泡沫钻水平井岩屑颗粒的运移规律研究

Migration Law Study on Cuttings Particles for Foam Drilling in Horizontal Wells

水平井岩屑大量堆积会引起摩阻和扭矩增加,还可能出现许多复杂问题,严重时会出现卡钻事故,甚至影响后续作业。为了研究大斜度及水平井中岩屑的输送规律,文章基于泡沫流体的特殊流变模型,建立了垂直/近垂直段、过渡段和大斜度/水平段岩屑输送的数学模型,并对岩屑床厚度随井斜角的分布特征以及不同泡沫流动参数对环空岩屑床厚度的影响规律进行分析。结果表明,井斜角、环空速度、泡沫质量、岩屑粒径和偏心度是影响环空岩屑传输的关键因素。环空中岩屑床的厚度随着井斜角的减小而减小;随泡沫流速、质量的增大而减小;随钻柱偏心度增大而增大。因此在现场作业中,在大斜度井段应降低钻柱偏心度,保证钻柱居中度,同时旋转钻柱、提高泡沫流速或增加泡沫质量来减小岩屑床的厚度,以便更好地改善井眼的清岩效果。

The massive accumulation of drilling cuttings in horizontal wells can cause drag and torque increasing and many other complex problems, even sticking and affect subsequent operations. In order to study the transportation law of cuttings in highly deviated and horizontal wells, this paper based on the special rheological model of foam fluid, the mathematical models of cuttings transportation for stable foam drilling in vertical/near vertical sections, the transitional section, and highly inclined/horizontal sections are established. The distribution characteristics of the cutting bed thickness with well inclination and the effect of various flow parameters on the cutting bed thickness in the annular are analyzed. The results show that inclination, annulus velocity, foam flow rate, cuttings particle size and eccentricity are the key factors affecting cuttings transportation. The thickness of the cuttings bed decreases with the decrease of the inclination, decreases with the increase of foam flow rate and mass, increases with the increase of drill string eccentricity. Therefore, in field operations, the eccentricity of the drill string should be reduced in the highly deviated section to ensure the centering of the drill string, while rotating drill string, increasing the foam flow rate or increasing the foam quality to reduce the thickness of the cuttings bed, so as to better improve the cleaning effect of the wellbore.