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Ekofisk is an oil field in block 2/4 of the Norwegian sector of the North Sea about southwest of Stavanger. Discovered in 1969 by Phillips Petroleum Company,〔(【引用サイトリンク】title=The NPD's Fact-pages – EKOFISK] )〕 it remains one of the most important oil fields in the North Sea. This was the first discovery of oil after the drilling of over 200 exploration wells in the North Sea "triggered" by the Groningen gas field discovery.〔Van den Bark, E., and Thomas, O.D., 1980, Ekofisk: First of the Giant Oil Fields in Western Europe, in Giant Oil and Gas Fields of the Decade: 1968-1978, AAPG Memoir 30, Tulsa, American Association of Petroleum Geologists, pp. 195-197〕 In 1971, Phillips started producing directly to tankers from four subsea wells.〔 〕 Oil production is planned to continue until at least 2050.〔http://www.conocophillips.no/EN/Norwegian%20shelf/Ekofisk/EkoEko/Pages/index.aspx〕 Ekofisk reservoir consists of Cod, Ekofisk, West Ekofisk, Tor, Albuskjell, Eldfisk, Edda and Embla oil fields. The Ekofisk Center is a vast complex of platforms and structures creating a transportation hub also for surrounding fields such as Valhall, Hod, Gyda, Ula, Statfjord, Heimdal, Tommeliten and Gullfaks. The whole complex consists of 29 platforms.〔 Produced oil is transported by the Norpipe oil pipeline to the Teesside Refinery in England.〔 〕 Natural gas is transported by the Norpipe gas pipeline to Emden in Germany.〔 〕 ==Geology== The Ekofisk field is a central graben, north-south trending anticline in area, with of vertical closure and a hydrocarbon column long, formed by Permian Zechstein salt movement in the form of salt pillows.〔Van den Bark, E., and Thomas, O.D., 1980, Ekofisk: First of the Giant Oil Fields in Western Europe, in Giant Oil and Gas Fields of the Decade: 1968-1978, AAPG Memoir 30, Tulsa, American Association of Petroleum Geologists, p. 211〕 The production zones at a depth of about 3 km, include the Paleocene Ekofisk Formation and the Upper Cretaceous Tor Formation, both Chalk Group rocks containing porosities of 30-40%.〔Van den Bark, E., and Thomas, O.D., 1980, Ekofisk: First of the Giant Oil Fields in Western Europe, in Giant Oil and Gas Fields of the Decade: 1968-1978, AAPG Memoir 30, Tulsa, American Association of Petroleum Geologists, pp. 195, 208 and 200〕 "The reservoir rock...is a true chalk-a fine-grained limestone composed of the skeletal remains of pelagic unicellular golden-brown algae or coccolithophores".〔Van den Bark, E., and Thomas, O.D., 1980, Ekofisk: First of the Giant Oil Fields in Western Europe, in Giant Oil and Gas Fields of the Decade: 1968-1978, AAPG Memoir 30, Tulsa, American Association of Petroleum Geologists, p. 200〕 The source rocks are the Upper Jurassic Kimmeridgian shales.〔Van den Bark, E., and Thomas, O.D., 1980, Ekofisk: First of the Giant Oil Fields in Western Europe, in Giant Oil and Gas Fields of the Decade: 1968-1978, AAPG Memoir 30, Tulsa, American Association of Petroleum Geologists, pp. 211-213〕 The structure was discovered using reflection seismology in the 1960s, although the initial interpretations were distorted due to high-pressure zones in the overlying tertiary rocks causing low seismic velocities.〔 However, the high porosity of the reservoir rock does cause an increase in seismic amplitude which can be used with an isopach map to determine net pay.〔 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「Ekofisk oil field」の詳細全文を読む スポンサード リンク
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