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The Piceance Basin is a geologic structural basin in northwestern Colorado, in the United States. It includes geologic formations from Cambrian to Holocene in age, but the thickest section is made up of rocks from the Cretaceous Period. The basin contains reserves of coal, natural gas, and oil shale. ==Natural gas== The basin has come to increasing public attention in recent years because of widespread drilling to extract natural gas. The primary target of gas development has been the Williams Fork Formation of the Mesaverde Group, of Cretaceous age. The Williams Fork is a several-thousand-foot thick section of shale, sandstone and coal deposited in a coastal plain environment. The formation has long been known to contain natural gas. The sandstone reservoirs have low permeability and limited areal extent, however, which made gas wells uneconomic in the past. In 1969 an atomic device was detonated in a well drilled into the Williams Fork Formation southwest of Rifle, Colorado in an attempt to fracture the rock and enable commercial extraction of natural gas. Project Rulison, as it was called, was a failure. Advances in hydraulic fracturing within the past decade, along with higher gas prices, have made gas wells broadly economic in the area. In 2007 the basin contained five of the top 50 US gas fields in proved reserves (Grand Valley #16, Parachute #24, Mamm Creek #27, Rulison #29, and Piceance Creek #46).〔(US Energy Information Administration: ''Top 100 oil and gas fields'' ), Table B2, PDF file, retrieved 19 February 2009.〕 Increased gas drilling in recent years has been criticized by some. There is strong criticism of drilling for gas in previously undeveloped areas such as the Roan Plateau. 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「Piceance Basin」の詳細全文を読む スポンサード リンク
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