Abstract: Deep oil and gas resources serve as a strategic alternative for safeguarding China's energy security. Improving the rate of penetration (ROP)in hard rock drilling is a critical challenge faced during deep hydrocarbon explortion. Currently, impact drilling is one of the most effective methods for increasing ROP in hard rock. However, conventional light-load impact drilling cannot meet the urgent engineering demands for higher efficiency. Based on the concept of heavy-load impact rock-breaking, a series of single-tooth impact experiments with and without confining pressure were conducted, and three-dimensional dynamic models were established to simulate the spherical, conical, and bullet-shaped cutter impacts on granite, aiming to investigate the influence of cutter shape, impact energy, and confining pressure on rock breakage under heavy-load impact. Moreover, the specific energy for rock breaking was used as an evaluation indicator for high-efficiency rock-breking intervals. The main findings are as below:(1)Under the confining pressure of 0-60 MPa, as impact energy increases, the fragmentation morphology transitions from a U-shaped crushing pattern to a W-shaped compression-shear failure pattern, and finally evolves into a V-shaped compression-shear-tensile failure mode. (2)Under impact loading, the rock initially experiences high-pressure crushing to form pits, followed by tensile failure induced by stress waves. The overal rock fragmetation follows a pattern of "pit formation under compressive stress+crack generation under tensile + shear spalling". (3)A critical confining pressure threshold exists, around which impact energy and confining pressure alternately dominate rock breakage as the primary controlling factors.

Key words: heavy-load impact, impact rock-breaking, fracture mode, specific energy for rock breaking, critical confining pressure

摘要： 深部油气资源是保障中国油气安全的战略接替,如何提高深部硬岩钻进的机械钻速是深层钻探面临的重要问题。冲击钻进技术是目前解决硬岩钻进机械钻速低的最有效方法之一,但传统轻载冲击提速效果无法满足工程上的迫切提速需求。基于重载冲击破岩理念,开展了室内有/无围压的单齿重载冲击实验,建立了球齿、锥齿和子弹齿冲击花岗岩的三维动力学模型,研究齿形、冲击功和围压等参数对重载冲击下花岗岩破碎效果的影响,并以破岩比功为指标来评价高效破岩区间。研究结果表明:①在0~60 MPa围压下,随着冲击功的增加,破碎形态由U形压碎模式转变为W形压—剪破坏模式,最终演变为V形压—剪—拉破坏模式。②岩石受到冲击载荷时表现为高压压碎成坑,应力波形成拉应力造成拉伸破碎,岩石整体表现为"压应力成坑+拉应力成裂纹+剪切剥离"的冲击破碎规律。③存在一个围压临界值,在该临界值前后冲击功和围压交替成为破岩的主控影响因素。

关键词: 重载冲击, 冲击破岩, 破碎模式, 破岩比功, 围压临界值