Simulation And Optimization Of Downhole Gas - Liquid Separator

Aimed at the problem of prevention gas in high gas liquid ratio well, at present the most effective measure is to install downhole gas-liquid separator. Ever since downhole gas-liquid separator is applied, studies on the structure and separation mechanism of the separator have never stopped. Most scholars studied the factors that influence the efficiency of separator mainly from the separator structure. Researches to definite the working condition of separator are relatively scarce. In the aspect of using CFD simulating separator, there is a certain lack of choosing outlet boundary conditions of separator. To solve problems above, this paper has carried out following works:(1) Based on the flow pattern of vertical gas-liquid tow-phase flow, comparing and analyzing the adaptation of the Mixture model, the Volume of Fluid model and the Eulerian model, Eulerian multiphase flow control model and PBM gas control model suiting for the simulation of separator are picked out.(2) The working behavior of downhole gas-liquid separator is mainly affected by pump swabbing process. In this paper, dynamic mesh is used to simulate pump swabbing process, hence creating a more realistic separator working environment. At the same time, combining the downhole behavior of separator, pressure inlet boundary condition and pump swabbing exports condition are defined.(3) On the basis of the gravity sedimentation gas-liquid separator structure and the mechanism analysis on it, the physical model of the separator is established. Through the simulation analysis, this paper studies how the separator inlet rate is affected by slot inlets and holes inlets, and also studies and optimizes the number of holes and the eccentric position of center pipe. The simulation result shows that the structure of holes inlets overmatches slot inlets, and when the eccentric amount of center pipe is bigger than half radius of separation tube, the separation effect is better.(4) Conditions and fluid physical properties also affect efficiency of separator. This article researches and analyses the performance of separator how to be affected by the sinking pressure, gas-oil ratio, swabbing speed and viscosity respectively. Taking4MPa as pump intake pressure and using long stroke and low stroke frequency are recommended.(5) Screw blade angle can effectively change the flow field distribution of the screw separator. This paper analyzes the differences between screw angle and ordinary angle, using velocity field, pressure field and the cloud, the recommended screw angle is15°.(6) Whether downhole screw separator can play a screw separation role mainly depends on the fluid velocity. This paper simulates the up and down stroke process, analyzes and researches the fluid field distribution of this process. The simulation result shows that screw separation role can be active only when the fluid velocity on the screw achieves0.42m/s.