Zou Caineng; Xu Chunchun; Wang Zecheng; Hu Suyun; Yang Guang; Li Jun; Yang Wei and Yang Yu
, 2011, 38(6): 1985-0.
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The large gas province of platform margin reefs and shoals of the Permian Changxing Formation and Triassic Feixianguan Formation in the Sichuan Basin are studied to describe the forming conditions and geological characteristics of large strip-like gas provinces of platform margin reefs and shoals. The Sichuan Basin experienced cratonic rifting and basement faulting during the Late Permian. Within a widespread regional ramp, a paleogeomorphology pattern of “three highs and three depressions” were formed. The three negative relieves are, respectively, Chengkou-E’xi trough, Kaijiang-Liangping trough, and Nanchong-Mianyang intraplatform depression, and the three topographic highs are Fengjie-Zhenba platform flat, Shizhu-Yilong platform flat, and Suining-Moxi platform flat. In the transitional areas between platform flats and troughs, large-scale platform margin reef-shoal complexes were developed under high energy environment. Diagenetic processes, such as early stage solution, seepage-reflux dolomitization and burial solution, contributed to high-quality dolomite reservoirs along platform margins. High mature source rocks and faults were developed within the platform margin reef-shoal complexes, forming better hydrocarbon accumunation conditions than intraplatform reefs and shoals. Therefore, the distribution of platform margins controlled that of gas accumulation zones. Paleogeography background of large platform, extensive dolomitization and solution in reef-shoal reservoirs, advantageous underlying and lateral adjacent source rocks, strip assemblages of lithological, structural, and litho-structural oil and gas traps are the four basic elements that determine the formation and distribution of large strip gas provinces. The configuration of the four elements in the studied area shows promising exploration prospects of large platform margin oil and gas provinces.