Numerical modeling of the signal transmission by cables and electromagnetic coupling for logging while drilling

Abstract

Lack of efficiency in transmitting logging signals has long been one of the crucial problems for the development of logging while drilling. This study aims to address this issue by using the advanced scheme for logging while drilling signal transmission, proposed by NovatekTM. The main points of the study focus on electromagnetic coupling between two adjacent pipes and the signal transmission in coaxial cables imbedded in drilling pipes. According to the axial symmetry of the electromagnetic coupling structure, the numerical mode matching is used to establish the numerical model for it. Through simulation analysis which is based on the numerical modeling of the electromagnetic coupling structure, we analyze how various parameters of the structure influence the coupling, obtain some significant conclusions, and optimize the coupling structure. The conclusions can be used to guide optimization design of coupling structure between the drill-pipe for signal transmission in logging while drilling. In addition, the rectangular transmission line whose characteristic impedance is 50 Ω is designed for the cable imbedded in the drill pipe, and the attenuation is calculated. Finally, simulation and experiment are performed for one unit of the pipeline. The results are in agreement with each other, thereby showing the good transmission performance.