Abstract:

The pore diameters of argillaceous caprock decreases as its buried depth increased.Only when the pore diameters are as small as or even smaller than the diameters of oil and gas moleculars,the argillaceous caprock could seal completely every states of hydrocarbon,and reach the sealing critical point.According to this rule,the sealing threshold depths of argillaceous caprock for both oil and gas could be calculated.Then the corresponding threshold time value could be calculated based on bed thickness and the rate of deposition.According to Φ_m=54.74 exp(-0.000 935 4z),K=0.136(Φ_e)^4.4/S_WB)² and r=√8K/Φ,the critical threshold depth for sealing oil in Sanzhao Region,Songliao Basin should be 2 500-3 000 m,and the critical threshold depth for sealing gas should be 5 000-5 200 m.This does not inclode the sealings of capillary pressure,abnormal pore fluid pressure and dense oil and gas.