基于试验和CFD模拟的稠油热采井口四通管冲蚀规律分析

目的 分析稠油热采中含砂流体对四通管冲蚀磨损问题,明确失效机理及特征.方法 采用金相分析仪对失效四通管损伤处材料ZG(J)35CrMo进行金相组织分析,并采用扫描电镜(SEM)对四通管进行冲蚀形貌微观检测,同时借助多相流冲蚀试验机对四通管材料ZG(J)35CrMo进行冲蚀试验,构建冲蚀预测模型,并通过单因素冲蚀试验对冲蚀预测模型进行验证.最后建立CFD-DPM-EPM(耦合计算流体动力学-离散粒子-冲蚀)数值模型,研究不同流体速度、颗粒粒径和质量流量对四通管冲蚀规律的影响.结果 金相组织分析结果显示,失效四通管材料基体组织成分为索氏体、铁素体和贝氏体,表面发生轻微脱碳现象.扫描电镜分析结果显示,失效四通管内壁有明显的砂粒冲蚀形貌,材料无明显的材质劣化及脆断现象.单因素冲蚀试验验证了回归分析法构建的冲蚀模型的准确性.随着流体速度由5 m/s增加至25 m/s,四通管最大冲蚀速率增加了16.947倍;颗粒粒径由0.05 mm增加至0.2 mm时,四通管最大冲蚀速率减少了50％,而颗粒粒径由0.2 mm增加至0.4 mm时,四通管最大冲蚀速率增加了1.382倍;质量流量从0.15 kg/(m2·s)增加至2.4 kg/(m2·s)时,最大冲蚀速率增加了16.584倍.结论 四通管失效主要由于颗粒冲蚀管道内壁,管道减薄到一定程度后,无法承受内部压力所致.四通管出口段肩部为冲蚀高危区.随流体速度的增加,四通管最大冲蚀速率呈指数关系增加;随着颗粒粒径的增加,最大冲蚀速率呈先减小后增大的趋势;当质量流量增加时,最大冲蚀速率呈线性关系增加.

Analysis of Erosion Law of Four-way Pipe in Heavy Oil Thermal Production Wellhead Based on Experiment and CFD Simulation

The work aims to study the problem of erosion and wear on four-way pipe by fluid carrying sand in heavy oil thermal production, so as to define the failure mechanism and characteristics. The metallographic analysis of ZG(J)35CrMo of the damaged four-way pipe was analyzed by metallographic analyzer, and the micro erosion morphology of the four-way pipe was analyzed by scanning electron microscope (SEM). At the same time, the erosion experiment of four-way pipe material ZG(J)35CrMo was carried out by the multiphase flow erosion tester, and the erosion prediction model was established and verified by the single factor erosion experiment. Finally, CFD-DPM-EPM (coupled computational fluid dynamics-discrete particle-erosion) numerical model was established to study the influence of different fluid velocities, particle size and mass flow rate on the erosion law of four-way pipe. The metallographic analysis result shows that the matrix structures of the material were sorbite, ferrite and bainite, and there is slight decarburization on the surface. SEM results show that the inner wall of the failed four-way pipe has obvious sand erosion morphology, and the material has no obvious deterioration and brittle fracture phenomenon. The erosion prediction model is verified by single factor erosion experiment, which proves the accuracy of erosion prediction model constructed by regression analysis method. With the increase of fluid velocity from 5 m/s to 25 m/s, the maximum erosion rate of the four-way tube increased by 16.947 times. When the particle size increased from 0.05 mm to 0.2 mm, the maximum erosion rate of the four-way tube decreased by 2.183 times. However, when the particle size increased from 0.2 mm to 0.4 mm, the maximum erosion rate of the four-way tube increased by 1.382 times. When the mass flow rate increased from 0.15 kg/(m2.s) to 2.4 kg/(m2.s), the maximum erosion rate increased by 16.584 times. The failure of the four-way pipe is mainly due to the erosion of the inner wall of the pipe by particles, and the four-way pipe can not bear the internal pressure after being thinned to a certain thickness. The shoulder of the exit section of the four-way pipe is a high-risk area of erosion, and the maximum erosion rate of the four-way pipe increases exponentially with the increase of the fluid velocity, and with the increase of particle size, the maximum erosion rate decreases first and then increases. When the mass flow rate increases, the maximum erosion rate increases linearly.