Evolution Mode On Shale Fracture Based On Acoustic Emission Behavior

In this thesis,the AE(Acoustic Emission)signals generated by the fracturing expansion of different brittle shale fractures are taken as the entry point.Through the wavelet analysis and discrimination of the AE signals,the inherent law of tension fracturing,shear fracturing and mixed fracturing of different shales which have different brittleness when fractures interact with each other as fracturing.The specific research work and research results of the subject include the following aspects:Firstly,the multi-fractal description method of multi-scale fractures in shale reservoirs is studied.A method for qualitative brittleness index identification of shale rock mass considering multi-scale natural fractures is established.Study on 3D localization of AE source for rupture of rock mass by wavelet analysis.The new brittle index is introduced into the AE propagation equation,and the wave propagation equation of the crack propagation and the moment tensor method are established.Secondly,the rock mass fracture and the AE signal are tested,and the AE characteristics of the rupture through different rock mass which have different brittleness are carried out.Based on the method of moment tensor identification,the fracture law of different brittle shale rock mass is studied.The results show that: when the brittleness intensity of the rock mass is small,the AE response time is more dispersed,the rock mass is delayed and the single rupture surface is mainly surrounded by the regular rupture surface.Contrastively,the AE response time is more concentrated,the rock mass mutated ruptures.The rupture of the rock mass is diversified,and many rupture surfaces appear,and the AE is distributed in the rock mass.The rupture of the rock mass appears both of the damping characteristics of the plastic fracture and the multi-modal brittle fracture.Once more,the damage variable of fractured rock mass fractured and fractured is defined based on the AE count.Based on the AE response characteristics,the fractured abrupt model of fractured rock mass is established.Based on the energy release and the AE wave equation,the intrinsic relationship between the fracture evolution and the AE behavior of the rock mass is studied.Finally,the joint test of hydraulic fracturing and AE of shale is carried out and the interaction between natural fractures and hydraulic fractures of different brittle shales is studied based on acoustic tensor tensor method.The results show that the fracture network is the result of the interaction between the natural fracture and the hydraulic fracture,and the coexistence of tension fracture,shear fracture and mixed rupture.The existence of natural fractures not only disturbs the transition from the evolutionary expansion model to the shear and mixed evolution model,but also induces the evolution of the shear fracture evolution pattern of the natural fracture itself,and the complexity of surface and the difficulty of complexity of fracture network are increased.And the brittle characteristics of shale rock mass have a controlling effect on the action between fractures.From the point of view of AE,it is revealed that the brittleness of rock mass is stronger and easier to form the general rule of fracture network.In conclusion,the general law of fracturing rupture of fractures of hydraulic fractures with natural fractures is studied from the AE characteristics of rock mass rupture.The topics and research contents of this topic have opened up new ideas and research methods for the study of the damage and rupture behavior of fractured rock mass and the evolution mechanism of fracture network system,which is of great significance to clearly understand the formation law of fracture network system of shale fracturing and to lay the scientific foundation for the evaluation of the effect of shale fracturing reservoirs based on AE parameters and waveform characteristics and the study of fracturing construction and parameter optimization.