Flow Field Analysis And Performance Evaluation Of Oil-gas-water Separator In System Of Same Well Injection And Production

With the continuous development of oilfields,the water content of oilfield produced fluids has gradually increased,and the volume of ground produced fluids has become larger and larger.The original equipment cannot guarantee the continuous operation of existing production.In order to solve this problem and reduce the expansion and investment of surface equipment,the same-well injection-production technology is proposed and applied in practice.The same-well injection and production technology realizes oil-water separation in the wellbore of the oil well.Generally speaking,about 80% of the liquid volume(qualified water)separated in the wellbore is directly injected into the corresponding formation,and about 20% of the separated liquid volume(rich fluid)is lifted to the ground.However,the liquid before entering the separator in the wellbore contains not only oil,water,but also a certain amount of gas sometimes.When the gas content is large,it will seriously affect the separation efficiency of the cyclone separator in the wellbore.In this paper,related research is carried out on the downhole oil-gas-water three-phase cyclone separator designed based on the principle of cyclone separation,which provides a basic guarantee for the efficient operation of the cyclone separator in the wellbore of high gas content oil wells.In this paper,based on the application of Compution Fluid Dynamic(CFD),the initial structure of the designed downhole oil-gas-water three-phase cyclone separator is carried out to conduct fluid domain modeling,grid differentiation and corresponding independence test.Orthogonal experiments were used to combine different throughputs,gas-liquid ratios,and oil contents,and numerical simulations were carried out;the operating parameters were optimized according to the gas-phase separation efficiency,and the gas-phase separation efficiency under different operating parameters was clarified.The single factor analysis method is used to simulate the fluid domain of the downhole oil-gas-water three-phase cyclone separator.The internal velocity field,concentration field,pressure loss,and the separation efficiency of the oil-gas-water three-phase cyclone under different conditions were also studied.The research results show that the parameters of the treatment capacity of 5m3/h,the gas-liquid ratio of20%,and the oil content of less than 5% are the optimal conditions for the downholeoil-gas-water three-phase cyclone.In order to verify the accuracy and reliability of the numerical simulation,the laboratory experiment of the prototype was carried out,and the separation performance was studied under the conditions of different gas-liquid ratio,oil content and processing capacity.At the same time,the data of gas phase separation efficiency,oil phase separation efficiency and pressure loss were compared with the numerical simulation results.The results show that the theoretical data is consistent with the experimental data and the deviation is small,which shows that the oil-gas-water three-phase cyclone used in the downhole can meet the separation requirements of the medium,and also shows the reliability of the numerical simulation results in this paper.