Research on history of gas migration and accumulation in fault basin: Taking Wen 23 Gas Field of Dongpu Depression as an example

The history of gas migration and accumulation includes the origin,migration pathways,charging process,charging history of natural gas and the matching relations of the main factors for hydrocarbon accumulation.Taking Wen23 Gas Field in Dongpu Depression as a case,the dynamic processes of hydrocarbon generation,migration,accumulation and preservation of natural gas were discussed based on the comprehensive research of petroleum geology and test data.The natural gas in this area is mainly from the coal-source rocks of the Permo-Carboniferous system in Qianliyuan sub-depression.The coal-formed gas migrated along the Wendong fault firstly to the sandstone in the fourth member of Shahejie Formation and then along the high-porosity and high-permeability zone of sand body towards the northwest.The coal-formed gas continuously accumulated in the favorable place of the fourth member of Shahejie Formation reservoir in the period from the first member of Shahejie Formation depositional stage to the late of Dongying Formation.The original gas-water interface is about 10 m lower than that of gas reservoirs at present,which indicates that natural gas in the fourth member of Shahejie Formation reservoir of Wen23 Gas Field dissipated in the last stage of the Dongying movement to some extent.