川中安岳气田灯影组气藏构造演化特征及控藏机制

The structural evolution characteristics of the Sinian Dengying Formation gas reservoir and its controlling mechanism in the Anyue Gas Field,Sichuan Basin,China

研究四川盆地中部安岳气田震旦系灯影组气藏构造演化特征及气藏的控制作用,探讨成藏规律。利用高分辨率三维地震资料以及四川盆地大格架二维地震资料,采用三维可视化技术、平衡剖面技术和地质建模技术,分析构造演化过程,探索川中地区西部主动拉张裂谷形成机制,建立储层地质模型,总结成藏的主控因素。结果表明:桐湾Ⅰ幕与桐湾Ⅱ幕构造运动形成了2期贯穿南北的大型主动拉张裂谷,2期裂谷形成的时期不同,空间上独立。主动拉张裂谷形成机制为"先抬升剥蚀,后拉张下陷",具有两幕性。主动拉张构造演化过程形成了灯二段与灯四段2套储层,每套储层的岩溶又分为抬升剥蚀和拉张下陷后暴露风化剥蚀2个阶段。在2个不同岩溶阶段中,岩溶中心从早期的西部迁移至晚期的东南部,且靠近裂谷的台缘带始终为储层发育的有利区;在气藏构造演化过程中,形成了高石梯古隆起以及磨溪-龙女寺长轴古隆起2处有利古构造,并始终保持着继承性发展,且主动裂谷内的烃源岩在气藏西边界形成了岩性封堵,两者共同控制着有利的成藏聚集条件,最终高石梯古隆起发展为最高古构造,为最有利油气聚集中心。桐湾运动的2幕主动拉张作用是形成灯二段与灯四段2套独立气藏的关键因素,台缘带为储层发育有利区,高石梯地区为油气聚集有利区。

The tectonic evolution characteristics and its control effects on the Sinian Dengying Formation gas reservoirs in the Anyue gas field of central Sichuan Basin are discussed.On the basis of 3D high resolution seismic data and 2D seismic data,with the application of 3D visualization technology,balanced profile technique and geological modeling technique,the tectonic evolution of the gas reservoir is analyzed,the formation mechanism of extensional rift in the west central Sichuan is explored,the geological modeling of reservoir is established and the major controlling factors of gas reservoir formation is summarized.It shows that the first and the second stages of Tongwan tectonic movement formed active extensional rift running from the north to south,with different formation time and independent locality.The formation mechanism of rifts is characterized by initial uplifting and denudation,followed by extension and depression.During the active extensional tectonic evolution process,two sets of reservoirs developed in the Member 2 and Member 4 of Dengying Formation.The karstification of each reservoir is subjected to two stages of initial uplifting and denudation,and then weathering and denudation.From early to late stages,the karstification center moves from west to the southeast,and the marginal zone of platform is the favorable area of reservoir development.Two major favorable paleo-uplifts,the Gaoshiti paleo-uplift and the Moxi-Longnüsi paleo-uplift,formed in the structural evolution process.A lithological sealing occurs in the west rim of the gas reservoir and both the paleo-uplifts and the lithological sealing control the favorable gas accumulation.Eventually,the Gaoshiti paleo-uplift developed as the highest paleo-structure and as the most favorable gas accumulation center.It is considered that the active extension of Tongwan movement is the key to the formation of the Dengying Formation Member 2 and Member 4 gas reservoir.The platform marginal zone is a favorable area for reservoir development,and the Gaoshiti area is a favorable area for oil and gas accumulation.