Located more than a mile beneath Appalachia, covering parts of West Virginia, Ohio, Pennsylvania, and New York, lays a mostly untapped reservoir of natural gas that could hold the key to the nation’s energy future. The total area covers 54,000 square miles and could contain as much as 50 trillion cubic feet of recoverable natural gas, according to a recent study by researchers at Penn State University and the State University of New York. According to the Energy Information Administration, i n 2007 the U.S. consumed approximately 23.1 trillion cubic feet of natural gas and produced the same approximate 23.1 trillion cubic feet, with only 20.1 trillion cubic feet making it to market. The U.S. made up the difference between consumption and production by receiving imports from places such as Canada. The Marcellus shale is likely to assist the U.S. into becoming self sufficient.

Geologists, engineers, and energy companies have known for decades about the natural gas located in the Marcellus Shale. Only recently have they discovered a possible, although expensive, way to extract it from the thick black shale 6,000 feet underground. Energy firms must decide whether the cost of obtaining the natural gas is worth the huge investment. The multimillion-dollar question posed is whether deep well and horizontal drilling technology can consistently produce natural gas from the shale hundreds of millions of years old. Corporate players looking for natural gas in Marcellus shale include Range Resources, Southwestern Energy, Chesapeake Energy, and Cabot Oil and Gas.

Companies intend to extract natural gas from the Marcellus Shale by drilling down to a depth of about 6,000 feet or more, before making a right angle and drilling horizontally into the shale. A well of this design could cost a company $3 million to build, excluding the cost of leasing the land. Scientists and engineers had long postulated that the Marcellus shale served as a source for shallow wells dug by conventional methods. Previous attempts to extract gas conventionally from the Marcellus have produced meager results.

A series of seams or fractures in the Marcellus Shale could hold the answer. If mapped, these fractures could look like a matrix or grid of a city with nearly perfectly laid out square blocks. Drilling horizontally into seams and fractures could help give the natural gas an outlet to escape. Companies could also use a technique in which water pressure is used to create new openings in the dense fractures to allow the natural gas to flow into the newly drilled horizontal well.


Marcellus shale formation. Photo Courtesy of Wikipedia

Companies began reaping the benefits from horizontal drilling technology a decade ago in the Barnett Shale, a 5,000-square-mile field in Texas which has produced about 1.2 billion cubic feet of natural gas a day. Forecasts have called for production in the Barnett natural gas field to reach 1.7 billion cubic feet. Success from the Barnett Shale inspired companies to explore other potential natural gas reserves in the United States, including the Marcellus Shale.

One of the first wells to explore the shale owned by Exco Resources near Snow Shoe, Pennsylvania, was planned for 3,500 feet. The drillers only went to 1,700 feet and hit a fault. That fault allowed for the extraction of gas at a rate of 1 million cubic feet a day, according to the company’s third quarter results statement. Demand for alternative energy is focusing attention on natural gas and the Marcellus Shale.

Source: Appalachia tantalizes natural gas drillers, February 2, 2008

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