AN ANALYSIS OF EXPLORATION POTENTIAL OF VOLCANIC GAS POOLS IN CHANGLING FAULT DEPRESSION

Deep volcanic rocks are well developed in Changling fault depression in the central-southern Songliao Basin.The reservoiring conditions of the volcanic gas pool are complex and the exploration is of great difficulty.The results of exploration potential analysis will influence the decision-making for exploration in the next step.The reservoir and trap conditions,potentials of source rocks,and reservoiring patterns of the volcanic gas pools in the study area are studied.The following conclusions are obtained.①Multi-stage volcanic rocks with both primary and secondary pores are vertically superimposed in Changling fault depression,and compose unique volcanic reservoirs.②The spatial combinations of the volcanic rocks with major basement faults and the surrounding rocks in the special tectonic setting lead to the formation of lithologic traps,and volcanic lithologic and structural combination traps.③The various source rocks in deep of the fault depression provide rich hydrocarbons for the volcanic reservoirs.④The interbedding of the volcanic reservoirs and source rocks results in the gas pools with hydrocarbons generated by and accumulated in the same strata,and that with hydrocarbons generated by the source rocks below and accumulated in the reservoirs above.The temporal and spatial combinations of the source rocks and reservoirs are favorable for the formation of middle and large gas fields with volcanic pools as the targets.