抽油泵-气锚组合防气性能仿真分析

Simulation and analysis of anti-gas performance of pump-air anchor combination

油田在高含气油井开发过程中,通常采用气锚对井下气液混合介质进行进泵前的气液分离。在气液两相流理论基础上,研究重力型气锚在井下的分离效率。将套管、气锚和抽油泵作为整体研究对象,分析在抽油泵整个工作循环气锚的分离效率。建立套管、重力型气锚和抽油泵的一体化三维流体域模型,气液分析模型选择流体体积法(VOF)。为了更接近实际工况,在保持套管动液面不变的情况下,计算出套管入口流速作为仿真模型的入口边界条件。用动网格技术对抽油泵柱塞设置曲柄连杆运动作为仿真模型的计算边界条件。仿真分析在高气液比井中,入口液体流速越大,气锚分离效率越低。气锚结构参数对气液分离效率影响较大,相同尺寸的套管,选择尺寸越小的外管,气锚的分离效率就越好,中心管的尺寸大小对气锚分离效率影响很小。

In the process of high gas content oil well development,gas anchor is usually used to separate gas and liquid mixture before pumping.Based on the theory of gas-liquid two-phase flow,the gas separation efficiency of gravity gas anchor is studied in this paper.Taking casing,gas anchor and pump as the whole research object,the separation efficiency of gas anchor in the whole working cycle of the pump is studied.The integrated three-dimensional fluid domain model of casing,gravity gas anchor and pump was established,and volume of fluid(VOF)was selected as the gas-liquid analysis model.In order to get closer to the actual working conditions,the casing inlet flow velocity was calculated as the inlet boundary condition of the simulation model under the condition of keeping the casing fluid level unchanged.The motion of crank and connecting rod is used as the boundary condition of the simulation model.Simulation analysis shows that in high gas-liquid ratio Wells,the higher the inlet fluid velocity is,the lower the gas-anchor separation efficiency is.The gas anchor structure parameters also have an important effect on the gas-liquid separation efficiency:the smaller the outer pipe of the gas anchor is,the better the separation performance is.The size of anchor center tube has little effect on separation performance.