The Design of the Coil System in LWD Tools Based on Azimuthal Electromagnetic-Wave Resistivity Combined with Sections

Due to existing azimuthal electromagnetic-wave resistivity, logging-while-drilling tools have low sensitivity for detecting the stratum interface and shallow detection depths; thus the coil system with sectional combination was designed, and assessed using numerical simulation and calculation for the measurement responses of different coil systems by means of theoretical analysis and simulation experiments. At the same time, the effecting regularity of interface position and distance on measurement responses of the coil system was also compared and analyzed. The numerical simulation results showed that the induction signal amplitudes of the designed coil system was higher than that of the existing coil systems, with a detection depth of 1.70 m for the stratum interface. Research results indicated that the innovative coil system could improve the detection sensitivity of logging tools on the interface and depth of formations, and provide valuable guidance for the development of LWD tools based on azimuthal electromagnetic-wave resistivity.