in the early stages, but the sheer size of it is drawing heavy interest from the exploration industry.

"It has the potential to be the biggest gas field in the United States," John Pinkerton, chairman and chief executive of Range Resources Corp., said last week in an interview at the Fort Worth, Texas-based company's office in western Pennsylvania.

Engelder first presented his new numbers in Pittsburgh last week at a conference on Appalachian gas sponsored by the energy information firm Platts. He said he based his revised estimate on new figures from Chesapeake Energy Corp., the nation's largest natural gas producer.

Oklahoma-based Chesapeake recently told investors and analysts that each square mile in the Marcellus could contain 30 billion to 150 billion cubic feet of gas. Engelder and Lash initially estimated 9 billion cubic feet per square mile.

Chesapeake also said the thickness of the gas-containing shale ranged from 50 to 300 feet, while Engelder and Lash assumed a thickness of 50 feet.

Applying his own calculations to numbers presented by Chesapeake, Engelder came up with his new estimate of how much gas the region might be able to produce over the next few decades, given enough time and money.