| Along with the application of CO2 oil displacement technology in the exploitation of oil field,freeze blockage often happens in gathering pipeline network,which result in the failure of the whole system and influnce the effect of CO 2 oil displacement exploitation.In this paper,research mainly focus on the flow assurance of ground transmission pipeline system of CO2 oil displacement,the mechanism and corresponding measures of freeze blockage of CO2 oil displacement pipelines.According to the characteristics of large oil-gas proportion and high percentage of CO2,the calculation method of flow parameters of CO2 oil displacement produced fluid is designed.Based on field data and theoretical analysis,Brinkman oil-water viscosity calculation model and Beggs-Brill pressure drop calculation model are more appropriate for the research.What's more,thermodynamic calculation model is built in consider of the influence of percentage of water added in oil and different gas compositions.The research aimed to find out the mechanism of freeze blockage of CO2 oil displacement gathering pipelines is carried out.The result shows that low temperature sticky wall effect,throttling effect and CO2 hydrates dissociation or endothermic gasification of liquid CO2 are the main three reasons to cause freeze blockage.Also,sensitive analysis method is used for the three kinds of main mechanism.Result shows that low temperature sticky wall effect is the main freeze blockage reason for high percentage of water recovery fluid.Otherwise,CO 2 phase change endothermic influences more in freeze blockage for low percentage of water recovery fluid.On the basis of the research of hydraulic and thermal calculation models and freeze blockage mechanism,a flow assurance software for CO2 oil displacement gathering pipelines is programmed.Also,three measures to prevent and solve CO 2 oil displacement gathering pipeline is given.And applicability of different method is stated. |
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