潜孔钻头井底流场数值模拟研究

Numerical simulation on bottom-hole flow field of down-the-hole bit

以QF—Ⅱ型潜孔钻头为原型,充分考虑排屑槽和切削齿对井底流场的影响,建立了与实际相接近的潜孔钻头井底流场模型,采用计算流体力学软件Fluent对钻头井底流场进行了数值模拟研究。分析认为,该潜孔钻头导致井底流场分布不合理的原因在于喷嘴安放位置太靠近钻头边缘。随后对喷嘴位置向钻头中心靠拢后的改型钻头进行了井底流场分析,认为喷嘴位置向钻头中心靠拢,有助于提高井底流场的清岩能力,减小井底流场对井壁的冲蚀破坏程度,为合理进行潜孔钻头的结构设计提供了理论依据。

By taking QF-Ⅱdown-the-hole (DTH) bit as a prototype, and considering the effect of junk slot and cutting-tooth on bottom-hole flow field, a bottom-hole flow field model similar to the actual bit is established and a numerical simulation is carried out on its bottom-hole flow field by using software Fluent. Analysis shows that the reason of improper flow field distribution caused by DTH bit is that the nozzle position is close to the edge of bit. Consequently the flow field is analyzed on the modified bit with its nozzle position adjusted close to the bit center. It is declared that the nozzle position close to the bit center help improve the cuttings-carrying capacity, reduce the erosion and destruction of the wellbore caused by bottom hole flow field.