Electrodes Optimization of an Annular Flow Electromagnetic Measurement System for Drilling Engineering

The early monitoring of downhole overflow can be effectively realized by the downhole annular electromagnetic flow detection system. In order to improve the accuracy of the electromagnetic measurement system of downhole annular flow, it is important to optimize the excitation system and electrodes of this system. This research focuses on the optimization of the electrodes for the electromagnetic measurement system of downhole annular flow, whose excitation system has been optimized. First, the basic principle of electromagnetic measurement of downhole annular flow is analyzed. Then, the influence of different positions of the four-point electrodes on the virtual current distributions is analyzed, and the optimum electrode positions and distributions are introduced. On this basis, the influence of shape and size of the large electrode on virtual current density distribution is analyzed. Based on the theoretical study of the influence of electrode on virtual current density distribution, taking hemispherical electrodes and arc electrodes as examples, this paper optimizes hemispherical electrodes and arc electrodes with different shapes and sizes by using finite element simulation method, and proposes three indexes to evaluate the annular virtual current density distributions when the electrodes of different shapes are used. The optimum parameters of shapes and sizes of the hemisphere electrodes and arc electrodes under specific structures of the downhole annular electromagnetic flow measurement system are obtained. This research has great significance for the optimization of electrodes in the downhole annular electromagnetic flow measurement system, and can also be used as reference for the electrode optimization of the traditional electromagnetic flowmeter.