段塞流下CO2驱采出流体分离器设计与模拟研究

Design and Simulation of Fluid Separator for CO2 Flooding under Slug Flow

在CO2驱采油工艺中,通常将超压套管气间歇性排入采油管线,导致采出流体气液比增高甚至形成段塞流。为解决分离器内高速段塞气体二次携带液体的问题,根据油气分离理论和相关规范,设计了双筒分离器,建立了不同预置液位下单、双筒分离器模型,通过数值模拟得到分离器内部液相体积分数、气出口含液体积分数、液体出口含气体积分数以及压力损失等,对比分析了单、双筒分离器分离效果。分析结果表明:双筒分离器的内部流场更加稳定,避免了发泡原油冒罐事故,分离器内液体也不会从气出口冲出;双筒分离器气出口含液体积分数相较于单筒分离器从67.3%下降到4.1%;液体出口含气体积分数从26.4%下降到8.2%;两种分离器压力损失相差较小,新设计的双筒分离器分离效果优于现有的单筒分离器。所得结论可为CO2驱采出流体分离器的设计、选型和运行提供参考。

During the oil production with the method of CO2 injection,overpressure casing gas is usually discharged into the production pipeline intermittently,which leads to the increase of gas-liquid ratio of produced fluid and even the formation of slug flow. In order to solve the problem of secondary liquid carried by high-speed slug gas in the separator,according to the oil-gas separation theory and relevant specifications,a double cylinder separator was designed. And the single-cylinder and double-cylinder separator models with different preset liquid levels were established. Through numerical simulation,the volume fraction of liquid phase in the separator,the liquid volume fraction at the gas outlet,the gas volume fraction at the liquid outlet and the pressure loss were obtained. The separation effect of single and double cylinder separators is compared and analyzed. The analysis results show that: the internal flow field of the double cylinder separator is more stable,avoiding the tank boil-overs of foaming crude oil,and the liquid in the separator will not rush out from the gas outlet;the liquid volume fraction at the gas outlet of the double cylinder separator decreases from 67. 3% to 4. 1%;the gas integral number at the liquid outlet decreases from26. 4% to 8. 2%;the pressure loss difference between the two separators is small. The separation effect of the new designed double cylinder separator is better than that of the existing single cylinder separator. The conclusion can provide reference for the design,selection and operation of fluid separator for oil production with CO2 injection method.