/Image1482.gif) 図 4-2-1 世界の油・ガス田地帯 出所：石油・天然ガス開発資料（石油鉱業連盟・ＪＯＧＭＥＣ） JX日鉱日石エネルギー（HP/2015/2）による『石油便覧』の『第4編 第2章 第1節 原油生産地域と主要油・ガス田』から |
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最終更新日：2016年11月25日
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石油（Oil：原油、Crude Oil）は地下（Underground）に胚胎している。濃集しているために経済的に利用できる場所を石油鉱床（Petroleum Deposit）と呼ぶが、一般的には油田（Oil
Field）と呼ばれることが多い。過去の生物体（Ancient Biomass）が地下の高温・高圧条件下で有機化学反応（Organic Cheical Reaction）と移動（Migration）を行って、トラップ〔Trap：罠を意味する：根源岩（Source
Rock）と貯留岩（Reservoir
Rock）と帽岩（Cap
Rock）の3つの働きをするものが必要〕と呼ばれる条件が整った場所にのみ形成される。石油は非常に多種類の有機化合物（Organic Compond：炭化水素、Hydrocarbons）の混合物であるが、温度がある程度高くなるとメタン（Methane、CH4）に変わってしまう。メタンは天然ガス（Natural Gas）の主成分である。つまり、石油は天然ガスを伴うことが普通であるので、ガス田〔Natural Gas Field：天然ガス鉱床（Natural
Gas Deposit）〕も油田に伴うことが多い。地下で、これらは岩石（Rock）を構成する鉱物（Mineral）粒子間の孔隙（Pore）に存在するが、密度（Density）の違いによって、下側から水（地下水、Groundwater）、石油、天然ガスの順番に層状に賦存している。 なお、世界最大の油田は、サウジアラビア（Saudi Arabia）のガワール油田（Ghawar Oil Field）である。 |
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図 4-2-1 世界の油・ガス田地帯 出所：石油・天然ガス開発資料（石油鉱業連盟・ＪＯＧＭＥＣ） JX日鉱日石エネルギー（HP/2015/2）による『石油便覧』の『第4編 第2章 第1節 原油生産地域と主要油・ガス田』から |
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〔外務省の『外交政策』の『経済』の『エネルギー』の『エネルギー基礎統計』の『付属資料（世界の主要油田・ガス田（一覧、地図））』から〕 |
| 日本 |
/Image2202.gif) シェールオイル開発予定地 朝日新聞による『日本初、秋田に「シェールオイル」 来年にも試験生産へ』（2012/7）から 秋田県由利本荘市の鮎川油ガス田周辺（地下約1800メートル）。石油資源開発（株）が開発予定。石油埋蔵量は500万バレル程度。 |
/Image433.gif) わが国の油ガス田（2008年1月末現在） 1 勇払油・ガス田、2 申川油田、3 八橋油田、4 鮎川/由利原油・ガス田、5 余目油田、6 岩船沖油・ガス田、7 中条/紫雲寺油・ガス田、8 東新潟ガス田/南阿賀油田、 9 吉井/東柏崎ガス田、10 見附油田/雲出ガス田、11 南長岡/片貝ガス田、12 頸城油・ガス田、13 磐城沖ガス田、14 南関東ガス田（茂原、合同千葉ほか） /Image434.gif) 注：※は水溶性天然ガス 出所：天然ガス鉱業会 「わが国の石油・天然ガスノート」2008.1版 石油鉱業連盟（HP/2011/5）による『わが国の油ガス田』から 2008年度の自給率は、原油0.4％、天然ガス3.8％、原油＋天然ガス1.4％であった。 |
 ■操業中の主な石油・天然ガス田 （２００５年７月末現在） 〔JOGMEC NewsのVol.3 2006年1月号の中の『日本国内の油・ガス田』から〕 |
| 中東の油田 |
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Upper Jurassic Petroleum System of the Arabian basin During the Late Jurassic, sea level appears to have risen steadily, as evidenced by the continued recession of the continental margin. On the platform, however, carbonate deposition kept pace with and finally superseded the flooding, reestablishing very shallow depositional conditions over the southern part of the Middle East (Murris, 1980). Oil Discovery The Saudi Arabian government signed the first concession on May 29, 1933 which gave Standard Oil of California (Socal) exclusive rights to prospect for and produce oil in the eastern regions of Saudi Arabia (Nawwab et al., 1980). This agreement was to run for a period of sixty-six years. Exploration and drilling commence shortly after; and on April 30, 1935 California Arabian Standard Oil Company (Casoc, a new subsidiary of Socal) began drilling the first oil well (Dammam Well No. 1), which was a disappointment since very little oil actually was found at a shallow depth. Ghawar's primary producing structures are, from north to south: Ain Dar, Shedgum, Uthmaniyah, Farzan, Ghawar, Al Udayliyah, Hawiyah, and Haradh . The Ghawar filed accounts for about half of Saudi Arabia's total oil production capacity. The range of crude Saudi Arabia produces ranges from heavy to super light (API 27 o -50 o) (table 6.1). Of Saudi Arabia's total oil production capacity, about 65%-70% is considered light gravity, with the rest either medium or heavy. The lightest grades generally are produced onshore, while the medium and heavy grades come mainly from offshore. The Ghawar field is the main producer of 34o API Arabian Light crude, while Abqaiq produces 37o API Arab Extra Light crude. Since 1994, the Hawtah Trend of Central Saudi Arabia, which includes the Hawtah field and smaller satellites (Nuayyim, Hazmiyah) south of Riyadh, has been producing around 200,000 bbl/d of 45o-50o API, 0.06% sulphur, Arab Super Light. Offshore production includes Arab Medium crude from the Zuluf (over 500,000 bbl/d capacity) and Marjan (270,000 bbl/d capacity) fields and Arab Heavy crude from the Safaniya field (EIA, 2002). |
