钻杆旋转影响大斜度井段岩屑分布的数值模拟

Numerical simulation of dillpipe rotation influence on cuttings distribution in highly inclined sections

为了研究钻杆旋转对复杂结构井大斜度井段环空岩屑分布状态的影响规律和钻井液-岩屑两相流动压降的变化规律,应用三维建模软件建立了复杂结构井大斜度井段物理模型,应用CFD动网格运动模型模拟钻杆在环空的旋转效果,流动域内采用Realizable涡黏模型近似求解钻井液-岩屑两相纳维-斯托克斯方程。模拟结果显示,钻杆旋转作用使岩屑沿井眼周向呈非对称状分布,钻杆旋转能够提高钻井液对岩屑沿切向的拖曳程度,显著提高了井眼清洁效果。根据CFD数值模拟结果,应用最小二乘法,结合Buckingham-π定理,建立了岩屑床比面积模型和环空压降计算模型。

In order to study the distribution of cuttings in annulus and pressure drop of cuttings and drilling fluid two-phase flow in high angle section of complex structural wells, 3D model of highly inclined sections of complex structural well is established and CFD dynamic grid technique is used to simulate the rotary effect of drillpipe. Realizable viscous model is adopted to calculate Navier-Stokes equation of cuttings and drilling fluid two-phase flow. The simulation results show that drillpipe rotation makes the cuttings asymmetrically distribute along the wellbore circumference, and improves the drag effect of drilling fluid in the tangential speed, which significantly enhances hole cleaning efficiency. Based on the numerical simulation results of CFD and combined with Buckingham-＇n＂ theorem, least square method is applied to establish the empirical correlations for estimating the ratio of cuttings bed area and wellbore area and the annular pressure drop.