大直径引射器式反循环钻头结构设计及数值模拟

Structural design and numerical simulation on large-diameter reverse circulation drill bits with ejectors

针对油气勘探开发特点的要求,将贯通式潜孔锤反循环钻井技术应用于大直径井眼段、复杂地层深井段的油气勘探开发领域,并根据多喷嘴引射器原理,设计一种外径为660 mm的新型大直径引射器式反循环钻头,并进行计算流体动力学(CFD)分析以及野外钻井试验。研究结果表明:该新型大直径反循环钻头结构设计合理,所形成的一、二级引射结构均对反循环形成效果和抽吸能力有良好促进作用,最高钻进效率可达6.0 m/h,平均钻进效率为4.5 m/h,并将井底破碎下的不同颗粒粒度的岩渣屑及地层流体抽吸进入钻头内部形成稳定反循环携带至地表,孔底无沉渣,并且外环间隙无岩渣屑泄漏现象。

In order to apply the reverse circulation drilling technology with hollow through DTH air hammer to the exploration and production of oil and gas resource by means of large diameter wells or deep wells in complicated stratum, a new 660 mm diameter reverse circulation drill bit with ejectors was innovatively designed on the basis of ejecting theory with multi-nozzles according to the requirements for exploring and producing oil and gas resources, and the detailed computational fluid dynamics（CFD） analysis and subsequent field drilling tests were also completed. The results show that the ejecting structures of both the first ejector and the second ejector on new large-diameter reverse circulation drill bit have a positive influence on the formation of reverse circulation and the improvement of suction capability. The optimum penetration rate of drill bit can reach 6.0 m/h, and the average penetration rate is 4.5 m/h. The cuttings with various particle sizes and the fluid reserved in strata can be duly discharged from the bottom of drilling wells to earth surface, and no extra sediments exist in the bottom of drilling wells. Furthermore, no cuttings are leaked from the annular space between borehole wall and the drill string.