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The Rio Vista Gas Field is a large natural gas field in the Sacramento–San Joaquin River Delta in northern California, adjacent to Rio Vista, California. Discovered in 1936, and in continuous operation since, it has produced over of gas in its lifetime, and retains an estimated reserve of approximately .〔 p. 62.〕 In 2008 alone, the most recent year for which data was available, it produced of gas. Spanning portions of three counties and covering over , it is the largest natural gas field in California, and one of the fifteen largest in the United States.〔Rosetta Resources, California Area of Operations. (Available here )〕〔Jason Massad, "Buried Treasure: Rio Vista resource lies underground." ''The Reporter'', Vacaville, California. Retrieved August 21, 2010. Available here ().〕〔While at least one oil field in California, such as Elk Hills, currently produce more natural gas overall, Rio Vista is the largest "non-associated" gas field, i.e. it produces gas not associated with oil.〕 As of 2009, the primary operator on the field was Rosetta Resources of Houston, Texas, which owned 171 of the field's 189 active wells. The remaining 18 were run by several smaller operators, including Towne Exploration, Royale Energy, and Tri-Valley Oil & Gas.〔DOGGR (2008), pp. 149, 150, 160〕 ==Geographic setting== The gas field underlies portions of Solano, Sacramento, and Contra Costa Counties, in the bottomlands of the Sacramento – San Joaquin River Delta as well as some adjacent upland areas in the Montezuma Hills. The town of Rio Vista is entirely surrounded by the gas field, and the large 3000-home Trilogy retirement community, north of Rio Vista, is on the field's northern boundary. Additionally, the city of Isleton is on the gas field near its eastern border with the River Island Gas Field. Several state highways intersect the field, providing primary surface transportation through the area. California State Route 12 crosses the gas field from west to east, bridging the Sacramento and Mokelumne Rivers; and California State Routes 84 and 160 cross the field from north to south, with Route 160 built on levees much of the way. Much of the field underlies islands in the Delta, some of which are accessible only by ferry. Included in the gas field are Bradford Island, Twitchell Island, Brannon Island, Andrus Island, and parts of Tyler, Sherman, and Decker Islands. Most of the land area within these islands – much of which is below sea level – consists of agricultural fields protected by levees constructed in the late 19th and early 20th centuries. Drilling and maintenance pads for the gas wells are interspersed among agricultural fields, recreational areas, vacation homes, and waterways. Elevations on the gas field range from around in the Montezuma Hills southwest of Rio Vista to around ten feet below sea level in parts of the Delta islands protected by levees. Ground has been slowly subsiding in these areas for decades, due to a combination of peat decomposition, groundwater removal, and compaction of the underlying geologic structures from which trillions of cubic feet of gas have been removed.〔Steven J. Deverel, Judith Z. Drexler, Timothy Ingrum, and Christina Hart. "Simulated Holocene, Recent and Future Accretion in Channel Marsh Islands and Impounded Marshes for Subsidence Mitigation, Sacramento-San Joaquin Delta, California, USA." United States Geological Survey Water Science Center, Sacramento, California. 2008. p. 10. Available here ()〕 Climate in the area is subhumid with hot, dry summers and cool, rainy winters, with all precipitation occurring as rain. Mean annual rainfall is 14 to . Freezes occur occasionally during the winter, with the freeze-free period encompassing 250 to 275 days. Drainage on the field is poor except in the Montezuma Hills, in which it is to the south and southeast towards the Sacramento River via ephemeral streams which dry up completely in the summer. Native vegetation types include bulrushes and cattails in the wetlands and annual grasslands on the hills.〔(Montezuma Hills ecoregion description ) (U.S. Forest Service)〕〔(Delta ecoregion description ) (U.S. Forest Service)〕 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「Rio Vista Gas Field」の詳細全文を読む スポンサード リンク
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