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Petroleum System This section provides a brief overview of the source-reservoir-seal triplet of the late Middle to the Upper Jurassic of the Arabian Basin. Hanifa sequence stratigraphy section provided more detail of the sequence stratigraphic analysis of the Hanifa Formation source and reservoir. Please refer to for formation nomenclature and lithology. Source Rocks The Tuwaiq Mountain Formation and Hanifa Formation of the Jurassic Callovian-Oxfordian are believed to be the primary source for the overlying prolific hydrocarbons accumulations of the Upper Jurassic Arab Formations. The Tuwaiq Mountain source rock is dominant in the southwest while the Hanifa source rocks are present in the northwestern region of the Arabian Basin. Carrigan et al. (1995) also determined that the oils in the Arab and Hanifa reservoirs have similar bulk compositional, isotopic, chromatographic, and biomarker signatures and matched the overall Hanifa and Tuwaiq Mountain source rock extract characteristics. The primary facies of these rocks are thinly (0.5-3 mm thin) laminated lime-mudstone with total organic contents (TOC) averaging between 3-5%(Murris, 1980). These source facies are interpreted to have deposited in a restricted, partly anoxic intrashelf basin separated by carbonate grainstone and dolomitized facies from the open-marine environment of the Neo-Tethys Sea to the east (Ayres et al., 1982). According to Ayres (1982), these source rocks have a distinct wireline log character due to the high organic content (high resistively and low sonic velocity) with low porosity (2-6% porosity). The high organic productivity may be attributed to climatic and oceanographic conditions. There was oceanic upwelling at the margin of the Neo-Tethys with its prevailing southeasterly trade winds (Stoneley, 1990). Reservoirs The Upper Jurassic reservoirs consist mainly of limestone. Most of the reservoirs are formed of carbonates with keep-up sheet-like geometry deposited during a steady rise in sea level of the transgressive systems tract in the early Upper Jurassic. These reservoirs became increasingly regressive and contain shallower facies toward the top of the Jurassic and were culminated by the deposition of the regional Hith evaporite seal. Following is a brief description of the reservoir units starting with the Tuwaiq Mountain and ending with the Hith Formation. |
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| SEPM STRATA（2013/10）による『Arabian Basin Petroleum』から | |
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A Brief Tectonic History of the Arabian basin The vast hydrocarbon accumulations of the basin. Basins of the Upper Jurassic are directly tied to the tectonic evolution of the Arabian Plate. This section attempts to trace the development of the northeast margin of the Arabian Plate a development accumulation the vast accumulation of the source, reservoir, and seal rocks of the Upper Jurassic and to the migration and trapping of these vast hydrocarbon reserves. The Arabian Plate tectonic history can be subdivided into six tectonic phases that shaped its geology. These include: ・Pre-Cambrian ・Ordovician-Silurian Glaciation / de-Glaciation ・Carboniferous (Hercynian Orogeny) ・Early Triassic (Zagros Rifting) ・Late Cretaceous (First or Early Alpine Orogeny) ・Tertiary (Second or Late Alpine Orogeny) ・Neogene Separation from Africa. The geological map of the Arabian Plate illustrates that divergent margins are forming in the spreading centers of Red Sea and Gulf of Aden to the west and southwest of the Arabian Plate. The South and southeast of the Arabian plate is bounded by the Owen-Sheba intra-oceanic transform fault. An active convergent margin lies to the north and northeast with Turkey (Bitlis sutures) and east within Iran (Zagros Mountains) where the Arabian plate is thrusting beneath the Eurasian plate. The Dead Sea represents a transform strike-slip fault zone to the northwest of the Arabian Plate. |
