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Li J.,Petrochina | Li J.,Key Laboratory of Natural Gas Reservoir Formation and Development | Wang Y.,Petrochina | Wang Y.,Key Laboratory of Natural Gas Reservoir Formation and Development | And 8 more authors.
Natural Gas Industry | Year: 2015

Oil-cracked gas, as the main type of high-over mature marine natural gas in China, is mainly derived from occluded hydrocarbon. So it is significant to carry out quantitative study on occluded hydrocarbon. In this paper, the occluded hydrocarbon volume of the main basins in China was calculated depending on their types, abundances and evolution stages by means of the forward method (experimental simulation) and the inversion method (geologic profile dissection). And then, occluded hydrocarbon evolution models were established for five types of source rocks (sapropelic, sapropelic prone hybrid, humic prone hybrid, humic and coal). It is shown that the hydrocarbon expulsion efficiency of sapropelic and sapropelic prone hybrid excellent source rocks is lower than 20% at low-maturity stage, 20%-50% at the principal oil generation stage, and 50%-80% at high-maturity stage, which are all about 10% higher than that of humic prone hybrid and humic source rocks at the corresponding stages. The resource distribution and cracked gas expulsion of occluded hydrocarbon since high maturity stage of marine source rocks in the Sichuan Basin were preliminarily calculated on the basis of the evolution models. The cracked gas expulsion is 230.4×1012 m3 at the high evolution stage of occluded hydrocarbon of Qiongzhusi Formation, Lower Cambrian in this basin, and 12.3×1012 m3 from the source rocks of Doushantuo Formation, Sinian, presenting good potential of natural gas reservoir accumulation. It is indicated that the favorable areas of occluded hydrocarbon cracked gas in Qiongzhusi Formation source rocks in the Sichuan Basin include Gaoshiti-Moxi, Ziyang and Weiyuan, covering a favorable area of 4.3×104 km2. © 2015, Natural Gas Industry Journal Agency. All right reserved. Source

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