以四川盆地长宁地区宁201井区页岩储层为例,借助三维地震体和其蚂蚁追踪体地震属性开展了构造精细解释,应用有限元层拉平、正交分解主成分分析、自动断层片提取和古应力场反演等技术,并结合已有区域构造地质认识和单井裂缝信息,对地震尺度断裂系统进行了分期与配套,不仅重新厘定了区域构造演化序列,而且实现了区域构造和油藏级别不同尺度裂缝系统之间的有机匹配.分析结果表明:①影响目的层地震尺度断裂系统发育的主要构造活动发生于燕山期—喜马拉雅期,主要包括燕山晚期构造幕的近S—N向挤压作用、喜马拉雅早期构造幕的NNE—SSW向挤压作用以及喜马拉雅中期构造幕的NWW—SEE向挤压作用;②燕山晚期构造幕主要形成近EW向长轴背斜和向斜、近EW向逆冲断层和断层相关裂缝,以及多个方向的褶皱相关裂缝;③喜马拉雅早期构造幕主要形成了成因上相关联的共轭断裂系统,包括走滑断层和剪切裂缝(NNW向和NE向2组)以及横向扩张裂缝;④喜马拉雅中期构造幕主要形成NNE—NE向逆冲断裂和伴生褶皱,以及横向扩张裂缝.研究成果对于页岩气勘探开发区离散型裂缝建模、钻井工程预警,以及完井、开发方案优化等都有着非常重要的石油地质意义.

Taking the shale reservoir of well Ning 201 area of Changning Block of Sichuan Basin as an example, seismic structural interpretation was carried out based on original seismic amplitude cube and derived ant-tracking cube, and then the technologies of finite-element horizon flattening, orthogonal decomposition principal component analysis(PCA), fracture/fault patch auto-extraction, paleo-stress field inversion were applied, combined with the existing regional structural geological knowledge and single well fracture information, to figure out the staging and grouping of seismic-scale fracture system, at the same time to clarify the regional tectonic evolution and its genetic relationship with fractures at different scales. The following results were obtained：(1) the main tectonic movements that affect the development of the seismic-scale fracture system of the target interval occurred in the Yanshanian-Himalayan periods, including the near S-N compression of the late Yanshanian tectonic episode, the NNE-SSW compression of the early Himalayan tectonic episode, and the NWW-SEE compression of the middle Himalayan tectonic episode; (2) the Late Yanshanian tectonic event mainly formed the near E-W long-axis anticlines and synclines, near E-W thrust faults and fault-related fractures, and fold-related fractures in different directions; (3) the Early Himalayan tectonic event mainly formed genetically related conjugate fracture sets including strike-slip faults and shear fractures both in NNW and NE directions, and transverse extensional fractures;(4) the Middle Himalayan event chiefly formed thrust faults, and related fractures and folds in NNE-NE direction, and transverse extensional fractures. It is concluded that such analysis of seismic-scale fracture system for specific shale gas reservoirs is of great significance in building discrete fracture model, providing precautionary advice for drilling engineering, and optimizing well completion program and field development plan, etc.