Coupling Characteristics between Episodic Hydrocarbon Expulsion and Fault Throw Increase for Middle-Shallow Formations in Songliao Basin

The episodic hydrocarbon expulsion of overpressure basin is a hot issue in basin fluid research, there are few reports on hydrocarbon-bearing growth faults in source rocks. The study shows that the Qingshankou Formation, the main source rock of the central part of the Songliao basin, develops a hydrocarbon expulsion growth fault, these mid-shallow growth faults were formed at the end of the Nenjiang Formation to the end of the Mingshui Formation. When the excess pressure or overpressure of the source rock reached the bursting limit of the rock, the fractures appeared in the source rock or made the original fault open and grown, the hydrocarbon-bearing fluids were expelled towards the reservoirs either downward or upward, with the expulsion of hydrocarbons, the overpressure decreased gradually, the expelled process tended to be suspended and showed as the lower overpressure belt for the time being. When the source rock excess pressure reaches the source rock fracture limit, the source rock breaks or causes the original fault to start to grow again, the hydrocarbon-bearing fluid undergoes a hydrocarbon expulsion to the lower or upper reservoir, with the discharge of hydrocarbons, excessive pressure is decreasing. The hydrocarbon expulsion process tends to stop, with the release of overpressure fluid, the study area presents three types of hydrocarbons, hydrocarbons, upward hydrocarbons, and upper and lower hydrocarbons, since this hydrocarbon expulsion process occurs multiple times, with the repeated increase in hydrocarbon emissions, the fault distance of the hydrocarbon expulsion fault is also growing. Therefore, the hydrocarbon expulsion period has a good coupling relationship with the fault break growth period. The research results provide a new idea for oil and gas exploration in the upper and lower layers of the overpressure storage tank.