井下两级旋流分离技术流场模拟研究

随着油田开采程度的持续深入,降低生产成本和提高采出效率正逐渐成为各油田提高竞争力的重要手段。井下两级旋流分离技术可进一步提高分离效率,降低回注水的含油量,提升回注水品质,大幅度降低地面采出液及采出液含水率,是油田降低开采成本的重要举措及技术支持。通过井下两级旋流分离技术流场模拟研究,重点分析新型螺旋流道旋流器(一级旋流器)内部的流场特点,研究其速度矢量及速度分量的变化规律,压力损失特点和油相分布规律。新型结构的螺旋流道使流经其内部的流体从单一的轴向运动转变为旋转运动,流体运动空间的改变使其切向速度增加明显,有利于进行离心分离。流体在运动过程中的压力损失转变为流体的速度增量,与流体经过螺旋流道后速度矢量的变化相对应,但因循环流的存在,扰乱了溢流管下部油核及相邻位置流体的正常运动,使油核发散、流场紊乱,令新型结构的旋流器效率有所降低。经过流场分析,进一步认识井下两级旋流分离器的流场分布规律,有利于旋流器的结构改进及现场应用。

Research on Flow Field Simulation of Downhole Two-stage Cyclone Separation Technology

With the continuous deepening of oilfield exploitation,reducing production cost and improving production efficiency are gradually becoming important indicators to improve the competitiveness of oilfields. Downhole two-stage cyclone separation technology can further promote separation efficiency,reduce the oil content of reinjection water,improve the quality of reinjection water,and significantly reduce the water content of surface produced fluid and produced fluid volume. It is an important measure and technical support to reduce the production cost of oilfield. Through the simulation study of downhole two-stage cyclone separation technology,the flow field characteristics of the new spiral channel hydrocyclone(first-stage hydrocyclone) are analyzed,and the variation rules of velocity vector and velocity component,pressure loss characteristics and oil phase distribution are studied. The new spiral channel makes the fluid change from single axial motion to rotational motion. The change of fluid motion space makes the tangential velocity increase obviously,which is beneficial to centrifugal separation. The pressure loss of fluid in motion is transformed into the velocity increment of fluid,which corresponds to the change of velocity vector after the fluid passes the spiral channel. However,due to the existence of circulating flow,the normal movement of the oil core at the lower part of the overflow pipe and the adjacent position of the fluid are disturbed,which makes the oil core diverge,the flow field disorder,and reduces the efficiency of the cyclone with new structure. Through flow field analysis,the flow field distribution law of downhole two-stage separation cyclone is further understood,which is conducive to the structural improvement and field application of cyclone.