开江—梁平海槽周缘二叠系—三叠系礁滩型气藏是四川盆地天然气勘探开发的重点领域,但深层(＞4500 m)碳酸盐岩储层致密,制约了天然气藏的高效勘探与开发.基于重新处理的三维地震资料,开展走滑断裂的地震识别,研究走滑断裂的构造特征,并结合钻井资料分析走滑断裂控藏作用与天然气富集规律.结果表明:开江—梁平海槽地区发育一系列北西向的走滑断裂带,具有纵向分层、平面分段特征.剖面上走滑断裂多表现为直立型断裂与花状断裂多层叠置,平面上断裂组合以斜列、侧列为主,形成线性构造、雁列构造、花状构造、马尾状构造等多种构造类型.走滑断裂位移小、成熟度低,经历震旦纪末—早寒武世、前二叠纪、二叠纪—三叠纪等3期走滑断裂活动,具有连接生长机制与继承性发育的特征.走滑断裂带裂缝发育,断裂及其相关溶蚀作用控制了优质储层的发育,可导致碳酸盐岩渗透率增长超过1个数量级、孔隙度增长超过1倍.走滑断裂不仅沟通海槽内的二叠系烃源岩,形成侧向运移优势通道,而且可垂向连通深部烃源岩,形成断裂输导、复式成藏的多个含气层.开江—梁平海槽周缘台缘带及台内与走滑断裂有关的深层碳酸盐岩气藏的勘探开发潜力巨大,是值得深入探索的有利新领域.

Large quantity of the Permian-Triassic reef-shoal gas reservoirs have been discovered in Kaijiang-Liangping trough, which is an important area for increasing reserve and production in the Sichuan Basin. However, there are many dense reservoirs in deep strata more than 4 500 m in this area, so it is important to find fault-related sweet spot reservoirs for efficient gas reservoir exploration and development. Based on the 3D seismic reprocessing and interpretation of strike-slip faults, the structural characteristics of strike-slip faults are studied, and the reservoir controlling factors and favorable exploitation directions related to the strike-slip faults are analyzed combining with drilling data. The results show that a series of NW-trending strike-slip faults are developed in Kaijiang-Liangping trough. The strike-slip faults are mainly of vertical and flower-like faults in the section, and oblique and lateral faults in the plane. There are multiple types of structures such as linear structure, en echelon structure, flower structure, horse-tail structure, which are characterized by vertical stratification and planar segmentation. The strike-slip fault has small displacement and low maturity, and has experienced the late Ediacaran-Early Cambrian, pre-Permian and Permian-Triassic activities, and has the characteristics of linkage growth mechanism and inherited evolution. It is shown that fractures are developed in strike-slip fault zone, and they subsequent increase carbonate rock's permeability by more than one order of magnitude, and fracture-related dissolution porosity by more than one time, which play an important constructive role in carbonate reservoir. At the same time, the strike-slip faults not only form the dominant lateral migration channels connecting to the Permian source rocks in the trough, but also may vertically connect the deep Cambrian and Ordovician-Silurian source rocks to form multiple gas-bearing layers with the faults playing role of transportation and accumulation. The study suggests that there is great potential for natural gas exploration and development of the strike-slip fault-controlled gas reservoirs in the trough-platform margin and intra platform deep carbonate reservoirs in the Kaijiang-Liangping trough, which are favorable new domain that are worthy of further exploration and development in the Sichuan Basin.