The performance evaluation of MWD logging tools using magnetic and electric dipoles by numerical simulations

Traditional measurement-while drilling (MWD) logging tools use magnetic dipoles (coils) as transmitting and receiving antennas and operate at a fixed frequency. In this paper, a new MWD tool using electrical dipoles and using pulses as transmitting signals is investigated and its performance is compared to the coil-type MWD tool in the same formation using a numerical simulation technique. The performances of these two different tools are compared both in the time domain and in the frequency domain. A time-domain transmission-line-matrix (TLM) method is used to perform the analysis. It is shown that a pulsed electric-dipole type MWD tool is superior to a coil-type MWD tool in detection of formation boundaries in all the tested cases. It is further suggested that an MWD tool using electric dipole antennas may be more sensitive in practical applications.