Sanzhao Depression is an important oil and gas exploration region in Songliao Basin and Fuyu oil layer is the main gas productive layer. Based on the Fick First Law

the total gas diffusive flux of Fuyu layer in the depression is calculated through geological resumption of natural gas difusion coefficient and etc. The result indicates that the gas diffusive flux of Fuyu oil layer in Sanzhao Depression is 27. 39% of the total gas generation amount of the source rocks. Fuyu oil layer must get much more gas amout than 27. 39 %of gas generation amount from the source rocks

and has surplus gas to form gas pools

otherwise the gas of the layer would be completely lost and no gas deposit could be found.Therefore

it has been demonstrated that the action of gas diffusion is an important factor that can not be neglected in natural gas reserve evaluation.