Research on a novel four-electrode and two-group excitation electromagnetic measurement method for downhole bidirectional flow

Abstract Aiming at the difficulty of early overflow monitoring due to the low accuracy of downhole bidirectional flow measurement during drilling, a novel four-electrode and two-group excitation electromagnetic measurement (FTEEM) method for downhole bidirectional flow is proposed. Firstly, the mathematical models of the imaginary current density and magnetic induction intensity in the bidirectional measurement flow path are derived by establishing the theoretical model of the FTEEM sensor. Secondly, the finite element simulation software is used to optimize the four-electrode distribution and the two-group excitation coils structure, and the optimal structural design parameters of the FTEEM sensor structure are obtained. Finally, the bidirectional flow FTEEM principle prototype was built for experimental testing. The experimental results show that when the test range of slurry flow is 7.46–82.65 m 3 h −1 , the maximum single-point flow rate average relative indication errors of the FTEEM principle prototype in the wellbore flow channel and the annulus flow channel are 0.73% and 0.49%, respectively. Compared with the previous bidirectional flow electromagnetic measurement method, the FTEEM method reduces the average relative error of the annulus flow by 0.4%, and at the same time significantly improves the repeatability of the wellbore flow and the annulus flow by up to 19.18% and 79.44%, respectively. The correctness and effectiveness of the FTEEM method for improving the accuracy of bidirectional flow measurement are verified.