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3D Cutting Force Model of a Stinger PDC Cutter: Considering Confining Pressure and the Thermal Stress
Rock Mechanics and Rock Engineering ( IF 6.2 ) Pub Date : 2021-06-10 , DOI: 10.1007/s00603-021-02494-z
Chao Xiong , Zhongwei Huang , Huaizhong Shi , Ruiyue Yang , Xianwei Dai , Wenhao He

Cutting force prediction of the Stinger PDC cutter is a critically important work for the hybrid PDC bit design, which will directly affect the working stability and rock-breaking efficiency of drill bits. Thermal stress caused by drilling fluid cooling high temperature rock has significant influence on cutting force in geothermal drilling. However, to our best knowledge, the investigation of thermal stress in cutting force models for Stinger PDC is still limited. This paper presents a 3D cutting force analytical model of a Stinger PDC cutter based on the rock stress analysis, which considers the comprehensive influences of in-situ stress, hydrostatic pressure, and thermal stress. The model accuracy is validated by experimental data with less than 7% error in atmosphere condition. The simulation results show that a spherical shape stress concentration zone around the Stinger PDC cutter tip is formed, where the rock is mainly subjected to tensile stress. With the increase of in-situ stress and hydrostatic pressure, the cutting force increases linearly, but the hydrostatic pressure has smaller influence on the cutting force than in-situ stress. The induced thermal stress belongs to tensile stress, which can sharply decrease the cutting force, and the amplitude of cutting force reduction reaches 74% at cutting depth of 1 mm when the formation temperature is 300 °C. In addition, the cutting force also reduces with the increase of the formation temperature and the heat transfer coefficient. The key findings of the work will be expected to help design the hybrid PDC bit used in geothermal drilling.



中文翻译:

Stinger PDC 刀具的 3D 切削力模型:考虑围压和热应力

Stinger PDC刀具的切削力预测是混合PDC钻头设计的一项至关重要的工作,将直接影响钻头的工作稳定性和破岩效率。钻井液冷却高温岩石引起的热应力对地热钻井中的切削力有显着影响。然而,据我们所知,Stinger PDC 切削力模型中的热应力研究仍然有限。本文提出了基于岩石应力分析的 Stinger PDC 刀具的 3D 切削力分析模型,该模型考虑了地应力、静水压力和热应力的综合影响。模型精度得到了实验数据的验证,大气条件下误差小于7%。模拟结果表明,在 Stinger PDC 刀尖周围形成了球形应力集中区,岩石主要受拉应力作用。随着原位应力和静水压力的增加,切削力线性增加,但静水压力对切削力的影响小于原位应力。诱导热应力属于拉应力,可使切削力急剧下降,当地层温度为300℃时,切削深度为1mm时,切削力下降幅度达74%。此外,切削力也随着地层温度和传热系数的升高而降低。预计这项工作的主要发现将有助于设计用于地热钻井的混合 PDC 钻头。

更新日期:2021-06-11
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