1. Key Laboratory of Shale Gas Exploration， Ministry of Land and Resources， Chongqing Institute of Geology and Mineral Resources， Chongqing 400042；2. Chongqing Engineering Research Center for Shale Gas Resource & Exploration， Chongqing Institute of Geology and Mineral Resources， Chongqing 400042；3. Chongqing Shale gas Research Center of State Key Laboratory of Petroleum Resource and Prospecting，Chongqing 400042
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.
Yue Feng,Cheng Lijun,Jiao Weiwei et al. Controlling factors for formation and distribution of tectonic fractures in Lower Paleozoic shale in Southeast Chongqing[J]. Chinese Journal of Geology, 2016, 51(4): 1090-1100.