有杆泵井下油水分离系统设计与分析

Design and Analysis of Downhole Oil-Water Separation System for Rod Pump

随着油田开采进入高含水阶段,大量采出水的举升和处理使得采油经济效益越来越低。鉴于此,结合我国油田实际情况,提出一种新型有杆泵井下油水分离系统。该系统由注采式一体泵与两级串联旋流器连接,可实现同井采注。基于正交试验设计,以底流口含油质量浓度CU为目标,通过Fluent软件采用RSM雷诺应力模型优化旋流器主要结构参数。同时对两级串联油水分离旋流器内部流场分布情况进行分析,深入研究不同入口速度下两级串联旋流器的分离效率。研究结果表明:结构优化后的单级旋流器CU降低8.7%;两级串联旋流器内部流场具有较强的油水分离能力;不同入口速度下,两级串联旋流器油相体积分数最高可达100%,CU均低于200 mg/L,满足回注标准,其中在曲柄转角φ2=60°和φ3=90°处CU最小,为118 mg/L。该方案能在井下有效进行油水分离,使得分离水相达到回注标准,节省采油成本。

As oilfield development enters the high water cut stage,the lifting and treatment of a large amount of produced water makes the economic benefits of oil production lower and lower.Combining the actual situation of domestic oilfields,a new type of rod pump downhole oil-water separation system is proposed.The system is connected by an injection-production integrated pump and a two-stage series cyclone to realize production and injection in the same well.Based on the orthogonal experimental design,the main structural parameters of the cyclone are optimized using the RSM Reynolds stress model by the Fluent software targeting the minimum mass concentration of oil in the underflow port.The internal flow field distribution of the two-stage series oil-water separation cyclone is also analyzed to deeply study the separation efficiency of the two-stage series cyclone under different inlet velocity.The research results show that the CUof the single-stage cyclone with optimized structure is reduced by 8.7%.The internal flow field of the two-stage series cyclone has good oil-water separation ability.At different inlet velocities,the oil phase volume fraction of the two-stage series cyclone can reach up to 100%,and the CUis lower than 200 mg/L,which meets the re-injection standard.The CUis the smallest at the crank angle of 60°and 90°,which is118 mg/L.This scheme can effectively carry out downhole oil-water separation,so that the separated water phase can reach the reinjection standard,and the oil production cost can be saved.