Reserch On Formation, Evolution And Effection On Seal Of Faults Of High Overpressure In K₁qn₁ Mudstone In Binbei Area

By taking full advantage of available seismic data of research area, studying the features of structural evolution, and researching the development and evolution features of the faults in every seismic reflecting horizon, it was conclude that the faults mainly come through 3 great structural movement time which was rift, downwarping and structural reverse, and there are mainly four types of faults: faults that formed in rift period and continued their activities in downwarping period, faults that formed in downwarping period, faults that formed in rift period and continued their activities in downwarping period and structure reverse period, faults that formed in downwarping period and continued their activities in structure reverse period. By analysising interval travel time of every prospecting wells in 3 chief cut plane, the overpressure of K1qn1 mudstone was studied, and it was conclude that the bandwidth and amplitude of overpressure of K1qn1 become narrow and small, and the overpressure was more development in Suihua depression and Heiyupao depression. Based on equivalent depth method, it was studied how the recent overpressure of K1qn1 mudstone developed and distributed by using the date of nterval travel time of more that 100 prospecting wells in Binbei area, and it was found that the overpressure of K1qn1 mudstone only distributed in the south of Binbei area, the maximum was 13.5MPa, and the most development area were in Qijia and south of Heiyupao depression. By the inversion result of overpressure of K1qn1 mudstone of every prospecting well, it was confirmed that the evolutionary precess of overpressure of K1qn1 mudstone was the mode which was overpressure released while faults moved. And based on above, it was researched that the oil-gas of K1qn1 migrated downward in the end of Eogene, and then it was found that the oil-gas migration area was only in central depression, the maximum of migration depth was 332m where was in the south of Sanzhao depression, Anda area., and the oil-gas could migrate into the Y oil layers through the F oil layer in the most migration areas downward. Making the use of the theory of seal of faults under the condition of overpressure, the sealing property and its evolution history of faults which cut off K1qn1were studied based on sufficiently analysising the distribution characteristics of faults, and it was concluded that most of the faults which cut off K1qn1 were vertical sealed faults, and there were a few poor vertical sealed faults which distributed in Suileng anticlinal belt and Qianyuan structural belt. Furthermore, the time for most of the faults to form vertical sealing were earlier than that when the oil-gas discharged from the sourcerock. Finally, synthesizing the research above, it was found that the area for oil-gas accumulation was controlled by the area of oil-gas migration downward; the the validity to seal the oil and gas for overpressure was good because it was earlier for overpressure formation than that a great quantity of oil-gas discharged from the sourcerock; the high value area of overpressure was favorable area for oil-gas preservation; and the recent vertical sealing property and its evolution history of faults which cut off K1qn1 were favour of the oil-gas accumulation and preservation, after the affection of overpressure of K1qn1 mudstone to oil-gas accumulation, distribution and preservation was analysised.