Research On Data Compression And Reconstruction Method For Wellbore 3D Detection

Three-dimensional wellbore inspection can be achieved by using the advantages of noncontact and high resolution of transient electromagnetic method to explore oil and gas well media and detect casing damage in complex well conditions.In this paper,in order to solve the problems of large signal volume and difficult transmission of high precision transient electromagnetic detection array 3D inspection system,a method of compressed reconstruction of wellbore 3D inspection data is studied based on the transient electromagnetic method wellbore 3D inspection model and compressed sensing technology.Firstly,the excitation magnetic field distribution of the transient electromagnetic method is introduced,and the magnetic field reception of different arrangement structures is analyzed.The COMSOL finite element simulation software is used to establish a model to simulate the downhole magnetic field distribution,and the wellbore 3D detection system based on the transient electromagnetic array is designed.On this basis,a compression-aware downhole signal compression reconstruction method based on compression sensing is proposed for the signal transmission and storage pressure existing in the wellbore 3D detection array system.The method uses empirical modal decomposition(EMD)to correct the effect of transient EM logging signal baseline drift and simplify the signal frequency components,and then uses compressive sensing technique to compress the transient EM array signal into a small number of measurements,and then uses reconstruction algorithm to recover the original signal after transmitting the measurements to the surface system.To further improve the compression efficiency,a two-dimensional reconstruction method based on compression perception is designed for the characteristics of the transient electromagnetic array signal,which can effectively improve the compression and reconstruction efficiency of the signal.In addition,according to the arrangement of detection arrays in 3D detection system,comparing the effect of different combinations of sparse and measurement methods,the compression reconstruction methods applicable to uniform linear and uniform toroidal detection systems are designed and obtained respectively,which have good reconstruction performance.Finally,based on LabVIEW platform and MATLAB computational software,the software of compressive reconstruction method for 3D inspection data of wellbore was developed and field experiments were carried out.The experimental results show that the 2D transient electromagnetic array signal reconstruction method based on compression perception proposed in this paper can effectively relieve the signal transmission and storage pressure and further improve the compression efficiency of the downhole array signal;the optimal compression reconstruction method for uniform linear and uniform annular distribution arrays shows good compression reconstruction effect in the corresponding wellbore 3D detection system and can solve the array transient electromagnetic data storage and transmission problems of the arraybased transient electromagnetic detection system.