高产天然气井放喷管汇弯管冲蚀磨损特性研究

目的 研究高产天然气井气固两相流对放喷管汇的冲蚀机理及规律.方法 利用CFD软件对放喷管汇冲蚀进行研究,使用雷诺平均Navier-Stokes(RANS)方程求其气相的运动状态,并用离散相模型(DPM)计算出颗粒运动轨迹.然后使用Oka冲蚀磨损模型开展弯管角度、弯管位置、放喷量等5种因素与壁面冲蚀规律研究,最后使用最大冲蚀速率、壁面质量损失以及管汇刺漏时间等3种指标评价管汇的冲蚀特性.结果 在控制单因素变量的前提下,随着含砂率从1％增长到5％时,弯管最大冲蚀速率增加了约4倍;随着放喷量从3.0×105 m3/d增加到5.1×106 m3/d时,最大值出现在1.0×106 m3/d附近,弯管最大冲蚀速率相比3.0×105 m3/d增加了3.7倍;当弯管角度从90°增加到165°时,最大冲蚀速率下降了85％,但120°弯管最大冲蚀速率最大;随着弯管距出口距离从5 m增加到30 m时,最大冲蚀速率下降了86％;当颗粒形状系数从0.67增加到1时,最大冲蚀速率增大了5倍.结论 含砂率与最大冲蚀速率相关度最大,弯管位置与最大冲蚀速率的相关度最小.最大冲蚀速率随含砂率、颗粒形状系数的增加而增大,随弯管角度和距出口直管段长度的增加而减小,但120°弯管冲蚀最严重.随放喷量的增加,弯管最大冲蚀速率呈现出先增大、后减小、最后趋于平稳的规律.

Study on Erosion Characteristics of Elbow Erosion of Manifold for Relief Pressure of High-yield Natural Gas Well

The work aims to study the erosion mechanism and law of gas-solid two-phase flow on the manifold for relief pressure of high-yield natural gas well. During the study of the erosion of manifold for relief pressure by CFD software, Reynolds average Navier-Stokes (RANS) equation was used to obtain the gas phase motion state. The particles tracks were captured by the discrete phase model (DPM). Then, the Oka erosion model was used to study the relationship between the five factors such as the angle of the elbow, the position of the elbow, and the discharge volume and the erosion law of the pipe wall. Finally, the maximum erosion rate, wall quality loss and pipeline puncture time were used to evaluate the erosion of manifold for relief pressure. Under the premise of controlling the single factor variable, as the percentage sand increased from 1% to 5%, the maximum erosion rate of the elbow increased by about 4 times. When the discharge volume increased from 3.0×105 m3/d to 5.1×106 m3/d, the maximum erosion rate appeared near 1.0×106 m3/d approximately, which increased by 3.7 times compared with 3.0×105 m3/d. When the bend angle increased from 90° to 165°, the maximum erosion rate declined by 85%. The maximum erosion rate of elbow at 120° is the largest. As the distance from the elbow to the outlet increased from 5 m to 30 m, the maximum erosion rate decreased by 86%. When the particle shape factor increased from 0.67 to 1, the maximum erosion rate increased by 5 times. The correlation between sand content and maximum erosion rate is the greatest, while the correlation between the position of the elbow and the maximum erosion rate is the smallest. The maximum erosion rate increases with the increase of percentage sand and particle shape coefficient, and decreases with the increase of elbow angle and straight pipe length from outlet. However, the maximum erosion rate of the elbow pipe at 120° is the largest; with the increase of the discharge volume, the maximum erosion rate of the elbow increases firstly, next decreases, and ultimately stabilizes.