Structural Characteristics And Its Control Of The Fracture Of Shales In The Longmaxi Formation, In Southeastern Chongqing

Based on the observation of geologic structure in field, combined with theanalysis of regional tectonic setting, the paper discussed the structural evolution andits controls of the Fracture of shales in the Longmaxi Formation, in SoutheasternChongqing. Rock samples which collected from different parts of the structure inLongguxi anticline, and all samples were described macroscopically.16shale samplesand some of core samples were selected for micro deformation and porosity tests. Themicroscopic fracture characteristics and porosity structure of shales in the LongmaxiFormation were studied deeply.Studies have shown that nanchuan areas affected by Indo movement, Yanshanmovement and Himalayan movement, which formed NE direction oriented folds andfolds axial protruding NW. Combined with practical field work and geologicalanalysis, the paper focused on the discussion is Longguxi anticline in nanchuan areas.Structural controls the rock fractures mainly as the density and the degree ofopening of fractures, and the tectonic stress controls the direction of fractures and theformation of the times, and the late tectonic deformation control the microscopicfracture. Changes in the South East Wing of Longguxi anticline in limestone crackslinear density is not very obvious, but there is a certain relationship with the distancefrom the core of the fold; Under the control of modern tectonic stress field, Longmaxishale cracks50°~60°direction is easy to open; Shales fractures in LongmaxiFormation was under the combined effect formed in the multistage and differentdirections tectonic stress of field, NW or NNW fractures primarily match the lateYanshan-early Himalayan tectonic stress field, NW and NNE fractures major matchHimalayan late tectonic stress field; After extrusion of rock diagenetic, shalereservoirs will make it easier for developing micro-fractures, can also be found bymechanical experiments, originally not developed natural fractures of samples formdifferent types of fractures after mechanics test.