Marcellus and Utica Shale / by Norris McDonald

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Marcellus shale has become one of the world's largest natural gas fields and the Utica Shale - located a few thousand feet below the Marcellus - has become a new drilling target.  Marcellus Shale occurs in the subsurface beneath much of Ohio, West Virginia, Pennsylvania and New York.  Small areas of Maryland, Kentucky, Tennessee and Virginia are also underlain by the Marcellus Shale.

Utica shale underlies significant portions of Ohio, Pennsylvania, West Virginia, New York, Quebec and other parts of eastern North America.  In the subsurface, the Utica Shale is located a few thousand feet below the Marcellus Shale.

In 2011 the Energy Information Administration reported that the Marcellus Shale contained approximately 410 trillion cubic feet of technically recoverable natural gas.

The United States Geological Survey's mean estimates of undiscovered, technically recoverable unconventional resources indicate that the Utica Shale contains about 38 trillion cubic feet of natural gas, about 940 million barrels of oil, and 208 million barrels of natural gas liquids.

Of course, It is difficult to estimate the amount of gas in a rock unit that varies in thickness, composition and character, and is located thousands of feet below Earth's surface.

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The Utica Shale has not been extensively developed for two reasons: 1) its great depth over much of its geographic extent, and, 2) its limited ability to yield gas and oil to a well because of its low permeability. This is starting to change as horizontal drilling and hydraulic fracturing are used to stimulate production. These methods were not extensively used in the Utica Shale prior to 2010.

In central Pennsylvania, the Utica can be up to 7000 feet below the Marcellus Shale, but that depth difference decreases to the west. In eastern Ohio the Utica can be less than 3000 feet below the Marcellus.  Most of the drilling activity in the Utica Shale has occurred in eastern Ohio.  Most of the shale drilling activity in Pennsylvania has targeted the Marcellus Shale, which is above the Utica Shale.  (,