Abstract: Facies sequence of volcanic rocks is predominantly controlled by lithotypes in the Songliao Basin. Acidic eruption cycles generally begin with explosive facies and end with extrusive facies. Andesitic/basaltic eruption cycles usually begin with effusive facies and end with volcanogenitic sedimentary facies. Interbeded acidic-intermediate-basic volcanic eruption cycles have complex facies sequence ge-nerally from effusive facies through explosive facies to volcanogenitic sedimentary facies. Weathered crust and sedimentary intercalation are indicative of volcanic intervals. Extrusive and volcanogenitic sedimentary facies are the end-members of an eruption cycle. Facies model described here has been effectively used in seismo-reservoir interpretation in the gas field of volcanic rocks of the Songliao Basin. Only four of the 15 volcanic sub-facies can form high-quality volcanic reservoirs, which include volcanic neck, pyroclastic-bearing lava flow, upper effusive and inner extrusive sub-facies. Well understanding about volcanic facies can make gas exploration easier and more effective: volcanic reservoir exploration → effective reservoir finding → focusing on seismic analytic interpretation of the best four types of volcanic sub-facies which can become potential good reservoirs.

Key words: Songliao Basin, volcanic facies, volcanic reservoir, facies sequence law model, deep-basin gas field beneath Daqing oil field