| The geochemical characteristics of source rocks and its distribution are not clarified,the origins of oil and gas are not determined and hydrocarbon accumulation mechanisms are not clear.Aimed at those problems in Southwest Sub-sag,the main steps of this paper as follow: Firstly,source rocks are identified and effective source rocks are sorted out by well logging data and geochemical data.Secondly,various bio-markers and isotopes are used to determine origin of hydrocarbon.And then,analyzing hydrocarbon pools by different parameters,such as,reservoir characteristics,oil-gas distribution,potential cap rock,etc.Finally,hydrocarbon accumulation model can be built.The results indicate: source rock in the middle third member of Shahejie Formation with medium to high organic matter abundance,type II and III dominated kerogen type and middle to high mature stage are the most effective.The oil in study area originate from the third member of Shahejie Formation,the oil in Zhaozhuang-Mengju Area comes from Menggangji Subsag and the oil in Fangliji Area originates from underlying effective source rocks.Natural gas is mixing gas with oil-type and coal-type gas.the coal-type gas originates from Carboniferous-Permian System,oil-type gas comes from Shahejie Formation in Eogene System.the north natural gas is dominated by oil-type gas,while coal-type gas occupies the large part in middle study area,it is percentage of oil-type gas that seems to reduce from northeast to southwest.Finally,hydrocarbon accumulation models are built for the study area: the model in Zhaozhuang-Sangcunji Area is different step-fault zone and multi-stage hydrocarbon;the model in Mengju Area is antithetic fault seal and physical properties controls.the model in Fangliji Area is gentle step-fault zone,oil with deep burial depth and gas with shallow burial depth. |
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