巻号一覧
72 巻, 4 号
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論文
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大竹 正巳, 百瀬 敦, 遠藤 晋, 兼子 高志2007 年 72 巻 4 号 p. 321-332
発行日: 2007年
公開日: 2008/11/14
ジャーナル フリーIn order to clarify the subsurface pre-Tertiary basement structure at the eastern margin of the Niigata plain, we carried out remote sensing, geological, electromagnetic and gravity surveys at Muramatsu town, Niigata Prefecture. The study area contains distinctive topographic features : a NNE-trending active reverse fault (the Muramatsu Fault) and an asymmetrical tectonic relief (the Atago hill) whose eastern margin is bounded by the Muramatsu Fault. Resistivity and gravity analyses reveal that the pre-Tertiary basement is characterized by resistive and high-density zone, and the overlying Tertiary to Quaternary sediments correspond to conductive and low-density zone. Based on the two-dimensional resistivity and density structures, a significant gap of the upper surface of the basement is inferred below the Atago hill, which is attributed to a west-dipping fault with a remarkable throw of about 1,400 m. The west-dipping fault is probably interpreted to have formed as a normal fault during rifting stage due to extensional stress. This subsurface normal fault seems to be connected to the surface active reverse fault (the Muramatsu Fault), indicating the reactivation of the former normal fault as a reverse fault under the present compressional stress. The tectonic relief of the Atago hill is likely to reflect the asymmetrical deformation of the Tertiary to Quaternary sediments due to the reactivation of the same fault.抄録全体を表示PDF形式でダウンロード (18815K) -
上田 広和, 三瓶 良和, 日浦 祐樹, 石橋 正敏2007 年 72 巻 4 号 p. 333-346
発行日: 2007年
公開日: 2008/11/14
ジャーナル フリーOil fields occur in the Sagara district of Shizuoka Prefecture, despite the disadvantageous geological conditions of a fore-arc setting. We investigated the petroleum system of this fore-arc basin in southern Shizuoka Prefecture based on hydrocarbon compositions of oils, source rock potential, organic matter type, and burial history of the Paleogene to Neogene sediments. Argillaceous rock samples from the MITI-Omaezakioki well and from outcrops in the Kakegawa and Sagara districts were analyzed for geochemical properties by CHNS elemental analyzer, Rock-Eval pyrolysis, and GC/MS.
Various maturity parameters in the Sagara oils indicate differing maturity levels, ranging up to the condensate zone. The range in maturity parameters is wider in the northwest flank of the Megami anticlinorium than in the southwest flank. The upper layers of the Lower Miocene Towata Formation and the lower layers of the Lower Miocene Matsuba Formation have relatively high potential for hydrocarbon generation (up to TOC=0.9 wt%, S2=2.8mg/g and HI=350mg/gC). The highest-potential layer of the Matsuba Formation was probably deposited in a highly productive marine environment during deposition of siliceous clastic sediments. No equivalent high-potential layers were identified in the MITI-Omaezakioki well, suggesting that the organic-rich layer formed only in the northern part of the basin. In the Eocene-Oligocene Mikura Group, layers relatively rich in TOC (up to 0.7 wt% in over-matured black shale) were observed in the Kakegawa area and also in the MITI-Omaezakioki well. According to epimerization of sterane and hopane isomers, thermal gradient was higher in the northern part of the basin than in the south. In both areas the Kurami Group only reached medium-light oil zone, whereas the Mikura Group reached the condensate zone. The thermal structure of the basin thus changed significantly between the Paleogene and Neogene.
On the basis of basin modeling simulation of the MITI-Sagara well, medium-light oils (Ro=0.7-1.0%) were generated in the Mikura Group at ca. 29 Ma and 15 Ma, and condensates (Ro=1.2%) at ca. 2 Ma. The Kurami Group generated medium-light oils (Ro=0.7-1.0%) at ca. 15 Ma and 2 Ma. Therefore, the ca. 2 Ma condensates from the Mikura Group migrated and were contaminated by oils from the Kurami Group and bitumens from the upper reservoir layers (e.g. Sagara Group).抄録全体を表示PDF形式でダウンロード (11444K) -
高部 秀樹, 植田 昌克, 大藪 健一, 伊原 賢, 坂東 克彦, 巴 保義2007 年 72 巻 4 号 p. 347-357
発行日: 2007年
公開日: 2008/11/14
ジャーナル フリーIn order to investigate corrosion behavior of representative Oil Country Tubular Goods (OCTG) materials in environments of gas condensate/water/CO2 or CO2+H2S, laboratory and field corrosion tests were carried out. The laboratory tests were carried out in CO2 or CO2+H2S environments by using an autoclave. Test specimens were set in liquid and gas phases of the autoclave and the water fraction ratio of condensate and water mixture was changed to study the effects of water fraction on corrosion behavior of OCTG materials in oil and gas well environment. In the filed tests, Down hole coupon (DHC) tests were carried out in a sour gas well in the United Arab Emirates. The DHC tests were performed at three different well depths with different water fraction. The laboratory liquid phase test results indicated that corrosion occurs by water wetting on material after emulsion break. The laboratory gas phase test results show that the vapor of condensate acts as corrosion barrier. The comparison between the laboratory and the field tests results indicates that localized corrosion occurred on carbon steel in the field test but did not occur in the laboratory gas phase test, although corrosion rate in the field test was almost the same as that in the laboratory gas phase test. This is because localized water wet condition could not be reproduced in the laboratory gas phase test. From these results, tubing material used for gas well should be selected with taking account of localized water wet conditions, even if a water fraction of bulk fluid is significantly low.抄録全体を表示PDF形式でダウンロード (8152K)
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