Physical modeling of petroleum downward migration：A case study of western Chezhen Sag, Jiyang Depression, Bohai Bay Basin

According to the theory of hydrocarbon downward migration, based on seismology, geochemistry, well drilling and logging, it is discussed in this paper the accumulation mechanism of petroleum downward migration in the western Chezhen Sag, the Jiyang Depression, the Bohai Bay Basin. The main pathways of hydrocarbon downward migration include factures or micro cracks in the process of secondary migration, and the formation process of hydrocarbon downward migration is reproduced by experimental simulation. Source rocks in the middle and lower subsections of the 3rd member of the Shahejie Formation have good genetic relationships with oil sands from the upper subsection of the 4th member of the Shahejie Formation, and reservoirs discovered in the upper subsection of the 4th member of the Shahejie Formation are buried deeper than the bottom boundary of source rocks from the 3rd member of the Shahejie Formation. In the lower subsection of the 3rd member of the Shahejie Formation, pressure coefficients range from 1.0 to 1.4, and decrease both upwards and downwards, providing force for petroleum downward migration. Cracks and fractures break the mudstone interlayers between the bottom boundary of source rocks from the 3rd member of the Shahejie Formation and the top surface of the 4th member of the Shahejie Formation. As a result, source rocks and reservoirs are connected.