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Tight gas is natural gas produced from reservoir rocks with such low permeability that massive hydraulic fracturing is necessary to produce the well at economic rates. Tight gas reservoirs are generally defined as having less than 0.1 millidarcy (mD) matrix permeability and less than ten percent matrix porosity.〔Ben E. Law and Charles W. Spencer, 1993, "Gas in tight reservoirs-an emerging major source of energy," ''in'' David G. Howell (ed.), ''The Future of Energy Gasses'', US Geological Survey, Professional Paper 1570, p.233-252.〕〔Ali Sharif, (Tight gas resources in Western Australia ), Western Australia Department of Mines and Petroleum, Sept. 2007.〕 Although shales have low permeability and low effective porosity, shale gas is usually considered separate from tight gas, which is contained most commonly in sandstone, but sometimes in limestone. Tight gas is considered an unconventional source of natural gas. Rock with permeabilities as little as one nanodarcy, reservoir simulation may be economically productive with optimized spacing and completion of staged fractures to maximize yield with respect to cost. ==Examples== Some examples of tight gas reservoirs are: * Muddy Sandstone/J Sandstone — Denver Basin, Colorado, USA * Mesaverde Group — Piceance Basin, Colorado, USA * Rotliegend — Germany and Netherlands〔Alan Petzet, ("Wintershall starts Dutch North Sea tight gas flow," ) ''Oil and Gas Journal'', 6 Mar. 2012.〕 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「Tight gas」の詳細全文を読む スポンサード リンク
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