屈服幂律流体螺旋层流流动压降简化模型#

钻井过程中环空流动压降的准确预测能够为井底动压力的精确控制提供理论依据,避免出现因井底压力控制不当而导致的溢流、井漏乃至井喷等井下复杂情况。当前国内外学者针对不同钻井条件下的流动压降开展过大量的理论和实验研究,但现有研究成果很难实现螺旋层流流动压降的准确便捷预测。为了实现螺旋层流流动压降的准确便捷预测,在基于数值模型预测结果的基础上,建立屈服幂律流体螺旋层流流动压降预测简化模型,并利用仿真模拟和室内实验结果对简化模型的有效性进行了验证。结果表明:屈服幂律流体同心环空螺旋层流流动压降简化模型预测结果与实验结果和仿真模拟均吻合较好,简化模型预测误差仅为±5%。

Simplified Modeling of Laminar Helical Flow in Concentric Annulus with YPL Fluid

Accurately predicting pressure gradient with inner pipe rotation in concentric or eccentric annuli can provide theoretical foundation to evaluate equivalent mud weight for avoiding donwhole problems caused by overlarge donwhole pressure, such as: gas kick, lost circulation, even blowout. Nowadays, a lot of studies were carried out on basis of theoretical and experimental researches, however, to the best of our knowledge, no simplified model has been reported to predicting pressure gradient in concentric annuli with inner pipe rotation for yield-power-law (YPL) fluids. A Simplified modeling of laminar helical flow in concentric annulus with YPL fluids has been established on basis of numerical results. In addition, the validation of simplified model has been investigated by comparing results with computational fluid dynamic (CFD) simulations and experimental studies. Predictions of simplified model shown good agreement with CFD and experimental results only within ±5% error bars for power-law and YPL fluids in eccentric annuli.