四川盆地普光超大型气田的形成机制

Generation mechanism of Puguang Gas Field in Sichuan Basin

普光气田是在四川盆地勘探过程中发现的最大气田,也是我国海相碳酸盐岩层系最大的气藏。除储量规模最大外,普光气田也是四川盆地目前已发现的气藏中埋藏深度最大、资源丰度最高、储层性质最好、优质储层最厚、天然气中硫化氢含量最高、天然气干燥系数最大的整装气藏。普光大型气田的特殊性与该区经历过独特的成烃、成岩和成藏作用有关,油气的高度富集源自:多套烃源岩和优质烃源岩的多期次充注;疏导体系与生、排烃过程形成动态匹配;储层发育在蒸发岩台地边缘高能鲕粒滩相沉积相带中,并受到后期白云化作用和深埋条件下酸类的强烈溶蚀改造,致使次生孔隙空前发育;构造古隆起与长期接受供烃,硫酸盐热化学反应(TSR)的发生与储层次生孔隙的大量生成和储集性能的优化,飞仙关组上覆嘉陵江组和雷口坡组厚层膏岩的有效遮挡。

Puguang Gas Field as the largest gas field of Sichuan Basin is also the biggest marine carbonate formational gas reservoir. In addition, Puguang Gas Field has highlights in several aspects such as the deepest burial condition, the highest reserves abundance, excellent reservoir quality, the thickest reservoir bed, the highest quantity of H2 S and the biggest dry coefficient of natural gas. Puguang Gas Field has the special condition of reservoir-forming, which is in virtue of some factors, including the repeated infusion of the multiple hydrocarbon and high quality of hydrocarbon, the dynamic matches of channel system and the processes of generation and expulsion of hydrocarbon, the development of reservoir bed at the edge of evaporated plateau and the high-energy oolite facies, the highly formation of the secondary porosity due to the late dolomization and intense acid corrosion, the paleo-tectonic bulges and long-term received hydrocarbon, the occurrence of thermochemical sulfate reduction and the highly development of secondary porosity in reservoir bed, the optimism of the performance of reservoir bed, as well as the effectiveness barrier of thick gypsum rock in Jialingjiang and Leikoupo formations overlying Feixianguan Formation.