Study On Acoustic Emission Signal Detection And Location Recognition Of Rock Rupture

Shale fracturing is when the rock is deformed under the action of external force,and a connected fracture network is generated inside the rock to gather the unconventional oil and gas inside the rock to meet the requirements of large-scale exploitation.At present,shale fracturing technology has been relatively mature in technical equipment,operation and implementation,but there is still a lack of effective means in field monitoring.Therefore,in this paper,microseismic/acoustic emission theory and technology are used to study the acoustic emission activity law of shale fracturing.Based on the acoustic emission signals collected by the indoor uniaxial / triaxial rock compression experiment,the time-frequency analysis,hilbert-Huang transform,time difference 3d positioning method are used as tools.Variational modal decomposition program is used to study the wave property characteristics of acoustic emission signals by MATLAB programming,and the acoustic emission events occurring during shale fracturing experiments are located.The specific research work and achievements include the following aspects:1.Firstly,the indoor uniaxial / triaxial rock compression experiment is carried out.By arranging sensors around the rock samples,the wave signals generated during fracturing are converted into electrical signals,and the signals are transmitted into the acoustic emission monitoring system.The acoustic emission signal of rock rupture is obtained.Based on the data collected in this experiment,the data are provided for signal processing and analysis.2.Empirical Mode Decomposition(EMD)method was used to denoise and reconstruct the acoustic emission signals of rock fracture.By comparing the signal-to-noise ratio and mean square error before and after denoising,the method suitable for dealing with rock rupture signal is selected,and the variational mode decomposition(VMD)method used in this paper is provided.3.The process of rock rupture can be expressed by the characteristics of acoustic emission signals.The variational mode decomposition method is used to study and process the acoustic emission signals of rocks to obtain the characteristic laws of rock rupture.Moreover,by studying the VMD algorithm and introducing parameters such as kurtosis and Hausdorff distance,the VMD-Wavelet denoising algorithm based on variational mode decomposition and wavelet transform is used,.K modal functions are obtained by variational mode decomposition of acoustic emission signal,and then the effective modal components are found by calculating the values of IMF components and original signals by Hausdorff distance,and the modal components larger than kurtosis threshold are selected.Wavelet filtering is carried out to reconstruct the filtered component and residual component.Simulation results verify that the proposed method is effective.4.In this paper,the acoustic emission signals are decomposed by EMD and VMD through simulation analysis,and the decomposed components are extracted.Through analysis and verification,it is concluded that the state features of the signal can not be accurately extracted by using the EMD method.The decomposed modal components can better reflect the difference of frequency of each acoustic emission signal.Based on the VMD-Wavelet algorithm and cloud model theory,the eigenvalues are extracted and the effectiveness of the method is verified.5.The method of locating microseismic acoustic emission source is analyzed,and the 3D time difference locating algorithm is selected for the location of rock fracture acoustic emission source in this paper.The simulation and verification model is established to obtain the spatial location of fracture point,and the feasibility of the method is verified.