多维冲击提高PDC钻头破岩效率的机理研究

在一维冲击辅助破岩技术基础上发展出了更加高效的多维冲击破岩技术,但相应的破岩机理研究却不够深入。为揭示多维冲击提高PDC钻头破岩效率的机理,建立了冲击-切削破岩分析模型,模型将一维和多维冲击作用视为不同角度的单齿冲击问题,通过有限单元法探讨了轴向、扭向和多维冲击作用下岩石的损伤演化和岩屑形成过程,并进一步计算和分析了冲击角度范围为0°~90°的破岩比功,通过现场试验对模拟结果进行了验证。结果表明:一维与多维冲击的岩石破碎机理不同,多维冲击破岩过程同时受到挤压和剪切裂纹的影响;不同冲击速度矢量存在不同的最优冲击角度使破岩比功最低;多维冲击器提速幅度高于一维冲击钻井工具;研究结果有助于传统冲击钻井工具与结构优化的技术升级。

Mechanism of multi-dimensional impact loads applied in increasing therock cutting efficiency of a PDC bit

A multi-directional impact drilling technology was developed on the basis of the unidimensional impact drilling technology.The purpose of the study is to reveal the mechanism of the multi-directional impact load applied in increasing the rock cutting efficiency of a PDC bit.An analysis model of rock cutting was established,and the analysis on the effect of impact loads in different directions was turned into the problem of single cutter impact acting at different angles.The damage evolution process and cuttings formation process under axial,torsional and multi-directional impact loads were studied by the finite element method,and the mechanical specific energy(MSE)with the impact angle range from 0°-90°was calculated.The results show that the mechanism of rock fracture is different under loads in different direction,and the process of rock cutting with multi-directional impact loads is influenced by cracks formed by compression and shear.When the impact angle is 50°,the MSE of rock cutting reaches the minimum,indicating that the cutting efficiency is the highest.The penetration rate of a multi-directional impact drilling tool is higher than that of unidirectional impact drilling tool.The results are helpful to the structural design and performance optimization of impact drilling tools.