Northern Songliao Basin And The Main Source Rock Gas Diffusion Loss Estimate

Based on studying element motion theory and geological, this paper studied the diffusionmechanism of gas in strata. According to Pick's law, based on simplifying complex geologicalproblems, this established geological model and mathematical model of gas diffusion. Accordingto amount and distribution of gas diffusion sources in strata section, this paper put forward amethod dividing the gas diffusion systems in strata section. Using simulation experiments andEinstein's equation, this paper established a method correcting measured gas diffusion coefficientin strata condition. According to the research results of Fuxiaotai etl (1996), this paper establisheda method calculating the gas-bearing concentration in strata water. According the mature area ofhydrocarbon sourcerock, this paper determined the gas diffusion area. According to the generationhydrocarbon ctrical time, this paper determined the beginning time of gas diffusion. According tothe formation time of upward concentration caprocl, this paper determined the stopping time ofgas diffusion. Based on calculating gas diffusion loss amount from each gas diffusion system, thispaper calculated total gas diffusion loss amount in the condition of many diffusion sources by themethod of adding up. Based on above-mentioned researches, this paper divided four gas diffusionsystems in the north of Songliao Basin. According above-mentioned research methods, this paperestimated the gas diffusion amount of four hydrocarbon sourcerocks in each geological period inthe north of Songliao Basin. The results are that the gas diffusion amount of K1Sh+yc, K1d2, K1qnand K1n1+2 sourcerocks is 10.8×1012m3, 5.55×1012m3,13.44×1012m3 and 9.67×10l2m3. Thepercentage of it accounting its generation gas amount is 18.8%, 100%, 25.6% and 54.8%.Therefore, diffusion id the important factor influencing gas reserve evaluation.