Citation: | SUN Yanze, LI Shizhen, LIU Weibin, LIU Yan, KE Changwei, XU Yaohui. Hydrocarbon generation potential and gas genesis of Cretaceous source rocks in Hesigewula Sag, western margin of Great Khingan[J]. Geological Bulletin of China, 2021, 40(9): 1484-1492. |
The Hesigewula Sag on the western margin of the Great Khingan is a newly-discovered sag where the hydrocarbon generation potential of its potential source rocks has not been systematically studied.Based on the analysis of organic petrology and organic geochemistry of 160 core samples from three parameter wells and some coalfield exploration wells in the Hesigewula Sag, and combined with tectonic and sedimentary characteristics, the hydrocarbon generation potential of Cretaceous mudstone in the Hesigewula Sag is systematically analyzed.The genetic types of natural gas in Well Hedi 1 are also discussed.The total organic carbon of Lower Cretaceous dark mudstone in Hesigewula Sag is high.The average TOC of K1bt1mudstone is 2.20% and the K1bt2 is 3.67%.The type of the organic matter is Ⅱ1-Ⅱ2.The degree of thermal evolution is relatively low, and it is at the stage of immature-low maturity.The carbon isotope of methane in Well Hedi 1 is relatively light, with contents ranging from -70.5‰ to -68.2‰.Combined with the hydrogen isotope characteristics of methane, it is considered that the natural gas in Well Hedi 1 is biogenic gas, which is produced by the mixture of carbon dioxide reduction and acetic acid fermentation.Because the core samples are generally collected less than 1000 meters at depth, it is presumed that the deep part of the depression(more than 2000 meters) has entered the peak period of oil generation, which has a certain exploration potential.
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Structural units of the Hesigewula area in Erlian Basin
Thickness of argillaceous source rocks in K1bt1(a)and K1bt2(b)in Hesigwula Sag
Contrast diagrams of hydrocarbon source rocks of the Tengger Formation in Hedi 1, Hedi 2 and Mengwucan 1 wells
Histogram of total organic carbon(a) and hydrocarbon generation potential(b)
Relation between TOC and HI of source rocks in the in K1bt1(a)and K1bt2(b)
Classification of HI and Tmax in K1bt1and K1bt2
Van's diagram of the classification types of organic elements in kerogen
Histogram of Tmax in K1bt1and K1bt2
Relationships between Tmax and Ro with depth
Natural evolution profile of sterane isomerization parameters in source rocks of well Hedi 2
Identification of natural gas genesis in well Hedi 1