焦石坝地区构造特征及页岩气保存模式研究

摘要

针对焦石坝构造特征及页岩气保存模式认识不清的问题,选取焦石坝周缘砂岩样品及NW—SE向地质剖面,利用显微构造分析、平衡剖面技术,对焦石坝在地质历史时期应力方向、主要形变过程及形变时期进行研究.研究结果表明:焦石坝地区具有构造改造强度弱、改造时间晚、断层封堵性好、埋深适中以及良好的顶底板岩性组合的页岩气保存模式;在地质历史时期主要受NW—SE向的挤压应力影响,NE—SW向应力次之,主要形变期在120 Ma之后,地层总缩短量为3.8 km,缩短率为16.7%,其中65~85 Ma(燕山晚期)是焦石坝主要隆升阶段.该研究对四川盆地周缘页岩气勘探开发具有重要指导作用.%The sandstone core samples in the Jiaoshiba periphery and the NW-SE geologic cross-sections are taken to further characterize the structure and identify shale gas preservation pattern. Microstructure analysis and balanced cross-section are used to study the stress direction,major deformation process and deformation period of Jiaoshiba in the geologic history. Research indicates that the shale gas preservation pattern in Jiaoshiba is featured by weak tectonic reworking,late reworking time,better fault sealing,moderate buried depth and favorable top-bottom li-thology combination.It is mainly affected by the compressive stress along the NW-SE direction in the geologic histo-ry period,followed by the NE-SW stress.The major deformation period is after 120 Ma,the total formation shorten-ing is 3.8 km with a shortening ratio of 16.7%,where 65 ~ 85 Ma(Late Yanshan Period)is considered as the predominant uplifting stage of Jiaoshiba.This research could provide a significant guidance for the shale gas explora-tion and development in the periphery of Sichuan Basin.