The Study On CO₂+ Crude Oil+water Phase Equilibrium

The study found that the use of oil fields to achieve CO₂ storage can not only reduce its impact on the climate to a certain extent,but also use CO₂ to improve the recovery of crude oil and achieve the purpose of CO₂ storage.However,a series of basic researches are needed in this process,one of which is the solubility of CO₂ in crude oil,it has a great influence on the entire oil displacement process and the storage effect.In this paper,crude oil and water are used as research objects.The solubility of CO₂in pure water,crude oil and different proportions of oil-water mixture is measured.The experimental temperature ranges from 313.15K to 423.15K and the pressure range from5MPa to 25MPa.The dissolution laws of CO₂ in oil phase,water phase and oil-water mixture are explored.It is found that its solubility in water increases with the increase of pressure and decreases with the increase of temperature,but when the temperature is higher than373.15K,the solubility increases with higher pressure.Comparing the experimental values with the literature values,the average relative error is 2.0%.The solubility in the oil and oil-water mixture increases with the increase of the pressure and decreases with the increase of the temperature.It has been found that the solubility of CO₂ in oil-water mixture is closely related to its liquid phase composition and experimental pressure under constant temperature conditions,and is not affected by other conditions.Therefore,the solubility data in oil phase and water phase can be used to estimate the solubility of CO₂in the oil-water mixture under the same temperature and pressure.A solubility model suitable for high temperature and high pressure systems is established.The PR equation is used to calculate the solubility of CO₂ in water with an average error of 2.32%,Compared with the calculated values of the Duan model under the same conditions,the error is the smaller.The critical parameters of crude oil are calculated by empirical correlation.The solubility model of CO₂ in crude oil is established by the PR equation of state.The average relative error is 3.60%.Compared with the SRK model under the same conditions,the prediction effect is closer to the experimental value.The relationship between the solubility of oil-water mixture and the solubility of pure oil phase and water phase is clarified.The solubility of CO₂ in oil-water mixture can be estimated by the establishment of oil phase and water phase solubility prediction model,which lays a foundation for further research.