| The produced fluid of oil field usually contains natural gas,water and so on.With the further development of oilfield,the formation energy decreases,the reservoir degassing,and the number of Wells with high gas fraction will increase.As an artificial lifting method,electric submersible pump has a wide range of applications in oilfield exploitation.Electric Submersible Pumps(ESPs)is sensitive to free gas due to its working principle.When the well fluid containing a large amount of free gas enters the ESPs unit,the performance of the pump will decline.In serious cases,cavitation corrosion and gas lock will occur,which will cause the displacement interruption of the pump,greatly reduce the lifting efficiency,and seriously affect the normal production of wells.In order to solve the above problems,this paper proposes a conveying concept of separating first and mixing later.According to this concept,based on the multi-phase flow experimental platform of the institute of mechanics,Chinese academy of sciences,the experimental prototype was designed and fabricated and the experimental research was carried out.The flow characteristics of gas-liquid two-phase mixed conveying were analyzed,including its flow field phase distribution,pressure and split ratio.In addition,by comparing the experimental results,the reliability of the numerical model analysis is verified,and the full-scale engineering numerical simulation is carried out.The study verified the feasibility of the concept of separating first and mixing later,and provide theoretical guidance for practical industrial applications.The specific research contents of the thesis are as follows:First,the experimental prototype is designed and the experimental research is carried out.By changing the inlet mixing flow rate,gas fraction and split ratio,the flow characteristics of gas-liquid separation and mixed conveying in the structure of the paper under different inlet working conditions are analyzed.The experimental results show that the separation and mixed conveying of gas-liquid two-phase can be achieved with good results under different inlet conditions.It verifies the rationality of the conveying concept of separating first and mixing later proposed in this paper.Secondly,the thesis establishes a numerical analysis model based on experiments,carries out numerical simulation analysis,Comparing the simulation results with the experimental results,the reliability of the model is verified,and the rationality of the Euler multiphase flow model and the RNG k-? double equation turbulence model used in the simulation is proved.Finally,based on the selected numerical model,the full-scale engineering model is simulated in this paper.The gas-liquid two-phase flow characteristics of the downhole gas-liquid separation and mixing structure are analyzed.The research results show that in the process of mixed conveying of gas-liquid two phases,the separation and mixing effect of gas and liquid is ideal for the actual engineering conditions.The concept of separation and post-mixing proposed in this paper can ideally realize the safe and stable operation of ESPs in high gas fraction wells.The research results provide a feasible method for improving the lifting efficiency of electric submersible pumps in high gas wells and increasing well production. |
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