Research on Transient Electromagnetic Response of Magnetic Source in Borehole

Abstract

The transient electromagnetic exploration in borehole is a full space geophysical problem. The Gaver‐Stehfeest inverse Laplace transform is used to theoretically calculate the transient electromagnetic response in the receiver loop. And the effects of the parameters of the borehole mud, metal casing, the cement sheath and the formation on electromagnetic logging responses are analyzed. The response curves of different electrical conductivity of the borehole mud indicate that the borehole mud has little effect on the electromagnetic responses. The numerical results of different geometry of the casing pipe show that the inner radius and the thickness of casing have an obvious effect on the logging responses, moreover the abnormality of transient response appears where the casing thickness suddenly increases or decreases. The simulation results of different magnetic permeability of the casing pipe show that it has an important effect on transient response in borehole and the higher the magnetic permeability, the more difficult the electromagnetic signals transmitting through the casing. Results of different parameters of the cement sheath reflect that the high conductive cement sheath can generate large measurement error for low conductive formation. It is also found that the effect of the thickness of the cement sheath can be ignored for high conductive formation.

Three-Dimensional Forward Modeling of Transient Electromagnetic Method Considering Induced Polarization Effect Based on Spectral Element Method

“…The transient electromagnetic method (TEM) is a time-domain electromagnetic exploration method that uses a step wave or pulse current as an excitation source to measure the pure secondary field after the primary field is turned off [1,2]. Due to the broadband nature of the emitted waveforms, which have high resolution, greater detection depth, sensitivity to good conductors, and less susceptibility to terrain limitations, TEM is widely applied in practical fields such as mineral resource exploration [3].…”

Analysis on Mechanical Properties of Instrumented Indentation Tester Frame

“…In this paper, finite element analysis is undertaken to identify the extent of loading deformation of 3D frame model of High-precision instrumented indentation tester [5][6][7][8] which has been developed and realized by us. It is found that the value of frame inclination angle is directly proportional to the working load.…”