Abstract

Among consequences that can be induced by a non-uniform distribution of the stress and other causes during the drilling process is the elliptical shape of the well and consideration of this effect would improve the accuracy of the drilling fluid hydrodynamics prediction. In the present work, the elliptical shape of the annular space is simplified to apply the slot model taking into account the rotation of the inner cylinder. Moreover, the Slot model results are compared with the experimental data, as well as, with the CFD outcomes where a reasonable concordance is observed, especially for low ratios of the major and minor semi-axis. Also, the CFD results are validated with the experimental data from the flow loop setup. We concluded that the increase of the major and minor semi-axis ratio of the elliptical annulus results in a linear increase of the Ostwald-de Waele frictional pressure loss in the laminar regime for all considered rotation speeds of the inner cylinder. In addition, the increase of the eccentricity from 0 to 0.75 has a positive effect where the frictional pressure loss is decreased by almost 28% for all rotation speeds for the elliptical annulus ($\eta =1.2$).

摘要

钻井过程中应力分布不均匀和其他原因可能导致的后果之一是井的椭圆形状，考虑这种影响将提高钻井液流体动力学预测的准确性。在目前的工作中，环形空间的椭圆形状被简化，以应用考虑内圆柱体旋转的槽模型。此外，将 Slot 模型结果与实验数据以及 CFD 结果进行比较，观察到合理的一致性，特别是对于长半轴和短半轴的低比率。此外，CFD 结果通过来自流动回路设置的实验数据进行了验证。我们得出结论，椭圆环的长、短半轴比的增加导致层流状态中 Ostwald-de Waele 摩擦压力损失的线性增加，对于所有考虑的内圆柱体的旋转速度。此外，偏心距从 0 增加到 0.75 具有积极效果，其中对于椭圆环的所有旋转速度，摩擦压力损失降低了近 28%（$\eta =1.2$）。