石油学报 ›› 2015, Vol. 36 ›› Issue (5): 593-599.DOI: 10.7623/syxb201505008

• 油田开发 • 上一篇    下一篇

Gibbs自由能最小化法计算二氧化碳-烃-水系统相平衡

邸元1, 张园1, Wu Yu-Shu2   

  1. 1. 北京大学工学院 北京 100871;
    2. Petroleum Engineering Department, Colorado School of Mines Golden Colorado 80401
  • 收稿日期:2014-11-06 修回日期:2015-02-17 出版日期:2015-05-25 发布日期:2015-06-10
  • 通讯作者: 邸元,男,1968年2月生,1985年获西安交通大学学士学位,1995年获同济大学博士学位,现为北京大学工学院副教授,主要从事多孔介质多相流数值模拟、岩土力学等方面的研究工作。Email:diyuan@mech.pku.edu.cn
  • 作者简介:邸元,男,1968年2月生,1985年获西安交通大学学士学位,1995年获同济大学博士学位,现为北京大学工学院副教授,主要从事多孔介质多相流数值模拟、岩土力学等方面的研究工作。Email:diyuan@mech.pku.edu.cn
  • 基金资助:

    国家重大科技专项(2011ZX05014-005)和国家重点基础研究发展计划(973)项目(2011CB201004)资助。

Phase equilibrium calculation of CO2-hydrocarbons-water system based on Gibbs free energy minimization

Di Yuan1, Zhang Yuan1, Wu Yu-Shu2   

  1. 1. College of Engineering, Peking University, Beijing 100871, China;
    2. Petroleum Engineering Department, Colorado School of Mines, Golden Colorado 80401, USA
  • Received:2014-11-06 Revised:2015-02-17 Online:2015-05-25 Published:2015-06-10

摘要:

油-气-水三相的相平衡计算是二氧化碳驱物性参数分析及数值模拟研究的核心问题之一。Gibbs自由能最小化法基于相平衡的热力学理论,适应性广、计算稳定,比较适合二氧化碳-烃-水系统的相平衡计算。通过引入相稳定性变量,采用拉格朗日乘数法计算多相多组分系统Gibbs自由能的最小化问题,由Newton-Raphson迭代法求解相应的控制方程。迭代计算时,二氧化碳和烃类组分气-油平衡常数的初值采用Wilson公式进行计算。气相和油相的状态方程采用SRK方程。分别计算了凝析气、酸气和二氧化碳-烃混合物3个算例的相平衡问题,计算值同实验实测值符合良好,验证了算法的准确性。分别对二氧化碳-烃系统和二氧化碳-烃-水系统算例的相平衡进行了计算,研究了一定温度和压力条件下,系统内二氧化碳和水的含量对烃类组分平衡常数的影响。

关键词: 相平衡, Gibbs自由能最小化, 平衡常数, 多组分混合物, 二氧化碳

Abstract:

Phase equilibrium calculation of oil-gas-water system is one of the most essential problems for properties analysis and numerical simulation of carbon dioxide flooding. Based on thermodynamics of phase equilibrium, Gibbs free energy minimization is an adaptable and stable method, and is very suitable for three-phase equilibrium calculations of carbon dioxide-hydrocarbons-water system. A phase stability variable was defined, and the Lagrange multiplier method was used for Gibbs free energy minimization problem of multiphase and multicomponent systems. The corresponding governing equations were solved by Newton-Raphson method. The initial gas-oil equilibrium constants of carbon dioxide and hydrocarbon components were obtained by Wilson equation. The SRK equation of state was adopted for gas and oil phase. Several multicomponent examples were calculated, including condensate gas, sour gas and mixtures of carbon dioxide-hydrocarbons. The simulated results agree reasonably well with the experimental data reported in the literature. The examples of carbon dioxide-hydrocarbon system and carbon dioxide-hydrocarbons-water system were also calculated. The effects of contents of carbon dioxide and water on the equilibrium constants of hydrocarbons under certain conditions of temperature and pressure were presented.

Key words: phase equilibrium, Gibbs free energy minimization, equilibrium constant, multi-component mixture, carbon dioxide

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