Calculating the formation period of fault lateral sealing and its application

The study aims to find out the formation period of fault traps near faults in petroliferous basins,based on an analysis of the formation period of fault lateral sealing and related influential factors.A method to calculate the formation period of fault lateral sealing(i.e.the time when displacement pressure of fault rock is equal to that of reservoir rock in fault wall with hydrocarbon migration)is established by comparing the relationship between displacement pressure and time for fault rock and reservoir rock.This method is then applied to the study on reservoirs in the 1^(st),2^(nd),and 3^(rd) members of Dongying Formation(E_(3)d^(1),E_(3)d^(2) and E_(3)d^(3))in terms of formation period of lateral sealing of F3 fault crossing the three reservoirs in the No.5 structure of Nanpu Sag in Bohai Bay Basin.The results indicate that the formation period of the lateral sealing in the studied reservoirs can date from 7.1 Ma,7.4 Ma and 9.2 Ma respectively,all prior to the hydrocarbon accumulation period(about 2.58 Ma).Hence,it can be concluded that these reservoirs are favorable for the accumulation and preservation of hydrocarbons generated from the underlying source rock E_(3)s^(3),and the method proposed is feasible in calculating the formation period of fault lateral sealing.