双级PDC钻头井底应力场分析

介绍了双级PDC钻头特征，建立了双级PDC钻头的井底应力场分析模型，给出了相关参数和边界条件以及分析方法，利用有限元方法对双级钻头井底进行三维应力场数值分析得到了井底应力场云图和曲线图，并与常规钻头井底应力场进行了对比。分析和研究认为，双级PDC钻头井底形成了径向应力小、周向应力大的二次应力场，等效应力卸载明显，且总等效应力是常规钻头的85．56％，提高机械钻速的潜力较大。

Analysis of bottom-hole stress field of two-stage PDC bit

The features of two-stage PDC bit were introduced. An analysis model of bottom hale stress fidd of two-stage PBC bit was established, and the correlative parameters, boundary renditions and analysis mettod were provided. The cloud figs and curves of bottom-hole stress fidd were obtained through numerical analysis of 3-D stress fidd by finite dement method, and which were compared with that of common bit. The results show that the secondary bottom hole stress of two-stage PDC bit with smaller radial stress and higher drcumferential stress is devdoped. And the Mises equivalent stress has remarkable unloading effect, and the total equivalent stress is 85.56% of that of common bit. The two-stage PDC2 bit has great potentiality for improving penetration rate.