Abstract: Based on gas diffusion mechanisms and classified systems under multi-gas supply, the estimation method of gas diffusion loss amount is established and applied in estimation of the gas diffusion loss amounts up to surface of four sets of main source rocks in northern Songliao basin. The resulted amount of 39.46×10¹²m³ accounts for 27.3% of the total amount of generated gas in source rocks, showing that gas diffusion is a significant factor for gas resource evaluation.

Key words: Songliao basin, gas source rock, oil source bed, natural gas, diffusion coefficient