Wang Changhao, Li Shaojie, Li You, Hou Lidong, Bai Jinsong, Feng Qianwen, Liu Zhaoyi
National Key Laboratory of Multi-Resource Collaborative Green Exploitation of Continental Shale Oil, Northeast Petroleum University, Daqing, 163318, China.
Liaohe Oilfield Oil Production Technology Research Institute, Panjin, 124010, China.
Sci Rep. 2024 Jul 16;14(1):16345. doi: 10.1038/s41598-024-67521-9.
During rock drilling, a drill bit will wear as it breaks the rock. However, there is no uniform grading standard for rock abrasiveness. To solve this problem, the wear mechanisms of a polycrystalline diamond compact (PDC) bit and the formation it is drilling into are analyzed in depth, and an abrasiveness evaluation method based on the fractal dimension of the rock surface topography is established. Initially, a three-dimensional digital model is generated from a scanning electron microscope image of the rock after drilling; next, an evaluation of the irregularities on the rock surface is performed using an adapted Weierstrass-Mandelbrot (W-M) function to ascertain the fractal dimensionality. Then, the microcontact characteristics of the contact surface between the formation and the PDC bit are analyzed, and the distribution of the microconvex contact points of the two-body friction pair in a region is obtained. Because the sliding friction between the drill bit and the rock produces a large amount of heat, according to the contact area formula of the friction surface and heat conduction theory, the temperature rise and overall temperature distribution of the formation and PDC bit under the condition of sliding friction are revealed, and the real contact area between the formation and the drill bit within a certain temperature range is obtained. Finally, the evaluation index of rock abrasiveness under sliding conditions is established by adopting the wear weight loss of the rock cutting tool per unit volume as the index of rock abrasiveness, and the model is verified by a microdrilling experiment. The research in this paper is highly important for improving the rock-breaking efficiency and bit service life during drilling.
在岩石钻进过程中，钻头在破碎岩石时会发生磨损。然而，目前尚无统一的岩石研磨性分级标准。为解决这一问题，深入分析了聚晶金刚石复合片（PDC）钻头及其钻进地层的磨损机制，并建立了基于岩石表面形貌分形维数的研磨性评价方法。首先，根据钻进后岩石的扫描电子显微镜图像生成三维数字模型；其次，采用改进的魏尔斯特拉斯-曼德勃罗（W-M）函数对岩石表面的不规则性进行评价，以确定分形维数。然后，分析地层与PDC钻头接触表面的微观接触特性，得到两体摩擦副在某一区域内微凸接触点的分布情况。由于钻头与岩石之间的滑动摩擦会产生大量热量，根据摩擦表面的接触面积公式和热传导理论，揭示了滑动摩擦条件下地层与PDC钻头的温度升高及整体温度分布情况，并得到了一定温度范围内地层与钻头之间的真实接触面积。最后，以岩石切削刀具单位体积的磨损失重作为岩石研磨性指标，建立了滑动条件下岩石研磨性评价指标，并通过微钻实验对该模型进行了验证。本文的研究对于提高钻进过程中的破岩效率和钻头使用寿命具有重要意义。
