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The Marcellus natural gas trend is a large and prolific area of shale gas extraction from the Marcellus Formation of Devonian age in the eastern United States. The trend encompasses 104,000 square miles and stretches across Pennsylvania and West Virginia, and into southeast Ohio and upstate New York. It is the largest source of natural gas in the United States, and production was still growing rapidly in 2013. The natural gas is trapped in low-permeability shale, and requires the well completion method of hydraulic fracturing to allow the gas to flow to the well bore. The surge in drilling activity in the Marcellus Shale since 2008 has generated both economic benefits and considerable controversy. Although before 2008 the Marcellus Shale was considered to have inconsequential natural gas potential, it is now believed to hold the largest volume of recoverable natural gas resource in the United States. In 2012, it was estimated to have 141 trillion cubic feet of technically recoverable gas by the US Energy Information Administration, and 88 trillion cubic feet by the US Geological Survey.〔US Energy Information Administration, (Annual energy outlook 2012 ).〕 In September 2012, the Marcellus Shale overtook the Haynesville Shale of northwest Louisiana as the leading producer of both shale gas and overall natural gas in the United States. In February 2014, Marcellus gas wells produced 14.0 billion cubic feet per day, a 42 percent increase over the year previous, and comprising 21 percent of all the dry gas produced that month in the United States.〔US Energy Information Administration, (Natural Gas Weekly Update ), 1 May 2014.〕 The impervious limestone layers of the Onondaga directly below the Marcellus, and the Tully Limestone at the top of the Hamilton Group, have trapped valuable natural gas reserves in this formation. The gas is produced by thermogenic decomposition of organic materials in the sediments under the high temperature and pressure generated after the formation was buried deep below the surface of the earth. The rock holds most of the gas in the pore spaces of the shale, with vertical fractures or joints providing additional storage as well as pathways for the gas to flow; gas is also adsorbed on mineral grains, and the carbon in the shale.〔 〕 ==Development history== The industry was long aware there was gas in the Marcellus, but it "occurred in 'pockets' and flows could not be sustained". These gas flows died down quickly, and the drillers soon began to ignore them when they encountered them...the consensus was that there was not enough to make a well." Before 2000, some low production gas wells were completed to the Marcellus, but these had a low rate of return, requiring a relatively long capital recovery period, although they did have a very long productive life.〔 There are wells in Tioga and Broome County, New York which are 50 years old or more. From 1976 to 1992, the U.S. Department of Energy funded the Eastern Gas Shales Project, which studied many eastern shale formations. The project drilled and cored five wells in the Marcellus in Pennsylvania. The cores established that there were enormous amounts of gas in the Marcellus, and defined fracture directions that were used in later Marcellus well drilling. Although the great volumes of trapped gas found by the project in the Marcellus and other eastern shales created excitement, the project was less successful at finding ways to recover the gas economically, especially at the low gas prices of the 1980s. "The furor over the Devonian shales faded during the early 1980s due to low gas prices and lack of sufficiently useful technologies for extracting the gas."〔 Range Resources drilled an unsuccessful well to the Oriskany Sandstone in 2003. Hoping to save some value by finding producible gas in the shallower formations in the wellbore, Range geologists noted that the Marcellus Formation had some of the same properties as the Barnett Shale of North Texas, which was a prolific source of gas. In late 2004 Range completed the well in the Marcellus, using hydraulic fracturing techniques developed for the Barnett, and started producing the well in 2005.〔John A. Harper and Jaime Kostelnik, (The Marcellus Shale play of Pennsylvania ), Pennsylvania Geological Survey.〕 Range Resources was the first company to voluntarily disclose (2010) the chemicals used at each of their fracking sites. Early experiments in Mount Pleasant Township, 30 miles southwest of Pittsburgh led to lengthy legal battles over pollution of well water and air and the industrialization of residential areas involving one of the "first sites ever drilled in the Marcellus shale" where "three of the wells... were experimental (Lavelle 2010-10-22).〔 〕 Range Resources spokesperson claimed that "more than 2,100 Marcellus wells" had been drilled in Pennsylvania by 2010 and at that time of there were "thousands of landowners across the state who have signed leases allowing gas companies to produce on or under their properties" who had not complained and "numerous happy landowners among the hundreds of Range leaseholders in Washington County" 〔 enjoying the economic benefits of leasing mineral rights on their properties. In 2013, Range allowed the two small children of the Hallowich family to talk about the Marcellus Formation.〔(【引用サイトリンク】title=Hallowich children not part of Marcellus Shale gag order agreement )〕 By 2008 the Marcellus Formation had become the focus of shale gas development, starting in Pennsylvania. Only four Marcellus wells were drilled in Pennsylvania in 2005; in 2010 1,446 Marcellus wells were drilled in Pennsylvania.〔Marcellus Shale Advisory Commission, (Final Report ), 2012, p.34.〕 Leasing agents aggressively sought out acreages to lease mineral rights. The price for leasing rose from $US300 per acre in February to $2,100 in April, 2008.〔 〕 In July 2010, the U.S. Department of Labor announced a $5 million grant to train workers for Marcellus shale drilling.〔("Marcellus workforce training" ), WDUQ. 2 July 2010. Retrieved 13 July 2010.〕 To extract the shale gas at more commercially viable rates,〔 directional drilling is done to depths of underground to reach the formation, and then water and a mixture of chemicals is pumped into the rock under high pressure in a process known as hydraulic fracturing to release the gas from the low permeability shale. Several companies have carried their experience tapping the Barnett Shale of Texas into the Marcellus trend. The Marcellus covers several times more area,〔 stretching , compared to a linear extent of only for the Barnett. As of 2008, only a few new Marcellus wells were actually in operation, with at least one reported to be producing more than 3 million cubic feet (85 thousand m³) per day.〔 Engelder, who has studied natural rock fractures in this area for more than 25 years, noted that drilling horizontally through the Marcellus shale perpendicular to the vertical fractures better connected the natural pathways for gas flow.〔 Early results show that horizontal wells in this formation are producing gas at a rate more than double that of vertical wells, and at slightly lower cost overall,〔 despite the much higher initial cost of drilling.〔 Since parts of this region have been producing gas from wells drilled to the deeper Oriskany Formation sandstone, older wells that are no longer viable can be reused, either by fracturing the Marcellus layer in the existing well bore, or by refinishing the bore using horizontal drilling into the Marcellus.〔 Re-use of the existing infrastructure has both environmental as well as economic benefits,〔 because in addition to avoiding development of new drilling sites and wells, existing transportation facilities can be reused. Researchers at the University of Pittsburgh recently released a study showing that "7 percent of Allegheny County's land has been leased for drilling and extraction since 2003" and the number of properties in the county leased for oil and gas exploration has grown exponentially in recent years. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Marcellus natural gas trend」の詳細全文を読む スポンサード リンク
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