Zafarian Habiballah, Ameri Mohammad Javad, Dolatyari Alireza
Department of Petroleum Engineering, Amirkabir University of Technology, Tehran, Iran.
Sci Rep. 2024 Mar 11;14(1):5903. doi: 10.1038/s41598-024-56177-0.
PDC drill bits are an important part of drilling engineering, but improper selection or design can lead to decreased performance and increased costs. Then, accurate modeling of rock-bit interaction for Oil/gas well drilling is critical. Although several mathematical models are presented for this purpose, they have not been able to present a comprehensive model for the rock-bit interaction. In-situ stresses in real drilling conditions affect the force required for rock failure. However, the models proposed so far either have not considered the effects of in-situ stresses or have assumed that the rock failure angle in the downhole conditions is equal to the one calculated in the atmospheric conditions. In this work, after reviewing the background of studies conducted on the rock and bit interaction, with an analytical method, stresses applied to the bottom hole element are examined, including stresses resulting from bit and in-situ stresses. Based on the principle of superposition, the total stress imposed on the bottom hole element is calculated to determine the angle and force of rock cutting. Finally, a novel mathematical model of rock-bit interaction in vertical and deviated oil/gas wells drilling by Considering In-Situ Stresses is presented. Also, the study compares the current model to the Nishimatsu and Xin Ling models using data from a southwest field in Iran. The results show that the simplifying assumption made by previous models leads to a significant underestimation of the failure angle and the amount of force required to the rock failure, with reductions of up to 21% and 48%, respectively, in the case of a vertical well. In an inclined well, the current model predicts cutting force at about 0.14 of that predicted by the previous model.
聚晶金刚石复合片（PDC）钻头是钻井工程的重要组成部分，但选择或设计不当会导致性能下降和成本增加。因此，准确模拟石油/天然气井钻井过程中的岩石-钻头相互作用至关重要。尽管为此目的已经提出了几种数学模型，但它们尚未能够给出一个全面的岩石-钻头相互作用模型。实际钻井条件下的地应力会影响岩石破碎所需的力。然而，迄今为止提出的模型要么没有考虑地应力的影响，要么假设井下条件下的岩石破碎角等于在大气条件下计算的角度。在这项工作中，在回顾了关于岩石与钻头相互作用的研究背景后，采用解析方法研究了施加在井底单元上的应力，包括钻头产生的应力和地应力。基于叠加原理，计算施加在井底单元上的总应力，以确定岩石切削的角度和力。最后，提出了一种考虑地应力的垂直和斜井石油/天然气井钻井岩石-钻头相互作用的新型数学模型。此外，该研究使用来自伊朗西南部一个油田的数据，将当前模型与西松模型和辛凌模型进行了比较。结果表明，先前模型所做的简化假设导致对破碎角和岩石破碎所需力的显著低估，在垂直井的情况下，分别低估了高达21%和48%。在斜井中，当前模型预测的切削力约为先前模型预测值的0.14。
