CO2(CH4)-H2O-NaCl(CaCl2)体系在近临界区的气-液相平衡和PVTX性质的精确计算及应用

Understanding the thermodynamic properties (e.g. PVTx properties, vapor-liquid equilibrium) of the CO2(CH4)-H2O-NaCl(CaCl2) system over a wide P-T range is important for the use of fluid inclusions and for modeling heat and mass transfer in various geological environments. Equation of state (EOS) is the most suitable tool for this purpose. However, there is no EOS (or other thermodynamic models) allowing the accurate calculation of vapor-liquid equilibrium and PVTx properties of H2O-CO2 and H2O-CH4 binary systems, the CO2-H2O-NaCl ternary system at P-T conditions near to the critical regions. There is also no EOS suitable for CO2-H2O-CaCl2 and CH4-H2O-CaCl2 sysytems at temperatures higher than 523 K. This project will try to develop a crossover EOS which can calculate vapor-liquid equilibrium and PVTx properties of H2O-CO2, H2O-CH4, CO2-H2O-NaCl, CO2-H2O-CaCl2, CH4-H2O-NaCl and CH4-H2O-CaCl2 systems both near to and far from the critical regions of these systems within the P-T range from 273 to 723 K, and from 0 to 3000 bar. The methods for building this EOS include: (1) incorporating the renormalization group theory with the SAFT-LJ EOS improved by the proposer for the CO2(CH4)-H2O-NaCl(CaCl2) system below 523 K, (2) taking account of the contribution of intermolecular interactions among water, CO2, CH4, ions, ion pairs to Helmholtz energy. This study will also develop computer programs which allow the calculation of the composition, density and other parameters of fluid inclusions based on the new EOS and apply them to the analysis of fluid inclusions from hydrothermal gold deposits.

精确计算CO2(CH4)-H2O-NaCl(CaCl2) 体系在0-450℃、0-3000巴的温度、压力范围内的热力学性质对于热液金矿流体包裹体分析等研究有着重要意义。但是现有的状态方程均不能准确计算H2O-CO2、H2O-CH4二元系、CO2-H2O-NaCl、CH4-H2O-NaCl及CO2-H2O-CaCl2等气-水-盐三元系在近临界区的气-液相平衡和PVTx性质。本项目计划将处理近临界区密度涨落的重整化群理论与申请人最近通过改进SAFT-LJ方程建立的中低温气-水-盐体系方程相结合，考虑NaCl和CaCl2的部分电离并准确描述水、气体分子、离子对、离子间主要的分子（或离子）间作用力对体系自由能的影响，建立在0-450℃、0-3000巴的P-T范围内的近临界区和远临界区都精确的跨接状态方程来满足需求。在此基础上开发能够计算热液金矿流体包裹体V-x参数的计算机程序。

精确计算CO2(CH4)-H2O-NaCl(CaCl2) 体系在0-450℃、0-3000巴的温度、压力范围内的热力学性质对于热液金矿流体包裹体分析等研究有着重要意义。但是现有的状态方程均不能准确计算H2O-CO2、H2O-CH4等二元系、CO2-H2O-NaCl、CH4-H2O-NaCl及CO2-H2O-CaCl2等气-水-盐三元系在近临界区的气-液相平衡和PVTx性质。.本项目将前一项目为中低温气-水-盐体系建立的SAFT-LJ方程扩展到高温区域，考虑NaCl和CaCl2的部分电离并准确描述水、气体分子、离子对、离子间主要的分子（或离子）间作用力对体系自由能的影响，结合重整化群理论校正近临界区的密度涨落，建立了在近临界区和远临界区都精确的跨接状态方程。这一跨接方程能够准确计算CO2-H2O-NaCl、CH4-H2O-NaCl、CO2-H2O-CaCl2和CH4-H2O-CaCl2等气-水-盐三元体系（及所含的子体系如纯CH4、纯H2O、H2O-CO2、H2O-NaCl等）在0-450℃、0-3000巴的温度、压力范围内的气-液相平衡、PVTx等热力学性质，计算精度基本能够满足流体包裹体分析等地质地球化学研究的需求。另外本项目还研究了H2O-H2和H2O-N2体系气－液相平衡的准确计算、中低温条件下混合气体在卤水中的溶解度及CO2-卤水体系密度的准确计算等问题。. 本项目通过合作方式开展了CO2-H2O-NaCl和CO2-H2O-CaCl2体系相平衡性质的实验研究工作。以本项目的理论研究成果为基础开发了能够准确计算CO2(CH4)-H2O-NaCl(CaCl2)型热液金矿流体包裹体物理化学参数的应用软件。现已在国际知名SCI刊物”Fluid Phase Equilibria”上发表论文1篇，在中文核心期刊“高校地质学报”上发表论文1篇，另有3篇稿件正在整理和投送。总的来说，本项目顺利完成了预定的研究任务，所取得的理论成果基本达到了预期的技术指标。