二氧化碳扩散系数的实验研究和模型计算

Experimental studies and modeling calculation of carbon dioxide diffusion coefficients

采用动态界面张力法研究二氧化碳(CO_2)在中原油田胡12块轻质原油的传质速率问题。实验中原油-CO_2体系的动态和平衡界面张力通过悬滴法测定。理论上,建立一个数学模型得到任何时间下的动态界面张力。目标函数用来表示不同时间理论计算和实验测得的动态界面张力的均方根相对误差。CO_2扩散系数和传质Biot数作为适当的参数,当目标函数最小化时,就能确定扩散系数和传质Biot数。由数值模拟得出:300. 15 K,0. 5～4. 1 MPa下,CO_2在原油的扩散系数、传质Biot数和界面传质系数分别为(0. 45～4. 61)×10^(-9)m^2/s,2. 5～7. 1和(0. 85～8. 33)×10^(-5)m/s,模型计算与实验测得动态界面张力的均方根相对误差低于1. 81%。

The dynamic interfacial tension method has been applied to study the mass transfer rate of CO 2 in Hu 12 block light crude oil of Zhongyuan Oilfield.The dynamic and equilibrium interfacial tensions are measured by pendant drop method.Theoretically,a mathematical model is formulated to obtain the dynamic interfacial tension at any time.Subsequently,an objective function is constructed to express the root mean square relative error between the numerically calculated and the experimentally measured dynamic interfacial tensions at different times.The CO 2 diffusion coefficient and mass-transfer Biot number are used as parameters and then determined once the minimum objective function is achieved.From numerical simulation,the diffusion coefficient,the mass-transfer Biot number,and the interface mass-transfer coefficient of CO 2 in crude oil at 300.15 K and 0.5~4.1 MPa are(0.45~4.61)×10-9 m 2/s,2.5~7.1,and(0.85~8.33)×10-5 m/s,respectively.The root mean square relative errors of dynamic interfacial tensions between model calculation and experimental determination are less than 1.81%.