天然裂缝对页岩气储集和渗流有重要影响,但目前对页岩构造裂缝研究不够深入。本文通过露头、岩心裂缝观察和分析,探讨了渝东南下古生界页岩构造裂缝类型、形成机理及分布控制因素。基于裂缝特征及力学成因,将剪切裂缝分为高角度剪切裂缝、倾斜滑脱裂缝和水平滑脱裂缝。倾斜滑脱裂缝是在上覆岩层重力和水平构造应力共同作用下沿应力集中的软弱面发生剪切滑动形成,水平滑脱裂缝是在构造挤压应力作用条件下主要沿页理面方向的剪切或层间滑动形成;页理发育程度及岩层曲率是控制水平滑脱裂缝形成的关键因素,岩石矿物组成、构造作用及岩层厚度是控制其它类型构造裂缝形成和分布的主要因素,页岩岩石力学层的划分需要根据裂缝特征、岩性变化特征、岩石力学参数及沉积界面等综合确定,岩层厚度与层间构造裂缝密度呈负相关关系。
Natural fractures are important for accumulation and percolation of shale gas. At present,research on tectonic fractures in shale is still not deepgoing. Fractures on outcrops and cores are observed to discuss genetic types,formation mechanism and controlling factors for tectonic fractures distribution in Lower Paleozoic shale in Southeast Chongqing. Based on their characteristics and mechanical geneses,shear fractures are divided into high-angle shear fractures, inclined detachment fractures and horizontal detachment fractures. Under combined action of upside rock mass gravity and horizontal tectonic stress,inclined detachment fractures are formed by shear sliding along stress centralized weak plane. Shear stress along lamellation under structural extrusion and that caused by interlayer sliding formed the horizontal detachment fractures. Degree of lamellation development and stratum curvature are the dominant geological factors that controlling formation and distribution of horizontal detachment fractures. Rock mineral composition,tectonic stress and stratum thickness are the main geological factors that controlling formation and distribution of other kinds of tectonic fractures. Lithomechanics formation is divided according to fracture characteristics,lithology changes,rock mechanical parameters and sedimentary boundaries comprehensively. Stratum thickness and interlayer tectonic fracture density have a negative correlation.