CH_(4)、CO_(2)与稀有气体溶解度的估算模型及其地质应用

Solubility models of CH_(4),CO_(2) and noble gases and their geological applications

CH_(4)、CO_(2)、稀有气体的溶解度模型在地球科学领域应用广泛。它们的溶解度模型在研究流体包裹体的均一化压力、古气温变化、天然气运移与聚集规律、富氦天然气成藏、储层中气—水体积比等方面发挥着重要作用。主要综述了纯水与NaCl水溶液中CH_(4)、CO_(2)、稀有气体溶解度研究的新进展。重点介绍了精度高且适用性广的模型的建立过程及其适用范围,并给出了部分模型的计算结果。包括:(1)0~250℃、0.1~200 MPa、0~6.0 mol/kg NaCl溶液中CH_(4)的溶解度模型;(2)0~450℃、0.1~150 MPa、0~4.5 mol/kg NaCl溶液中CO_(2)的溶解度模型;(3)0~80℃范围内大气稀有气体溶解度与亨利常数的计算模型;(4)纯水中稀有气体亨利常数计算模型;(5)0.1 MPa、0~65℃、0~5.8 mol/kg NaCl溶液中稀有气体的溶解度模型。CH_(4)与CO_(2)的溶解度模型复杂,但精度高,适用范围广。稀有气体溶解度模型的精度相对较低,适用范围相对较小,有待进一步提高与改进。CO_(2)—稀有气体—水体系中,低密度的CO_(2)对稀有气体溶解度的影响较小,而高密度的CO_(2)对稀有气体的溶解度有较大的影响。目前还无法判断CH_(4)—CO_(2)—稀有气体共存时对彼此溶解度的影响程度,其混合气的溶解度模型需要加强研究。

Solubility models of CH_(4),CO_(2) and noble gases are widely used in earth sciences.Their solubility models play important roles in studying of homogenization pressure of inclusions,temperature variations in the past,gas migration and accumulation laws,helium gas pool formation,and volumetric ratio of natural gas and groundwater.Here,solubility models of CH_(4),CO_(2) and noble gases in pure water and aqueous NaCl solution is reviewed.These models with high precision and wide applicability are emphatically introduced,including:(1)CH_(4) solubility model in 0-250℃,0.1-200 MPa and 0-6 mol/kg NaCl solution;(2)CO_(2) solubility model in 0-450℃,0.1-150 MPa and 0-4.5 mol/kg NaCl solution;(3)Models for calculating solubilities and Henry’s constants of atmospheric noble gases at 0-80℃;(4)Models for calculating Henry’s constants of noble gases in pure water;(5)Solubility models of noble gases in 0.1 MPa,0-65℃and 0-5.8 mol/kg NaCl solution.Some calculated values by solving model equations are presented.The solubility models of CH_(4) and CO_(2) are more complex but highly accurate,and their application range is wide.However,the solubility models of noble gases have relatively low accuracy and narrow applicability,and thus need to be corrected.In noble gas-CO_(2)-H_(2)O system,there was no difference between measured noble gas partitioning and that predicted in pure noble gas-water system at low CO_(2) density.However,at high CO_(2) density,partition coefficients express significant deviation from pure noble gas-water systems.Currently,it is difficult to accurately evaluate respective solubility of CH_(4),CO_(2) and noble gases in their mixture,the solubility model of CH_(4)-CO_(2)-noble gases needs to be further studied.