Study on the coaxial electrode in electrohydraulic shockwave drilling technology

Abstract

In recent years, electrohydraulic shockwave drilling technology has been widely studied to improve the drill rate of deep and ultra-deep wells. However, few studies have been conducted on coaxial electrodes that are more suitable for drilling. Therefore, it is of great significance to study the discharge characteristics of coaxial electrodes and the influence of various factors on their discharge effects. Firstly, the electric field models of the coaxial electrode were established and simulated using the CST software. The results showed that the electrical breakdown occur randomly on the circular edge of the coaxial electrode. Abnormal electrical breakdown may occur at the junction of anode and insulation layer, which may damage the insulation layer, and this has also been verified in the experiments. Secondly, the influence of various parameters on the discharge effect was further studied based on the model. The results showed that higher voltage and liquid dielectric constant can effectively enhance the electrical breakdown ability. Larger or smaller electrode spacing and insulation concave depth can reduce the discharge effect or more damage the insulating layer. A smaller anode diameter has a stronger electrical breakdown ability, but the final shock wave becomes smaller. Finally, electrical breakdown experiment and rock breaking experiment were conducted to verify the simulation results. In summary, this study conducted in-depth research on coaxial electrodes through CST electric field simulation and experiments, which provided a basis for coaxial electrode design and can effectively promote the practical application of electrohydraulic shockwave technology.