川东南泸州地区多滑脱层构造特征及变形机制

Structural Characteristics and Deformation Mechanisms of Multipledetachments in Luzhou area,Southeastern Sichuan Basin

近年来川东南地区页岩气勘探开发逐步向深层领域拓展,尤其是泸州地区显示出3500 m以深页岩气勘探开发的巨大潜力。为了进一步明确泸州地区构造特征及变形机制,依据地震资料对该地区进行了构造解析,采用离散元数值模拟探究了其构造变形的主控因素,恢复了泸州地区中新生代构造演化过程。研究表明:多滑脱层和区域构造挤压是泸州地区构造变形的主要控制因素。受膏盐岩影响,泸州地区发育低陡的盖层滑脱构造,垂向分层明显,形成断展褶皱、滑脱褶皱和滑脱层间隐伏褶皱、双重构造等复合的构造。该区域构造变形主要受下寒武统膏盐岩滑脱作用控制,膏盐岩和页岩滑脱层协调变形向低陡背斜核部聚集。燕山晚期以来,泸州地区多滑脱层沉积伴随区域挤压,发育盖层滑脱的隔档式褶皱;喜山期褶皱带再次隆生,原有的断层和剪切带位移量增大,滑脱层间形成一系列次生断层和隐伏褶皱。背斜处油气藏容易受到破坏,向斜处是页岩气勘探的有利地区,其中对冲型向斜结构相对简单,内部应力相对稳定。

In recent years,shale gas exploration and development in southeastern Sichuan has gradually expanded to the deep areas.The Luzhou area shows great potential of shale gas exploration and development with the depth over 3500 m.In order to further clarify the characteristics and evolution mechanism of various structural deformation in Luzhou area,the main controlling factors of fold belt were explored by using discrete element numerical simulation based on structural analysis of seismic data,and the evolution process of Mesozoic and Cenozoic was restored.And the following research results show that multiple detachment layers and regional tectonic compression are the main controlling factors of structural deformation in Luzhou area.Influenced by multiple detachment layers,Luzhou area has developed low steep thin-skinned structure and obvious vertical stratification,forming complex structure such as fault-propagation folds,detachment folds,buried folds and duplex structures between detachment layers.Among them,the lower Cambrian gypsum rock plays a major role in controlling the deformation,and the gypsum rock and shale slippage coordinate and accumulate towards the core of the anticlines.Since the late Yanshanian,the multi-detachment allochthonous succession with regional compression in Luzhou area were developed the thin-skinned comb-shaped folds.The fold belt rose again in Himalayan,the displacement of the original fault sand shear zones increased,and a series of secondary faults and buried folds formed between the detachment layers.The reservoirs are easy to be destroyed at anticline zones,while the syncline areas are a favorable area for shale gas exploration.The relatively simple deformation for syncline composed of ramp thrusts results in comparable stable internal stress distribution.