Oil & Gas Geology ›› 2005, Vol. 26 ›› Issue (2): 208-213.doi: 10.11743/ogg20050212

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Chronological characteristics of Upper Triassic reservoirs in western Sichuan depression

Yang Keming1,2, Ye Jun2, Lü Zhengxiang1,2   

  1. 1. Energy College, Chengdu University of Technology, Chengdu, Sichuan;
    2. Southwest Branch Company, SINOPEC, Chengdu, Sichuan
  • Received:2005-02-28 Online:2005-04-25 Published:2012-01-16

Abstract:

The Upper Triassic in western Sichuan depression can be divided into 2 source-reservoir-cap rock combinations. The peak of hydrocarbon generation and expulsion in the lower combination occurred during middle-late stages of Late Triassic; while that in the upper combination occurred in Late Jurassic. Both mechanical compaction and infilling of authigenic minerals would have contributed to the tightening of reservoirs in Xujiahe Fm, which occurred at the end of the Middle Jurassic Upper Shaximiao through to Late Cretaceous. Analysis of fluid inclusions indicates that gas reservoirs in the 2nd member of Xujiahe Fm were charged mainly at the end of the deposition of the 4th member of Xujiahe Fm through to the end of Middle Jurassic. Multiple phases of tectonic movements resulted in polyphase traps in western Sichuan depression, of which the large Yanshanian palaeohigh had the best timing with hydrocarbon migration and accumulation. Based on the stages of hydrocarbon generation and expulsion, tightening of reservoirs, fluid charging and trap formation, it can be determined that the main reservoiring stage in the Upper Triassic in western Sichuan depression would be from middle-late Indosinian to middle-late Yanshanian.

Key words: western Sichuan, Upper Triassic, tightening, trap, hydrocarbon charging, reservoiring period

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