Experimental Study On Interfacial Tension Of Carbon Dioxide-brine System Under Sub-seabed Storage

It is well known that the increasing amount of carbon dioxide emissions and the huge potential of carbon dioxide’s seabed storage technology.In order to analyzethe reliability ofsub-seabed sequestrationtheoryof carbon dioxide,this paper simulates the ocean conditions by means of experimental methods,and makes an accurate measurement of the important parameters of interfacial tension.In this paper,four groups of temperature(temperature range 285-300K),thirteen sets of pressure(pressure range 3.0-9.0MPa),five salinity(salinity range 0-1.8mol/L)were selected,under the conditions of each experiment was repeated five times;a total of 260 cases,1300 groups of experiments.In this paper,analysis-pendant drop method and quasistatic measuring procedure are adopted.The two-phase density data model selects the empirical model provided by the National Institute of Standards and Technology and theComputational Geochemistry Research Group.In this paper,the self-designed design of the pre-saturated brine container.This apparatus can simultaneously separate the saturated aqueous solution of carbon dioxide and the carbon dioxide saturated with the brine solution,also realize that the carbon dioxide and the brine are preliminarily saturated.The experimental results show that the increase of temperature will increase the density difference of saturated salt solution,but the increase of pressure will lead to the decrease of the density difference of saturated salt solution.And when the temperature or pressure is high,the density difference is hardly changed with other variables.Under the experimental conditions,the density difference is extremely high and extremely low two level.The main reason is that carbon dioxide does not exist supercritical state in the low temperature;and gas phase carbon dioxide can be highly compressed,in its phase change occurs when the density difference also will change rapidly.At the same time,it is found that the interfacial tension varies with the density difference under different temperature and pressure.It can be observed that the interface tension almost remains steady unless the density difference between carbon dioxide solution and salty water go beyond the restriction value of 600 kg/m3.But as the density difference increase(more than 700kg/m3),the density difference has great influence on the interfacial tension.The tension increases rapidly with the increase of the density difference.Experimental studies have shown that the relationship between temperature and pressure,the interface tension and density of the performance of roughly the same.The tension of the two phase interface can be strengthened by higher temperature whose absolute value stays relatively small and lower pressure,respectively.And because of the transition of carbon dioxide phase,the interfacial tension change will be the first intense after the trend.In the study,an increased salinity of the brine promotes the tension of the carbon dioxide-brine interface to grow.Moreover,the effects of high salinity on the interfacial tension can sweep that of temperature and pressure.The experimental data has a good fitting degree in the relationship between the increase of the interfacial tension and the salinity,and it can be proved that the interface tension is proportional to the salinity.