Appalachian Basin

Historically one third of the wells drilled in the United States each year are drilled in the Appalachian Basin. Pennsylvania, Ohio and West Virginia consistently rank in the top five states, behind Texas and Oklahoma, in the number of wells drilled yearly. The reason for this high rate of drilling activity lie in the characteristics of Appalachian gas wells. The Geology of the Appalachian Basin yields a high success rate, 97%, for gas well drilling due to the presence of numerous potentially productive formations. The higher probability of drilling a productive well, typically long well lives, advancements in well completion technology and closeness to the northeast gas consumption markets have all contributed to maintain the attractiveness of Appalachian gas well drilling. These factors support continued drilling activity and an optimistic outlook for the continued growth of the gas industry in the Appalachian Basin.

The Commonwealth of Pennsylvania is under laid with a multitude of oil and/or gas producing formations. These formations, which include individual pay zones in a wide geographic area, have been under development since 1859. The Upper Devonian hydrocarbon producing area of Western Pennsylvania has historically been the most prolific in terms of drilling activity.

Hydrocarbon production has existed for at least one hundred years in this area of Western Pennsylvania, with early wells varying in depth from 1,200 feet to 4,200 feet. The early wells were usually completed as natural producers and generally exhibited small natural productivity. This was due to the lack of technology and methods of hydraulic stimulation at that time.

Some early well operators attempted to simulate their wells by "shooting" them with nitroglycerine in the open hole. This method was found to be a hit or miss operation at best. It is not usual in Western Pennsylvania to find new wells exhibiting virgin reservoir pressure and producing at rates much greater than the off-setting old wells that were completed as natural producers. This is because of the advanced completion technologies available today. During 1992, four hundred eighty four Upper Devonian gas wells were drilled in the five primary countries of interest. This represents 74% of the 653 Upper Devonian gas wells drilled in Pennsylvania during 1992. The most heavily drilled county was Indiana with 158 wells, closely followed by Armstrong with 141 wells, Clearfield with 97 wells, Jefferson and Westmoreland each having 49 wells drilled. Indiana and Armstrong counties alone accounted for 44% of the total number of Upper Devonian gas wells drilled. Over 90% of the wells drilled in the past twenty five years have been Upper Devonian tests.

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