Simulating cross-hole electromagnetic field 's response with metal casing using Green 's functions of radial-layered medium and integral equations

Key words:  cross-hole electromagnetic field  metal casing  Green 's functions  integral equations

Abstract:

The recursive matrix method for computing Green 's functions of radial-layered medium is combined with the BCGS algorithm for integral equations to simulate the response of axial symmetric 2-D cross-hole electromagnetic fields with metal casing. The results show that the intensity of the cross-hole electromagnetic signal is weakened by the metal casing, and the degree of attenuation in the signal will rise with the frequency increasing. The influence of the metal casing on the amplitude of magnetic induction intensity is approximately constant and is irrelevant to formation 's conductivity. The metal casing also changes the phase of the cross-hole magnetic induction intensity, which leads to the phenomenon of ‘shift’ on both the real part and the imaginary part of the cross-hole magnetic induction intensity. The influence of casing can be neglected when its conductivity is small. There is a fast change on the magnetic induction intensity when the casing 's conductivity reaches a critical value. The value is related to frequency:the higher the frequency, the smaller the critical value.