塑性地层宽刃齿破岩机理研究与提速应用

Rock Breaking Mechanism of Wide-bladed Teeth in Plastic Formation and Application of ROP Increase

常规PDC钻头在钻进塑性地层时,存在吃入困难、机械钻速低的问题。为提高复合片吃入地层的能力,对常规PDC钻头布齿情况下的比钻压分布进行理论分析,并提出一种新的宽刃齿齿形。建立了宽刃齿和常规平齿静态压入和切削破岩的有限元模型。模拟结果表明:在同压力下,宽刃齿压入深度比常规平齿深24%~430%,静压入体积也明显增多;在相同工况下,宽刃齿比常规平齿破碎比功更小,更易高效破碎岩石;同时,设计宽刃齿钻头时,前倾角和侧转角不宜过大。基于研究结果开发了新型宽刃齿钻头并在塑性泥岩地层进行了现场应用。应用结果表明,该新型钻头平均机械钻速比同型号常规齿PDC钻头提高515%。研究结果可为解决难钻塑性地层的钻井提速问题提供一种新的思路。

When conventional PDC bits drill into plastic formations,some problems exist such as difficulty in penetration and low ROP.In order to improve the ability of the PDC compact to penetrate the formation,the distribution of specific weight on bit under the condition of conventional PDC teeth arrangement was analyzed theoretically,and a new tooth profile with wide-bladed teeth was proposed.The finite element models of static press-in and rock breaking of wide-bladed teeth and conventional flat teeth were established.The simulation results show that the press-in depth of wide-bladed teeth is 24%~430%deeper than that of conventional flat teeth under the same pressure,and the static press-in volume is increased obviously.Under the same working conditions,the crushing specific work of wide-bladed teeth is smaller than that of conventional flat teeth,and it is easier to break rocks efficiently.At the same time,when designing a wide-bladed tooth bit,the front rake angle and side rake angle should not be too large.Based on the study results,a new type of bit with wide-bladed teeth was developed and applied in plastic mudstone formations.The application results show that the average ROP of the new bit is 515%higher than that of the conventional PDC bit of the same model.The results provide a new idea for increasing ROP in difficult-to-drill plastic formations.