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Late Permian through the Jurassic Zagros Rifting In the Late Permian, the Arabian-Gondwana/Iranian-Laurasia super continent was fragmented when the crust was stretched, and by the Early Triassic eventually rifted along the Zagros line to form the Neo-Tethys Sea (eastern margin of the Arabian Plate) (Beydoun, 1991). During the Jurassic the Arabian plate was relatively tectonically stable and was located at the Equator enabling the development of a wide shallow shelf on the western passive margin of the Neo-Tethys on which carbonates accumulated over the shelf and inner platform. Most of the Arabian Gulf petroleum source-reservoir-seals accumulated during the Jurassic and Cretaceous. |
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The climate became more humid towards the end of Early Jurassic.
As a result, evaporites deposition was rare. Intrashelf depressions
such as the Gotnia, the South Rub' AlKhali, and the Arabian Basins
were created as a result of tectonic differentiation and rising
sea level. The major formation of the Arabian platform was initiated in the Late Callovian, and caused the deposition of the organic rich rocks that form the major source formation in the anoxic intrashelf basins of the Middle East (e.g., Gotnia Basin and Arabian Basin). The carbonate deposition on the shelf kept pace with changes in sea level until the end of Jurassic when the major evaporitic seals were deposited during a fall in sea level as the climate became predominantly arid. |
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| SEPM STRATA（2013/2）による『Arabian Basin Tectonics』から | |
/Image1476.gif) Ten countries in the Middle East account for only 3.4% of the area but contain 48% of world’s known oil reserves and 38% of natural gas reserves. Despite decades of exploration worldwide, we have not found ‘another Middle East.’ Source: Rasoul Sorkhabi |
/Image1477.gif) The tectonic framework of the Middle East is divided into (1) Zagros fold-and-thrust belt, (2) Unstable Arabian shelf, and (3) Stable Arabian shelf. The Arabian continental plate, which collided with the Asian plate along the Bitlis-Zagros suture during the Eocene, is still converging with Asia at a rate of 1.9 to 2.3 cm per year based on GPS measurements. (Global measurements of relative plate motions of Arabia with respect to Eurasia show higher velocities of 2.4-3.5 cm per year). This continental collision gave rise to the Zagros orogen and its Cenozoic foreland basin, which was superimposed on the Paleozoic-Mesozoic Tethys shelf basin. The cumulative thickness of sediments in the region reaches up to 12 km. The Zagros deformation and salt domes have folded the sedimentary beds into large, gentle anticlines (‘whaleback’ structural traps). The western and southern boundaries of the Arabian plate are bounded respectively by the Red Sea and Gulf of Aden rifts. These Neogene continental rifts have separated Arabia from Africa, and are further pushing Arabia against Asia. The rift-shoulder uplifts have outcropped the Precambrian rocks (part of the Nubian-Arabian shield) along the Red Sea and are capped at places by rift-related volcanic rocks. |
/Image1478.gif) Movement of the Kuwait-Persian Gulf area throughout Phanerozoic times. Also shown are major geologic events relevant for sedimentation history of the region. Compiled from various sources including Beydoun (Episodes, June 1998). |
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/Image1479.gif) World paleogeography in the Early Jurassic (～200 Ma) when the Middle East was part of Gondwana passive margin and was submerged under the warm equatorial waters of Neo-Tethys. The triangular Neo-Tethys Ocean had a wide and long shelf, restricted on the western end but open to the east. The idea of trade winds and Neo-Tethys ocean currents (concentrating nutrients for planktons) comes from Irving et al. (Canadian Journal of Earth Science, Jan. 1974). These conditions, which favoured the eposition of organic-rich source rocks and thick carbonates, prevailed in the Middle East until the latest Cretaceous. |
