Abstract:

The research documented in this paper takes the Xingcheng and Shengping volcanic reservoirs in the Xujiawuzi fault depression in the deep of the Songliao basin as study targets. It focus on the controlling effect of the volcanic bodies upon the horizontal and vertical distribution，waterˉgas relationship，caps，pooling types of the gas reservoirs. Thanks to the volcanic bodies，these reservoirs have wide vertical distributions and can occur in a depth up to 4000 to 5000 meters and show features of vertical superimposition of multiple gas reservoirs and lateral beaded distribution. The gasˉwater relationship in the volcanic gas reservoirs is complicated and controlled by the volcanic bodies and eruption periods. Each volcanic body owns isolated gasˉwater systems，but with initor within the same well，there may be several gasˉwater systems. Volcanic gas reservoirs feature in selfˉaccumulation and selfˉsealing and therefore regional seals are not the major condition for hydrocarbon pooling. In general，there are four types of volcanic reservoirs. Among them，the structuralˉlithologic complex gas reservoirs are predominant and controlled mainly by lithology and occur mostly at the structural highs，while the lowˉamplitude anticli nalˉlithologic complex gas reservoirs can only be found in volcanic rocks. They are harbored in a kind of specific anticline formed during volcanic eruptions.

Key words: gas reservoir characteristic, volcanic body, volcanic gas reservoir, Songliao Basin