Controlling of Faults to Gas Accumulation of Volcanic Rock in Depression Basin:An Example from Xujiaweizi Depression of Songliao Basin

There are mainly the western Xujiaweizi early extensional strike-slip fault system,central Xujiaweizi strike-slip long-term active fault system,eastern Xujiaweizi strike-slip fault system,early extensional and later tenso-shear long-term active fault system,and later tenso-shear fault system according to the study of development and distribution of faults,gas distribution regularity in volcanic rocks and their relationship in Xujiaweizi depression.The main active periods of the faults are K1h-K1yc3 and the later of K1q2 to K2qn.There are many distribution layers in vertical,much depth range,located in or near gas source depression in plane and along faults on gas distribution features in volcanic rocks.Control roles of gas accumulation and distribution in volcanic rocks are manifested in the following areas: faults control formation and distribution of gas source rocks;faults control formation and distribution of volcanic rock body and fractures within them;faults control formation and distribution of gas traps in volcanic rocks;faults control formation layers of gas reservoirs in volcanic rocks.