/Image1480.gif) Stratigraphy and petroleum source-reservoir rocks of selected areas in the Middle East. Data compiled mainly from Beydoun (1999) and Alsharhan & Nairn (2003). Illustration by Rasoul Sorkhabi |
| Sorkhabi（2010）による『Why So Much Oil in the Middle East?』から | |
/Image1493.gif) Figure 2. Arabian Peninsula during Early Permian showing area of erosion or nondeposition (blue dashed lines), known Unayzah dune fields (yellow area), probable glacial lake (blue area), and dominant wind direction (arrow) across central eroded portion of Arabian Peninsula. Modified from Heine (in press). Al-Anazi（2007/4）による『What you know about The Ghawar Oil Field, Saudi Arabia?』から |
/Image1499.gif) Figure 1. Generalized Late Jurassic stratigraphy and lithologies in Saudi Arabia, with Arab and Hith reservoirs named. Modified from Powers (1968)and Meyer et al. (1996). |
/Image1487.gif) Figure 2. Generalized geologic map of the Arabian Peninsula and the position of the central Arabian arch. Modified from Al-Hinai et al.(1997) and U.S. GeologicalSurvey (1963). |
/Image1498.gif) Figure 5. Late Jurassic paleogeography of the Arabian Peninsula and surrounding area. Average directions of Arab-D and Jubaila progradation are shown by arrows. Blue band west of Riyadh is the Tuwaiq escarpment. Modified from Handford et al.(2002), Al-Husseini(1997), Ayresetal.(1982) ,R.B.Koepnick and L.E.Waite(1991,personalcommunication), Murris (1980), and Scotese (1998). |
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| Lindsay et al.（2006）による『Ghawar Arab-D Reservoir:Widespread Porosity inShoaling-upward CarbonateCycles, Saudi Arabia』から | |
/Image1496.gif) Figure 2 Conceptional sketch of the Arabian plate ("Arabian Promontory") from Jurassic to Eocene showing the principal plate boundaries then with new Neogene plate boundaries added and also indicating the width of the NE Arabian shelf then and now and principal tectonic features (modified with permission from M. W. Hughes Clarke, unpublished). |
/Image1495.gif) Figure 3 Stratigraphical position of the identified source rocks in the NE Arabian shelf region and Oman(expanded and modified from Stoneley, 1990 and Beydoun, 1993). |
/Image1494.gif) Figure 5 Generalized paleolatitude curve for the Kuwait/Basra area (Head of the Persian/Arabian Gulf) during the Phaneroroic (area positions based on Scotese and Golonka, 1992). |
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| Beydoun（1998/6）による『Arabian plate oil and gas: Why so rich and so prolific?』から | |
| 北海油田 |
/Image1850.gif) Location of the Brent oil platform in the North Sea Wikipedia（HP/2015/3）による『Brent Crude』から |
/Image1848.gif) The Exclusive Economic Zones in the North Sea Wikipedia（HP/2015/3）による『North Sea oil』から |
/Image1846.gif) 北海油田と国境 |
/Image1847.gif) 北海油ガス田分布図、緑が油田、赤がガス田 |
| ウィキペディア（HP/2015/3）による『北海油田』から | |
/Image1843.gif) Acorn Petroleum Services（HP/2015/3）による『Northern/Central North Sea Map』から |
/Image1831.gif) North Sea portfolio |
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| BP（HP/2015/3）による『North Sea portfolio』から | |
/Image1844.gif) Key North Sea oil and natural gas fields and terminals Source: U.S. Energy Information Administration, United Kingdom Department of Energy and Climate Change, Norwegian Petroleum Directorate USEIA（2013/8）によるToday in Energyの『Summer maintenance affects North Sea crude oil production and prices』から |
/Image1845.gif) North Sea Petroleum The dark blue curve equals the sum of the three Hubbert cycles. 1) is best viewed as surge production from the Forties, Brent, Piper and Ninian Fields when they came on stream in the early 1980s, 2) represents the main discovery and field development cycle of the North Sea, 3) represents a late discovery cycle, Ormen Lange in 1997 and Buzzard in 2001. Both fields came on stream in 2007. Mearns（2009/10）による『North Sea Petroleum Reserves』から |
