利用井底应力场研究双级钻头导扩眼直径比

Research on diameter ratio of pilot to enlarger of two-stage bits using bottom-hole stress field

为研究双级钻头导扩眼直径比,应用双级钻头的井底应力场分析模型、开挖方法、分析过程及分析选项,对Φ190.5mm×Φ311mm、Φ215.9mm×Φ311mm和Φ241.3mm×Φ311mm3种双级钻头进行井底三维应力场开挖分析,得到了井底应力场分布曲线,井底应力场曲线显示:Φ241.3mm×Φ311mm双级钻头的径向应力释放较充分,有利于提高机械钻速;Φ215.9mm×Φ311mm双级钻头径向和周向两应力差减小,但仍有较大提高机械钻速的潜力;Φ190.5mm×Φ311mm双级钻头的径向和周向两应力差很小,其提高机械钻速的潜力较小;双级钻头的导眼体与钻头的直径比存在最优值,最优直径比为0.7～0.8。

The excavation analysis of the bottom-hole three dimension stress field excavation is carried out on the two-stage bits of three diameter ratio 190.5 mm×311 mm, 215.9 mm×311 mm, and 241.3 mm×311 mm in order to research the diameter ratio of pilot to enlarger. The analysis model, excavating methods, analyzing process, and analysis options of the bottom-hole stress field are applied during the research process. The distribution curve of the bottom-hole stress field is obtained, which shows that the radial stress of the 241.3 mm×311 mm bit is more completely released and is favorable for increasing the penetration speed. The difference between radial stress and circumferential stress of the 215.9 mm×311 mm bit gets smaller but it still has great potential to improve its penetration rate. The difference of radial stress and circumferential stress of the 190.5 mm×311 mm bit is small and the potential to increase penetration speed. Its optimum diameter ratio of pilot to enlarger is 0.7～0.8.