松辽盆地南部深层营城组火山岩气藏成藏条件分析

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

松辽盆地南部深层火山岩气藏已经逐渐成为油气储量的重要增长点。由于勘探程度较低,火山岩气藏的成藏条件研究还不够深入,在一定程度上制约了勘探的成效。从烃源岩条件、储集条件、盖层条件、输导条件以及圈闭条件入手,系统分析了研究区火山岩成藏条件。结果表明,沙河子组发育的大规模煤系地层可以为火山岩气藏提供充足的气源;深层火山岩发育的裂缝系统沟通早期形成的孔、缝、洞,由此构成了研究区良好的储集体系;松辽盆地南部深层火山岩气藏盖层类型多,保存条件较好,泉头组一段顶部泥岩为较好的区域盖层,登娄库组三、四段及沙河子组泥岩是有利的局部盖层,它们为营城组火山岩内部天然气聚集起到良好的封盖作用;研究区天然气输导通道包括渗透性地层、不整合面以及断裂;营城组火山岩圈闭类型较多,其分布主要与构造位置、断层展布、火山岩体等因素相关。

Volcanic gas reservoir in Yingcheng Formation in deep part of southem Songliao Basin has gradually become very impor- tant 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 condi- tions, 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 reser- voir in deep part of southern Songliao Basin, and the sealing conditions are good. The mudstone in first member of Quantou Forma- tion 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 For- mation, and their distribution is mainly related with structural location, fault distribution and volcanic rocks.