Analysis of the Accumulation Conditions for Volcanic Gas Reservoirs in Deep Yingcheng Formation, Southern Part of Songliao Basin

Volcanic gas reservoir in Yingcheng Formation in deep part of southern Songliao Basin has gradually become very important in increasing the oil and gas reserves. Due to the low degree of exploration, study on the accumulation conditions for volcanic gas reservoir is insufficient, influencing the effectiveness of exploration to some extent. In this paper, the accumulation conditions for volcanic gas reservoir have been analyzed systematically, including the source rock conditions, reservoir conditions, sealing conditions, conducting conditions and trap conditions. The study results show that large-scale coal-bearing strata in Shahezi Formation can provide sufficient gas for volcanic gas reservoir; the fracture systems in deep volcanic rocks can communicate the earlier developed pores, fractures and caves, resulting in good reservoir systems in the study area; there are various caprock types in volcanic gas reservoir in deep part of southern Songliao Basin, and the sealing conditions are good. The mudstone in first member of Quantou Formation is better regional seal, mudstone in third and fourth member of Denglouku Formation and Shahezi Formation are favorable local seals, with good seal capability for the gas communication in volcanic rocks of Yingcheng Formation; gas transporting pathways in the study area include permeable formation, unconformity and faults; there are various trap types in volcanic rocks of Yingcheng Formation, and their distribution is mainly related with structural location, fault distribution and volcanic rocks.