磨料射流辅助三翼钻头破岩实验研究

Experimental study of rock breaking by a three wing, abrasive jet assisted drill bit

通过对磨料射流辅助三翼钻头破碎岩石的力学分析,理论上给出了提高钻进速度的依据,利用自行设计的磨料射流实验系统,采用收敛型喷嘴以不同泵压对预制水泥试件进行冲蚀实验,试验研究表明,在泵压及磨料浓度保持不变的情况下,随着冲蚀深度(靶距)的增加,磨料射流的破岩能力先增大后减小,呈抛物线型变化,存在破碎的最优靶距;随着试件硬度的增加,破岩速度减小,冲蚀深度减小,但破岩最优靶距没有变,同一靶距下,破岩速度变小;随着泵压的增大,磨料射流的最优靶距随之增大,最优靶距受喷嘴加速直线段长度的影响;通过致密砂岩的钻进对比实验得出,在同等扭矩及推力条件下,磨料射流辅助钻进的效率可以提高63.4%.

A theoretical basis for improved drilling in rock was developed through a mechanical analysis of rock breaking by a three wing, abrasive, water jet assisted drill bit. Erosion of pre- fabricated cement test samples was performed. An experimental abrasive jet with a convergent nozzle was designed for these tests. Results show that rock breaking ability of the jet first in- creases and then decreases parabolically as a function of erosion depth at a constant pump pres- sure and concentration of abrasive. There appears to be an optimum distance from target to substrate. The rate of fragmentation decreases with increasing specimen hardness. The opti- mum distance from target to substrate does not change, however. The optimum distance does increase with an increase in pump pressure and changes to the accelerating segment length within the nozzle have a strong effect on the optimum length. Drilling efficiency through com- pacted sandstone can be increased by 63.4% when using abrasive jet assisted bits.