CO2在原油中的扩散规律及变扩散系数计算方法

Diffusion law and measurement of variable diffusion coefficient of CO_2 in oil

通过室内实验与理论计算相结合建立CO_2在体相及多孔介质中变扩散系数的计算模型,得到不同黏度原油在多孔介质中的变扩散系数,并结合文献中的常扩散系数计算模型,利用MATLAB进行数据拟合与编程,对比分析两种计算方法下的平均扩散系数以及CO_2在溶液中的传质扩散行为。结果表明:原油黏度越大,扩散系数越小,扩散平衡时间越长;采用变扩散系数可以更好地解释扩散过程中的非稳定阶段与稳定阶段,其扩散行为更符合实际条件下的扩散规律。

A mathematical model of variable diffusion coefficient of CO2 which can be used in bulk and porous media was established through the experiment and theoretical calculation. The variable diffusion coefficients of CO2 in oils with different viscosity were calculated with this developed model. In order to validate this model, a traditional model of constant diffusion coefficient was used to calculate the average diffusion coefficient. The calculations with MATLAB software for the two models to analyze the diffusion coefficients and diffusion behaviors were also compared. The results show that the greater the viscosity of crude oil, the smaller the diffusion coefficient and the longer the diffusion equilibrium time. Diffusion behaviors of real condition, which contains unstable and stable stages, can be explained by the variable diffusion coefficient model with better results.