亚弹速钢质颗粒流冲击作用下岩石内部微观损伤机理与定量分析

Drilling practice in field indicates that particle impact drilling is a promising technology to increase the drilling rate of penetration (ROP) by 2~4 times in hard, extra-hard and strong abrasive formations. When particle flows with high velocity impact the rock, besides the macroscopic breaking pits in the surface, the impact stress wave would propagate within the rock and cause microscopic damages. Such kind of damages in the internal structure can change the physical and mechanical properties of the rock macroscopically and improve its drill ability, which helps to increase the ROP of particle impact drilling. This program will systematically investigate the responses of the internal microstructure of the rock under the impacts of steel-particle flow with sub-missile velocity (25~500m/s) by physical simulation, numerical modeling and theoretical analysis. The formation and evolution of damages in the internal microstructure under the impacts of particle flow would be analyzed experimentally by comparing the changes in the microstructure and the physical and mechanical properties. A dynamic numerical modeling method of the stress field within the rock under the impacts of steel-particle flow with sub-missile velocity would be developed, and the superposition and propagation of stress wave caused by the impacts of particle flow would be quantitatively analyzed. Based on the results of experiments and numerical modeling, the impact breaking of particle flow, the stress wave, and the internal micro-damages of the rock will be integrated to theoretically analyze the mechanism of the internal micro-damages due to the impacts of steel-particle flow with sub-missile velocity and develop a quantitative evaluation model, which would provide theoretical supports for the further development of particle impact drilling, and fill the scientific research gaps in this field at home and abroad .

实践证明，粒子冲击钻井有望突破硬、极硬与强研磨性地层机械钻速低的难题，将钻速提高2~4倍，极具发展潜力。刚性颗粒流高速冲击岩石除在表面产生宏观破碎坑外，冲击应力波还会使岩石内部产生微观损伤，导致岩石物理力学性质改变，进而改善岩石可钻性，提高钻进速度。本课题拟通过物理模拟、数值模拟和理论分析相结合的方法，深入研究亚弹速（25~500m/s）钢质颗粒流作用下岩石内部微观结构的响应特征。通过对比分析颗粒流冲击前后岩石微观结构和宏观物理力学性质的变化，揭示颗粒流冲击作用下岩石内部微观损伤的形成与演化过程；建立亚弹速钢质颗粒流冲击岩石的应力场动态模拟方法，分析颗粒流冲击应力波的叠加与传播规律；综合物理模拟与数值模拟结果，将颗粒流冲击破碎、冲击应力波传播及岩石内部微观损伤相结合，揭示亚弹速钢质颗粒流作用下岩石内部微观损伤机制，建立定量分析模型，为粒子冲击钻井技术提供理论支撑，填补该领域国内外研究空白。

破岩效率低、机械钻速慢是制约深层超深层油气钻探的关键技术瓶颈之一。粒子射流钻井技术有望在硬、极硬与强研磨性地层提高机械钻速2-4倍，为超深层油气安全高效开发提供新思路。但目前对钢质粒子射流连续冲击破岩机理认识尚不完善，制约了粒子冲击钻井技术的发展。本项目采用理论分析、实验测试和数值模拟相结合的方法，系统研究了钢质粒子流冲击作用下岩石的损伤破碎机制及其定量评价。在实验方面，开展了不同粒子射流工作参数下的冲击破岩实验，揭示了钢质粒子射流参数对破岩效率的影响规律，优选了粒子射流钻井工作参数；对粒子射流冲击前后岩石样品开展了一系列宏观-微观物理力学性质测试，定量刻画了钢质粒子射流在岩石内形成损伤区的范围，建立了损伤区内岩石物理力学性质的变化规律。在数值模拟方面，采用SPH+FEM方法构建了钢质粒子射流冲击破岩的动态数值模拟方法，揭示了钢质粒子流冲击岩石的应力波传播规律，明确了裂隙参数对冲击应力波传播和岩石损伤的影响。综合实验和数值结果，结合理论分析，构建了岩石内粒子冲击应力波传播的理论模型，提出了钢质粒子流冲击岩石的损伤区模型和主控机制。该项目研究成果为PID钻头优化设计提供了理论支撑，有力推动了粒子射流冲击钻井技术的发展。