焦石坝地区构造变形差异及保存条件解析

Analysis of Tectonic Deformation Difference and Preservation in Jiaoshiba Area

构造变形是影响复杂构造区页岩气保存条件、控制页岩气差异富集的关键。通过对焦石坝地区的构造解析,从纵向上建立了以前寒武系基底、中下寒武统膏盐、下志留统泥岩为滑脱层的多重滑脱变形模式;从横向上建立起由南东往北西方向的递进扩展变形模式。结合构造变形特征、构造样式,划分出东部压扭变形带、西部断滑(断展)褶皱变形带两个变形带,前寒武系滑脱断层的结构是导致焦石坝地区差异构造变形的主要原因。分析认为具有背斜构造背景、宽缓的构造样式的地层,构造变形较小、地层相对较完整,对页岩气的保存较为有利;而受大型逆冲断层活动强度大的地层,其控制的高陡构造顶部地层剥蚀严重、伴生断层及裂缝较发育,不利于页岩气保存。

Tectonic deformation is the key to influence the shale gas preservation in complex structural form and control the differences enrichment in shale gas. According to the analysis of structural construction in Jiaoshiba, this paper have built the multiple decollement deformation pattern of the detachment layer with upper Cambrian system basement, middle lower Cambrian pestiferous salt and lower Silurian mudstone in vertical dimension in parallel dimension, and have built the progressive expanded into detachment from SE to NW in horizontal dimension. Combined the tectonic deformation feature and tectonic pattern style, it can divided into two deformation belts, such as compress shear fault fold belt in eastern part and compress shear skew belt in western part. This analysis suggests that the tectonic deformation of the tectonic pattern in anticline and wide-gentle is small, the formation is relatively developed completely, that is favorable for the preservation of the shale gas; A large scale thrust fault has high activity intensity, the top formation of the high-steep tectonic which controlled by the thrust fault has strong denudation, sub fault and well-developed fractures, it does not favor the preservation of the shale gas.