超深层井底应力环境下PDC单齿破岩机理研究

Research on Single-tooth PDC Rock Breaking Mechanism at Ultra-deep Bottomhole Stress

为了提高深部地层钻井机械钻速,结合高温高压条件下岩石的特性进行了室内试验,研究了超深层井底应力环境下PDC钻头切削齿破岩机理和PDC切削齿几何参数(前倾角)对钻进效果的影响,同时进行高温高压敏感性分析并对作业参数进行了优选。研究结果表明:在高温高压条件下前倾角对岩石破碎规律的影响与常温常压基本一致,前倾角20°左右时破岩效果最好;在高围压环境下,钻进速度随着温度的升高而增加,当钻压较小时,钻进速度增大趋势较缓,当钻压超过某一值后,钻进速度随温度的升高显著增加;高温高压条件下岩石的破碎规律与常温常压下基本相同,钻进速度随钻压及转速的增大而增加,但是增加幅度变小。研究结果可为钻头结构和钻进参数的进一步优化设计提供一定的指导。

In order to improve the rate of penetration(ROP)into deep formations,laboratory tests were carried out on how a PDC bit breaks rock and how the geometric parameters of the PDC teeth affect the ROP at a deep bottomhole at high temperature,pressure and stress,and finally sensitive factors were analyzed and operating parameters were selected.The results show that,at high temperature and high pressure,the effect of forward inclination on breaking rock is almost the same as at normal temperature and pressure;the breaking effect is best when the forward inclination is about 20°;at high confining pressure,the ROP increases with temperature;when the weight on bit(WOB)is low,the increase of the ROP becomes slow;when the WOB exceeds a certain value,the ROP increases significantly with temperature;the rock breaking law at high temperature and high pressure is almost the same as at normal temperature and pressure,and the ROP increases with the WOB and the rotary speed,but the increase tends to be slow.The research results can provide some guidance for optimization of drill bit structure and drilling parameters.