基于CPA状态方程计算水的热力学物性参数

发布时间：2018-10-04 19:17

【摘要】：虽然储层多孔介质中不可避免的含有大量的地层水,但在通常的相平衡计算过程中往往都忽略了水的存在;常用的状态方程虽然计算简便,但对某些热力学性质的估算仍存在着较大的偏差;已有的状态方程虽然已进行过修正,但其对含有极性物质(烃类、水、醇等)的体系适用性较差。为此,基于同时考虑分子间物理作用和缔合作用的CPA(Cubic-Plus-Association)状态方程,模拟计算了极性物质——水在饱和与非饱和状态下的热力学性质,对比分析了常用状态方程在计算极性物质热力学物性参数时的不足。计算结果表明:(1)常用的状态方程虽然能较好地计算水的饱和蒸汽压值,但在水的密度和焓值的计算时却呈现出不同的差异性,同时焓值的计算不受体积修正的影响;(2)CPA方程计算的水热力学物性参数与实验数据的平均绝对相对偏差在1%左右。结论认为:对含有极性物质的体系而言,CPA方程是首选的热力学状态方程。对水热力学物性参数的准确估算是对含水气藏流体所处状态的基础把握,对该类气藏的开发和生产具有重要的指导意义。
[Abstract]:Although the reservoir porous media inevitably contains a large amount of formation water, it is often ignored in the ordinary calculation of phase equilibrium, and the commonly used equation of state is easy to calculate. However, there is still a large deviation in the estimation of some thermodynamic properties. Although the existing equation of state has been modified, its applicability to systems containing polar substances (hydrocarbons, water, alcohols, etc.) is poor. Therefore, based on the CPA (Cubic-Plus-Association) equation of state which considers the intermolecular physical interaction and association interaction, the thermodynamic properties of the polar matter-water in saturated and unsaturated states are simulated and calculated. The deficiency of the commonly used equation of state in calculating the thermodynamic properties of polar matter is compared and analyzed. The results show that: (1) although the commonly used equation of state can well calculate the saturated vapor pressure of water, it shows different differences in the calculation of water density and enthalpy. At the same time, the calculation of enthalpy is not affected by volume correction. (2) the average absolute relative deviation between the thermodynamic properties of water calculated by CPA equation and the experimental data is about 1%. It is concluded that the CPA equation is the preferred thermodynamic equation of state for the system containing polar substances. The accurate estimation of the thermodynamic physical parameters of water is the basic understanding of the fluid state of the water-bearing gas reservoir and has important guiding significance for the development and production of this kind of gas reservoir.
【作者单位】： "油气藏地质及开发工程"国家重点实验室·西南石油大学;中海石油(中国)有限公司天津分公司;
【基金】：国家自然科学基金项目“考虑毛细管压力和吸附影响的CO_2——原油非平衡扩散理论及分子动力学研究”(编号:51374179) 国家留学基金西部地区人才培养特别项目(编号:201508515157)
【分类号】：TE31

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