泡沫钻井环空岩屑浓度影响因素分析

An analysis of the influencing factors on the annular cuttings concentration during foam drilling

为了准确地计算泡沫钻井环空岩屑浓度,利用多相流体力学方法计算了该值,并着重分析和讨论了岩屑直径、岩屑形状和注液流量对其的影响,建立了泡沫钻井过程中泡沫、岩屑在环空中流动的数学模型,还采用修正Simple方法对该模型进行了数值求解。计算结果表明:①岩屑颗粒直径越大,环空岩屑浓度越大;②岩屑形状越不规则,环空岩屑浓度越低;③在浅井段,环空岩屑浓度随注液流量的增大而增大,而在深井段,环空岩屑浓度随注液流量的增大而增大;④该数学模型考虑了加速度和泡沫与岩屑之间相对滑动的影响,预测的井底压力更接近于实验数据,计算的环空岩屑浓度更准确。

The method of multiphase hydrodynamics was employed to calculate more accurately the annular cuttings concentration during the foam drilling, on which the influences of cuttings sizes, cuttings shapes, and injection liquid rate were mainly analyzed and discussed in this paper. Then, a foam-cuttings two phase flow model was established and a numerical simulation was performed by the modified Simple method. The calculated results indicate that the cuttings concentration could be more accurately determined by steadily solving the multiphase flow equations. The larger the cuttings size, the higher the cuttings concentration, while the cuttings with more irregular shapes will lead to lower cuttings accumulation. With the increasing of injection, the annular cuttings concentration increases in shallow well sections, while decreases in deep ones. Taking into account the effect of acceleration forces and the slip velocity between foam and cuttings, this proposed model is used to obtain the predicted bottomhole pressure closer to the experimental data and the annular cuttings concentration is more accurate than ever before.