Since the mid nineteenth century, over 500,000 wells have been drilled in the Appalachian Basin. While many of these wells have been plugged and abandoned, approximately 185,000 wells are still active producers. A majority of these active wells were drilled during the last ten years at depths averaging approximately 3,200 ft [975.4 m]. The recent decrease in oil and gas prices has made it increasingly difficult for producers to Justify new shallow drilling programs. There are, however, deeper productive horizons in many existing wells that have remained untapped. A number of unique procedures have been developed which allows the deepening, economically, of existing wells through existing casing as small as 4-1/2 in [114 mm].

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