The most successful early tests in Washington and Allegheny County, Pennsylvania, were completed with slick-water gel fracs.Although these early water fracs were more effective than the foam treatments, these treatments were simply not large enough to establish the rates of production needed to achieve play commerciality on a broad scale.These shallow wells were used mainly for domestic and light industrial purposes and were extensively developed from the 1860s through the mid-1900s.The first major shale discovery in the Appalachian Basin was in 1921 in northeastern Kentucky, which established the Big Sandy field.To date, a total of more than 21,000 wells have been drilled in the Big Sandy field in eastern Kentucky, southern West Virginia, southern Ohio, and southwestern Virginia.The primary target in the Big Sandy field is the Upper Devonian Huron Shale, with contributions from the Cleveland, Rhinestreet, and Marcellus Shale intervals.Accurate data for these wells are scarce, but the likely black shale formations produced include the Dunkirk, Rhinestreet, Middlesex, and to a lesser extent the Marcellus.
By 1860, a series of shallow shale-gas fields were developed in a fairway along the Lake Erie shoreline extending from Fredonia, New York, southwest toward the city of Sandusky, Ohio.
Researchers involved in the EGSP identified the Marcellus Shale as a potential exploration target in the central and northern Appalachian Basin in the late 1970s.
Identification of the Marcellus Shale as a potential target encouraged operators to pursue development of the resource, and in the late 1970s and early 1980s, several unsuccessful attempts to establish commercial production from the Marcellus Shale were performed.
The Appalachian Basin has a well-established history of shale-gas development (Figure 1).
The discovery and commercial use of gas from Devonian shales in the early 1820s in Fredonia, New York, is generally recognized as the birthplace of the natural gas industry.