Xushen gas field is a typical tight volcanic gas reservoir located in Songliao Basin.With the development of gas reservoir in depth

water breakthrough in wells appears

and the intensive water invasion and rising gas-water ratio have severely restricted the efficient development of volcanic gas reservoir.Therefore

the understanding of inner gas-water distribution

along with its major controlling factors

has becoming a key in enhancing gas well productivity.In the study area

the gas-water distribution is complex in the volcanic gas reservoir

and characterized by "gas on top and water at bottom" overall.Besides

volcanic edifice is the elementary cell of gas-water distribution; there is no unified gas-water interface throughout the study area

while more than one gas-water systems may exist in the same volcanic edifice; and different gas-water systems may share a gas-water interface.Based on the description of volcanic edifices in the Yingcheng Formation

we systematically analyzed the gas-water distribution characteristics of

and clarified the major factors controlling the gas-water distribution in the tight volcanic gas reservoir in Xushen gas field

using production test

as well as some static data in terms of physical property

mercury intrusion porosimetry (MIP) and thin section.The results show that the source rock distribution controls the macroscopic gas-water distribution in the volcanic gas reservoir in the Yingcheng Formation

while the volcanic edifice and structure have jointly had an influence on the accumulation and adjustment of gas

and the complicated microstructure of volcanic rocks is a key to gas-water fractionation in the reservoir.