Abstract

During drilling of directional and horizontal wells, cutting beds inevitably form in highly deviated and horizontal sections. Because of the centralizer, both concentric and eccentric annuli can exist in both highly deviated and horizontal sections. Existing studies on the helical laminar flow of a non-Newtonian fluid in partially blocked concentric and eccentric annuli are mainly based on numerical models, laboratory experiments, and computational fluid dynamic (CFD) simulations. Directly applying the research results to drilling engineering is difficult. To accurately and conveniently predict the pressure gradient of helical laminar flow with a fixed horizontal cutting bed, this work first presents a new model based on fluid mechanics to compute the pressure loss of a yield-power-law (YPL) flow in partially blocked concentric and eccentric annuli in a laminar helical-flow state. Second, the Fluent software is used to simulate the helical laminar flow of the YPL fluid with a fixed horizontal cutting bed. The existing experimental measurements, mathematical model calculation, and Fluent software simulation results are used to verify the proposed simplified model. The results show that the predicted results of the simplified model agree well with the existing numerical results, existing experimental data, and CFD simulation results; the error is only ±5%. The new simplified model can achieve accurate and convenient prediction of the pressure gradient of a spiral laminar flow in an annulus with a fixed horizontal cutting bed.

摘要

在定向井和水平井钻井过程中，大斜度和水平井段不可避免地会形成切割层。由于扶正器，同心环和偏心环可以存在于大偏心和水平截面中。现有关于非牛顿流体在部分阻塞的同心和偏心环带中螺旋层流的研究主要基于数值模型、实验室实验和计算流体动力学 (CFD) 模拟。将研究成果直接应用于钻井工程是困难的。为了准确方便地预测水平切割床固定的螺旋层流压力梯度，这项工作首先提出了一种基于流体力学的新模型，用于计算层流螺旋流状态下部分阻塞的同心和偏心环中屈服幂律 (YPL) 流的压力损失。其次，使用 Fluent 软件模拟水平切割床固定的 YPL 流体的螺旋层流。现有的实验测量、数学模型计算和 Fluent 软件仿真结果用于验证所提出的简化模型。结果表明，简化模型的预测结果与已有的数值结果、已有的实验数据和CFD模拟结果吻合较好；误差仅为±5%。