常磐沖堆積盆における石油システム  [in Japanese] Petroleum system in the Offshore Joban Basin, northeast Japan  [in Japanese]

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Abstract

The Offshore Joban Basin, which constitutes the southern-most part of the forearc basins located along the Pacific coast of the northeast Japan, extends about 170 km in NNE-SSW direction with 50 km width. The Upper Cretaceous and younger sediments distribute widely with maximum thickness of more than 5,000 meters. The Iwaki-oki gas field located in the Offshore Joban Basin, which is the only commercial offshore gas field in the Pacific Ocean off northeast Japan, has been producing gas since 1984. The Paleogene and Maastrichtian coals and coaly mudstones, deposited in a confined basin along continental margin, are the most likely source rocks of the gas. The basin modeling simulation in the basin depo-center west of the gas field estimates present vitrinite reflectance (Ro) values at the source rock horizon to be in the range from 1.0 to 1.3%. The simulation also indicates that maturation of the source rocks were accelerated by rapid subsidence since Miocene, and that peak gas generation and expulsion occurred during middle Pliocene. Therefore, the basin depo-center is considered as the kitchen area. Main reservoirs are the shallow marine sandstones intercalated in the Lower Miocene and the basal part of the Oligocene. The former is the producing reservoir of the Iwaki-oki gas field. Both sandstones are sealed by the extensive and thick mudstones. Primary hydrocarbon traps are NNE-SSW trending anticlines, which were formed before Middle Miocene. These anticlines are cut by NNE-SSW trending faults at their flanks. As the reservoir sandstones are about 2,000 meters vertically apart from the source rocks in the kitchen area, it is considered that expelled hydrocarbon migrated vertically through faults. Although forearc basins are not generally considered to be prospective for hydrocarbon exploration, there could be relatively good hydrocarbon system existing as shown above in the Offshore Joban Basin.

Journal

  • Journal of the Japanese Association for Petroleum Technology

    Journal of the Japanese Association for Petroleum Technology 67(1), 62-71, 2002-01

    The Japanese Association for Petroleum Technology

References:  26

Cited by:  8

Codes

  • NII Article ID (NAID)
    10008013051
  • NII NACSIS-CAT ID (NCID)
    AN00130976
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    03709868
  • NDL Article ID
    6111020
  • NDL Source Classification
    ZP29(科学技術--化学・化学工業--燃料--石油)
  • NDL Call No.
    Z17-178
  • Data Source
    CJP  CJPref  NDL  J-STAGE 
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