Forward simulation of remaining oil exploration in cross-well by time domain electromagnetic method

Based on electromagnetic field theory, this paper derived the general expressions of time domain responses for cross-well electromagnetic logging. The emission waveform may be chosen as bipolar square wave by calculating the spectrums of three types of transmit signals. And the effects of thickness, magnetic permeability and electrical conductivity of the casing on time domain electromagnetic logging responses were analyzed. The computation results show that the casing change whether thinner or thicker has an obvious effect on the time domain logging responses. The simulation results also indicate the higher the casing electrical conductivity, the lower the response signal amplitude; and the lower the magnetic permeability, the more easy the electromagnetic signals through the casing. Furthermore, the sensitivity analysis of the time domain electromagnetic responses to the formation resistivity indicates that the electromagnetic responses are fairly sensitive to the formation resistivity. This result proved the feasibility and effectiveness of cross-well time domain electromagnetic logging technology applies to the field of oil and gas exploration.