Study On Forward Modeling And Inversion Imaging Of Crosshole Electromagnetic Wave Detection

In recent decades,crosshole electromagnetic wave detection technology has been greatly developed.Compared with some traditional electromagnetic logging methods,crosshole electromagnetic wave detection can overcome its shortcomings such as being only sensitive to the borehole range,so its application range is also relatively wide.This paper leads to two issues of forward simulation and inversion imaging of crosswell electromagnetic waves from the problem of crosshole electromagnetic wave detection.In this paper,the method used for forward simulation is the time-domain finite difference method,and the method used for inversion imaging is the full waveform inversion method.The finite-difference time-domain method is widely used in the field of electromagnetic computing,and its numerical simulation of electromagnetic waves is relatively accurate;The full-waveform inversion method has been applied earlier in the field of seismic exploration.It has also been used in a wide range of applications.Its imaging effect is better,and it can accurately give the size and position of the abnormal body.In this paper,the absorption boundary conditions used in forward simulation calculations are perfectly matched layer absorption boundary conditions,and the data used in inversion imaging are synthetic data.In the forward simulation of crosshole electromagnetic wave detection,this paper uses the time-domain finite difference method combined with the perfectly matched layer absorption boundary conditions to carry out forward simulation of crosshole electromagnetic wave detection and obtain the corresponding wavefield diagram,waveform array and the received signals at each receiving end Signal;This paper analyzes the corresponding wave field diagram and the signal received at the receiving end,and analyzes the influence of the change of the dielectric constant of the medium on the wave speed of the electromagnetic wave in the medium and the change of the medium conductivity on the attenuation of the amplitude(energy)of the electromagnetic wave in the medium.This paper sets up a model with multiple anomalies in multiple strata for forward simulation.By observing its corresponding wavefield diagram and receiving array,the effects of dielectric permittivity and conductivity on wave reflection and transmission are analyzed.The attenuation of waves in the complex situation of underground media is studied.In the full-waveform inversion imaging,this paper carried out the work of separate inversion imaging of conductivity,separate inversion imaging of dielectric constant,simultaneous inversion imaging of dielectric constant and conductivity,etc.In this paper,by changing the distribution settings of electrical parameters of the model several models were studied and the resolution,imaging,and anomaly identification of conductivity and permittivity inversion imaging were studied accordingly.In this paper,transmission and reception were studied by changing the arrangement of transmission and reception the influence of the arrangement method on the conductivity and dielectric constant inversion imaging results,and the possible causes of these effects are analyzed;At the end of this paper,the problem of simultaneous inversion of the dielectric constant and conductivity is studied,and the comparison and discussion of different underground.In the case of a medium,the difference between the dielectric constant and the conductivity imaging results obtained by the simultaneous inversion of the dielectric constant and the conductivity.