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.
2. Wait, J. R., "Complex resistivity of the earth," Progress In Electromagnetics Research, Vol. 1, 1-173, 1989.
doi:10.1016/B978-0-444-01490-0.50006-4
3. Hasar, U. C., "Permittivity determination of fresh cement-based materials by an open-ended waveguide probe using amplitude-only measurements," Progress In Electromagnetics Research, Vol. 97, 27-43, 2009.
doi:10.2528/PIER09071409
4. Lee, K. Y., B.-K. Chung, Z. Abbas, K. Y. You, and E. M. Cheng, "Amplitude-only measurements of a dual open ended coaxial sensor system for determination of complex permittivity of materials," Progress In Electromagnetics Research M, Vol. 28, 27-39, 2013.
doi:10.2528/PIERM12082906
5. Wang, B., K. Li, F. Kong, and S. Sheng, "Complex permittivity logging tool excited by transient signal for MWD/LWD," Progress In Electromagnetics Research M, Vol. 32, 95-113, 2013.
doi:10.2528/PIERM13041105
6. Anderson, B. I., Modeling and Inversion Methods for the Interpretation of Resistivity Logging Tool Response, Delft University Press, Delft, 2001.
7. Ellis, D. V. and J. M. Singer, Well Logging for Earth Scientists, Springer, Dordrecht, 2007.
doi:10.1007/978-1-4020-4602-5
8. Lee, H. O., et al., "Numerical modeling of eccentered LWD borehole sensors in dipping and fully anisotropic Earth formations," IEEE Transactions on Geoscience and Remote Sensing, Vol. 50, 727-735, 2012.
doi:10.1109/TGRS.2011.2162736
9. Tianxia, Z., M. Gerald, H. John, and C. G. Jaideva, "A novel technique to compute impedance of an arbitrarily oriented coil antenna for well logging applications," 2012 IEEE Antennas and Propagation Society International Symposium (APSURSI), Vol. 39, 2829-2838, 2012.
10. Theodoulidis, T. P., T. D. Tsiboukis, and E. E. Kriezis, "Analytical solutions in Eddy current testing of layered metals with continuous conductivity profiles," IEEE Transactions on Magnetics, Vol. 31, 2254-2260, 1995.
doi:10.1109/20.376236
11. Uzal, E., J. C. Moulder, S. Mitra, and J. H. Rose, "Impedance of coils over layered metals with continuity variable conductivity and permeability: Theory and experiment," Journal of Applied Physics, Vol. 74, 2076-2089, 1993.
doi:10.1063/1.354773
12. Uzal, E. and J. H. Rose, "The impedance of eddy current probes above layered metals whose conductivity and permeability vary continuously," IEEE Transactions on Magnetics, Vol. 29, 1869-1873, 1993.
doi:10.1109/20.250771
13. Uzal, E., M. O. Kaya, and I. Zkol, "Impedance of a cylindrical coil over an infinite metallic halfspace with shallow surface features," Journal of Applied Physics, Vol. 86, 2311-2317, 1999.
doi:10.1063/1.371047
14. Theodoulidis, T. P. and J. R. Bowler, "Impedance of an induction coil at the opening of a borehole in a conductor," Journal of Applied Physics, Vol. 103, 024905, 2008.
doi:10.1063/1.2827459
15. Trltzsch, U., F. Wendler, and Kanoun, "Simplified analytical inductance model for a single turn eddy current sensor," Sensors and Actuators A: Physical, Vol. 191, 11-21, 2013.
doi:10.1016/j.sna.2012.11.024
16. Vasic, D., V. Bilas, and D. Ambrus, "Validation of a coil impedance model for simultaneous measurement of electromagnetic properties and inner diameter of a conductive tube," IEEE Transactions on Instrumentation and Measurement, Vol. 55, 337-342, 2006.
doi:10.1109/TIM.2005.861244
17. Vasic, D., V. Bilas, and B. snajder, "Analytical modelling in low-frequency electromagnetic measurements of steel casing properties," NDT & E International, Vol. 40, 103-111, 2007.
doi:10.1016/j.ndteint.2006.10.006
18. Hue, Y. K., F. L. Teixeira, L. E. S. Martin, and M. Bittar, "Modeling of EM logging tools in arbitrary 3-D borehole geometries using PML-FDTD," IEEE Geoscience and Remote Sensing Letters, Vol. 2, 78-81, 2005.
doi:10.1109/LGRS.2004.840637
19. Taflove, A. and S. C. Hagness, Computational Electrodynamics: The Finite-difference Time-domain Method, Artech House, Boston, 2000.
20. Luebbers, R., L. Chen, T. Uno, and S. Adachi, "FDTD calculation of radiation patterns, impedance, and gain for a monopole antenna on a conducting box," IEEE Transactions on Antennas and Propagation, Vol. 40, 1577-1583, 1992.
doi:10.1109/8.204752
21. TerMan, F. E., Radio Engineers’ Handbook, McGraw-Hill, London, 1950.
22. De Mulder, B., K. Van Renterghem, E. De Backer, P. Suanet, and J. Vandewege, "Java-enabled low cost RF vector network analyzer," The 3rd International IEEE-NEWCAS Conference, 377-380, 2005.