A Study on Defining the Evolution Stage of Sealing Properties of Fault Zone Filling materials ——Taking the F3 Fault in K1d1 of Beier Depression as an Example

[Objective] The unreasonable division of the evolution stages of the sealing ability of fault zone filling materials makes it impossible to reasonably explain the differences in oil and gas distribution in different parts of fault traps. [Methods] To solve this problem, in this paper, a research method is established to evaluate and evolve the Closure Index and Cement Index for the fault zone filling material and underlying reservoir rock, and then to comprehensively determine the evolutionary stage of sealing for fault zone filling material by comparing the relative size of the the Closure Index and Cement Index between the fault zone filling materials and underlying reservoir rocks over time. [Results] The method was used to determine the evolutionary stage of sealing of the F3 fault zone filling material in K1d1 of Huhenuoren tectonic belt, Beier Depression, Hailar Basin. The results show that: the fault zone filling materials of the F3 fault in K1d1 are in the stage of non-Closure Sealing and non-Cement Sealing at the measurement points 2,4, 6, 9-11, which is not conducive to the accumulation and preservation of oil and gas in K1n2, resulting in no oil and gas display obtained during oil and gas drilling. The fault zone filling materials of the F3 fault in K1d1 at measurement points 1, 3, 5 are in the stage of Closure Sealing at present. However, due to their evolutionary stage of non-Closure Sealing and non-Cement Sealing during the critical period of reservoir formation, no oil and gas was obtained during oil and gas drilling too. The fault zone filling materials of the F3 fault in K1d1 at measurement points 7、8、12-15 are in the stage of Closure sealing and Cement Sealing, which is most conducive to the accumulation and preservation of oil and gas in K1n2. There are oil and gas accumulation at measurement points 7-8 and 12-15 from oil and gas drilling. [Conclusion] Therefore, the method of determining the evolution stage of fault zone filling material sealing ability is feasible, which is of great significance for determining the sealing ability and formation time of fault traps, and improving the efficiency of oil and gas exploration.