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Since the discovery of gas in the Oriskany sand in north-central Pennsylvania in 1930, nineteen deep wells have been drilled to the Oriskany on seven major folds 30-40 miles southeast of the old oil and gas fields in northern West Virginia. This exploratory drilling has resulted in the discovery of two gas fields known as the Terra Alta and Canaan Valley fields situated respectively 25 and 50 miles south of the Summit field in Fayette County, Pennsylvania. The Terra Alta field has eight gas wells and the Canaan Valley field three gas wells. The extent of neither field has been fully defined.
Gas is produced from the Huntersville chert and the underlying Oriskany sand, which are encountered at depths ranging from 4,900 to 8,250 feet. Yields vary from ½ million to 4 million cubic feet daily per well. Small flows of gas also have been obtained in the Benson and Speechley sands and Helderberg limestone in a few wells. Shows of oil have not been reported. The gas obtained in the two fields contains 97 per cent methane and 1 per cent ethane. It is consequently unlikely that oil will be found in Devonian formations. However, there are 10,000 feet or more of older Paleozoic rocks which are oil-bearing in marginal parts of the Appalachian basin. Only three of the nineteen deep wells drilled in the region have reached the base of the Silurian. Older Paleozoic formations have n t been penetrated.
It is believed that no factual or theoretical data can be presented to disprove the possibility that oil may be present in pre-Devonian formations in some of the major folds of the region where fracturing and solution weathering may have developed secondary porosity. It is possible that the hydrocarbon content of the entire pre-Trenton Paleozoic section may have migrated along fissures to the Trenton and be held there by the impermeable cover of Upper Ordovician shale.
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