In Shiwu fault depression of Songliao Basin

sediments buried shallower than 1 250 mbelong to normal pressure zone;that deeper than 1 500 m belong to low-pressure zone sediments between above mentioned zones are in tranzitional zone. Hydrodynamic fields corresponding to these zones are respectively free replacing zone

obstructive replacing zone and irreplacing zone. The amounts of gas losses in the obstructive replacing and irreplacing zonesare greater than that of subsurface water leakage recharge

and the deeper the gas buried

theless the subsurface water recharge amount would be. This resulted in the decrease of

essurecoefficient with the Increasing of buried depth

and the formation of low-pressure gas pools. Itis considered that gas reservoirs in the obstructive replacing zone and irreplacing zone are themain productive beds of the region.