Characteristic of faults and its control on hydrocarbon accumulation in Laoyemiao structural belt, Nanpu Depression

Objective The superimposed development of multistage faults is very important to the difference of hydrocarbon migration and accumulation in faulted basins. Methods Taking Laoyemiao structural belt in Nanpu Depression, Bohai Bay Basin as an example, the fault assemblage style and its origin, the relationship between fault system and oil and gas reservoir formation were studied based on geological analysis and physical simulation experiment. Results The results show that Laoyemiao structural belt developed fault combinations of "ladder" type, "domino" type, compound "y" type, compound anti "y" type. The formation of fault combinations is closely related to the boundary of the fault activity, in which "ladder" type and "domino" type fault combinations formed by the northwest-southeast and nearly north-south direction stress fields in Paleogene, while compound "y" type and anti "y" type fault combinations formed because of late superposition of fracture in Minghuazhen period. The discrete element numerical simulation results show that the existence of large plastic mudstone layers in Dongying Formation is the key material factor leading to the difference of deep and shallow deformation and vertical superposition. Conclusions Multistage fault superimposition plays an important role in controlling hydrocarbon accumulation:early faults control depressions and structural belts, late faults control traps and hydrocarbon accumulation, and fault assemblages affect hydrocarbon enrichment strata.