The Rock Mechanical Characters And Fracture Stress Sensitivity Research Of Dense Reservoir In West Sichuan Basin

The main object of the research is the middle part of dense reservoir in west Sichuan. With the geologic material of the gas pool as the foundation, combining with lithomechanics theory and taking the experiment analysis as the main tool, The test makes the research on Rock Mechanical characters and fracture stress sensitivity.By using"MTS petrophysical data automatic testing system", the text have done deformation,intensive and dynamostatic parameter test. Then, according to the result and relative theory, it analyzed the character of the rock's deformation,dynamostatic parameter and the rules regarding their changing. Finally, it discussed mutual relation of dynamostatic parameters.By using FC-040 formation fracture parameter testing system, the text has made experiment on stress sensitivity of matrix and fracture of sand stone in work area. During the experiment, some factors ,which have effect on sensitivity of fracture, such as: stress changing trace, temperature, filling were all considered. Furthermore, while evaluating the stress sensitive degree of matrix and fracture in workarea's sandstone, the text also analyzed the stress sensitivity mechanism by using lithomechanics character and fracture closure stress experiment. The research shows: In sandstone, the matrix's permeability stress sensitivity degree is far beyond porosity's, and the stress sensitivity of matrix permeability is relevant with dense degree of rock and natural mechanical property; the stress sensitivity of matrix permeability in work area is generally middle to low; The existence of fracture strengths the sensitivity, especially during effective stress stage, permeability falls quickly with the rising of actual stress. The fracture stress sensitivity degree is generally middle to strong; The fracture permeability shows comparative lagging, the recovery degree is comparatively low after a pressuring. The temperature has some effect on both permeability of matrix and fracture, but its degree is far lower than effective stress's. The filling of fracture can restrain the closing of fracture, the harder and more concentrating of filling becomes, the lower the fracture stress sensitivity is. The fracture's closure degree is growing with the stress. It approached max at early stage of stressing and then gradually decreased to the normal. This is coincide with fracture stress sensitivity experiment; The deformation and recovery of fracture has relation with stress history; With different stress degree, the deforming host and deforming level also show differently and represent different stress sensitivity characters.