The Marcellus Shale is a rock formation that underlies approximately two-thirds of Pennsylvania and portions of the states of New York and West Virginia at a depth of 5,000 to 8,000 feet and is believed to hold trillions of cubic feet of natural gas and has long been considered prohibitively expensive to access. Recent advances in drilling technology and rising natural gas prices have attracted new interest in this previously untapped formation. The geology of the Marcellus formation suggests that areas in the southwest, northcentral and northeastern regions of Pennsylvania that have not traditionally seen much gas well drilling may be especially productive.
Natural Gas Extraction from the Marcellus Shale
Extracting natural gas from the Marcellus Shale formation requires both vertical and horizontal drilling, combined with a process known as "hydraulic fracturing". After the well is drilled, cased and cemented to protect groundwater and the escape of natural gas and other fluids, drillers pump large amounts of water mixed with sand and other fluids into the shale formation under high pressure to fracture the shale around the well, which allows the natural gas to flow freely to the well bore. The amount of water typically required for hydraulic fracturing ranges from about one million gallons for a vertical well to approximately five million gallons for a vertical well with a horizontal lateral.
