| Steam Assisted Gravity Drainage(SAGD)is one of the most significant technologies for heavy oil recovery.A steam chamber is formed by injecting hot steam through the injection well which is above the production well horizontally,and the heated heavy oil flows downward to the production well by gravity.Based on previous studies,several calculation models have been proposed in this paper.Considering the heat transfer between production well and injection well,a wellbore heat transfer model for SAGD production well is established.Considering the influence of narrow-boiling fluid on flash calculation,an improved isenthalpic flash calculation model is established.Considering the phase transformation and the interaction between wellbore temperature and pressure,a wellbore temperature-pressure coupling calculation model is established on the basis of flash calculation model,heat transfer model and two-phase flow theory.The accuracy of the new model has been verified by analyzing the calculation result of an example well.Comparing calculation results of this model and PIPESIM,the advancement of this model has been analyzed.The influence of various parameters of production well and injection well on wellbore temperature and pressure are analyzed based on this model.In addition,the calculation model is applied to artificial lift design in this paper.It is found that the pump efficiency reduced due to the phase transformation of water and light components,which could be effectively improved by changing the pump depth.The wellbore temperature-pressure coupling calculation model established in this paper can be used in swabbing parameters optimization,artificial lift design and wellbore behavior analysis,which is essential to improve oil production by SAGD. |
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