CO2-CH4体系热力学性质（PVTx）研究进展

Research progress on the thermodynamic properties（PVTx） of a CO2-CH4 mixture system

开展CO2-CH4体系热力学性质研究,可以为注CO2强化非常规天然气开采中气藏内CO2-天然气混合流体的流动、扩散及运移研究提供必要的基础热物性数据,具有重要的科学意义和研究价值.本文综述了基于压缩因子测量方法和密度/体积测量方法的CO2-CH4体系热力学性质实验研究、不同类型热力学状态方程研究的国内外现状,总结了现有研究的不足及研究动向.研究分析得出主要研究趋势包括:实验测量深层、超深层气藏高温高压(超高压)条件下CO2-CH4体系的高精度密度数据;开展高CO2浓度(x>0.90)CO2-CH4体系在临界区温度压力条件下的密度测量实验研究,分析其相态和PVTx变化规律;建立或发展适用于以上温度、压力条件的状态方程,准确预测CO2-CH4体系热力学性质变化规律.本研究为今后CO2-地下流体混合体系的热力学性质研究提供了参考和借鉴.

In applications of enhanced unconventional natural gas extraction by CO2,the thermodynamic properties study of the CO2-CH4 mixture system is of great significance for the flow,diffusion,and migration of CO2-natural gas fluid in gas reservoirs.This work reviews the status of the pressure-volume-temperature-composition(PVTx)experimental research for a CO2-CH4 system based on compressibility factor and density/volume methods,and modeling research on various types of thermodynamic equations of state.We also summarize the shortcomings of the existing research and point out study trends for future research.It is proposed in this work that the experimental measurement of high-precision density data of a CO2-CH4 system be conducted under high-temperature and ultra-high-pressure conditions corresponding to deep and ultra-deep gas reservoirs.The experimental density data for a CO2-CH4 system with a high CO2 concentration(x>0.90)in the vicinity of the critical point are also urgently required.The equation of state applicable to the above temperature and pressure conditions should be established or developed to accurately predict the thermodynamic properties of the system.The thermodynamic properties study of CO2-CH4 corresponding to enhanced unconventional natural gas extraction by CO2 in this work will provide a reference and guidance for future study of the thermodynamic properties of CO2-underground fluid mixture systems.