石油钻井过程中,硬岩破碎的成本、环保及效率问题亟待解决。高压电脉冲钻井技术以其破岩高效性、绿色环保性、钻具磨损低及时间成本低等优势而成为目前新型钻井技术的研究热点。为进一步推动高压电脉冲破碎非均质硬岩机理研究,利用Particle Flow Code (PFC)软件及泰森多边形建立了不同非均质性指数的硬岩模型、单对电极破碎非均质硬岩的多物理场耦合二维电击穿数值模型,开展了电极结构、脉冲放电电压和岩石非均质性对高压电脉冲破碎非均质硬岩机理的影响研究。研究表明:等离子通道的发展倾向于在局部介电强度薄弱处萌生,最终引导等离子通道的放电轨迹,与岩石本身的非均质性密不可分;电极端部会产生尖端放电作用,该处产生电场的局部集中强化作用可大大提高破岩效果,但其对等离子体通道的生长轨迹影响较小;硬岩的非均质性指数越大,在高压电脉冲作用下越易发生电击穿,硬岩的破碎程度与穿透深度都显著提高;脉冲放电电压值越大,电损伤越易向硬岩深处累积发展,越有利于破碎硬岩。该研究结果可为深部地层中复杂井况下的电脉冲破岩技术应用提供理论和技术支持。
In oil drilling operations, the challenges of cost, environmental protection, and efficiency in hard rock fragmentation urgently need to be addressed. High-voltage electric pulse drilling, with its high efficiency, eco-friendliness, low tool wear, and time-cost advantages in rock fragmentation, has become a research hotspot. To advance the understanding of the mechanism of high-voltage electric pulse fragmentation of heterogeneous hard rock, models of hard rock with different heterogeneity indices were developed using Particle Flow Code (PFC) software and Voronoi diagram. Additionally, a 2D electro-breakdown numerical model for single-pair electrodes fragmenting heterogeneous hard rock was established. The study focused on the effects of electrode structure, pulse discharge voltage, and rock heterogeneity on the high-voltage electric pulse heterogeneous rock fragmentation mechanism. The study shows that the plasma channel tends to initiate at local dielectric weak points, guiding its discharge path, closely related to the rock′s heterogeneity. The electrode tip′s discharge enhances the local electric field, improving rock fragmentation effect but minimally affecting plasma channel growth. Greater heterogeneity indices make hard rock more prone to electro-breakdown, significantly increasing fragmentation and penetration depth. Higher pulse discharge voltages promote deeper electric damage accumulation, favoring hard rock fragmentation. The study offers theoretical and technical support for applying electric pulse rock fragmentation in complex deep-formation well conditions.
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