Analysis of Dominant Migration Pathway: A Case Study on Neogene in Eastern Bohai

The hydrocarbon accumulation of Neogene in eastern Bohai Sea is closely related with fault transportation, and the dominant migration pathway controlled by the migrating fault is a key to the favorable accumulation zone and block with high hydrocarbon abundance. Based on three-dimensional seismic, drilled wells and logging data, the authors conducted the identification of main migrating faults, classified the internal structural units of the faults and the configuration between fault plane and strata, studied the dominant migration pathway based on the sealing capacity and the configuration between fault plane and strata. It indicates that the major faults which contact the source rocks with greater area and strongly activated in late period acted as the main migrating faults, and the fault zone is a geological complex consisting of the broken zones in the central and induced fracture zones on both sides. With the integrated consideration of lithology configuration, occurrence configuration, shale smear, fault property and fault plane stress, a fuzzy evaluation of the lateral sealing of the main faults in Neogene was conducted. It shows that Bodong low uplift, Miaoxibei uplift and the gentle slope on the eastern flank of Bodong sag are the favorable zones for hydrocarbon accumulation. Furthermore, some blocks with high hydrocarbon abundance were predicted by detailed description of fault plane morphology and strata occurrence, and are confirmed by drilling activities. This study on the prediction of preferential reservoir forming zone and exploration block with high abundance provides a reference to the exploration elsewhere.