Eddy current test has been widely used in many fields because of its simplicity and robustness. In this paper, numerical simulations based on the finite-difference time-domain method were carried out to validate if the eddy current coil can effectively be used in the logging while drilling system. The simulation results showed that the impedance of the eddy current coil is a function of conductivity of the surrounding media. The formation conductivity is strongly dependent on the concentration of hydrocarbons, so different formation layers can be distinguished by measuring coil impedance. Different source frequencies were applied, and it was found that this method works well in frequency range from 100 MHz to 1 GHz. The investigation depth was studied in this paper, and a 3-layer formation model was simulated in this paper. The results showed that this novel method could be effectively used in a well logging system.
"Investigation of a Conductivity Logging Tool Based on Single Coil Impedance Measurement Using FDTD Method," Progress In Electromagnetics Research M,
Vol. 39, 171-180, 2014. doi:10.2528/PIERM14091905
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