Experimental study of linear and nonlinear regimes of density-driven instabilities induced by CO2 dissolution in water

R Outeda,A Zalts,C El Hasi,A D'Onofrio

doi:10.1063/1.4868040

Abstract

Density driven instabilities produced by CO2 (gas) dissolution in water containing a color indicator were studied in a Hele Shaw cell. The images were analyzed and instability patterns were characterized by mixing zone temporal evolution, dispersion curves, and the growth rate for different CO2 pressures and different color indicator concentrations. The results obtained from an exhaustive analysis of experimental data show that this system has a different behaviour in the linear regime of the instabilities (when the growth rate has a linear dependence with time), from the nonlinear regime at longer times. At short times using a color indicator to see the evolution of the pattern, the images show that the effects of both the color indicator and CO2 pressure are of the same order of magnitude: The growth rates are similar and the wave numbers are in the same range (0-30 cm(-1)) when the system is unstable. Although in the linear regime the dynamics is affected similarly by the presence of the indicator and CO2 pressure, in the nonlinear regime, the influence of the latter is clearly more pronounced than the effects of the color indicator.

Highlights

The interest on instabilities in flows has focused on a broad scope of phenomena, such as assisted oil recovery, combustion, electrochemical depositions, reactive-diffusive systems, etc
The images were analyzed and instability patterns were characterized by mixing zone temporal evolution, dispersion curves, and the growth rate for different CO2 pressures and different color indicator concentrations
The main point of these results is that in the experiments done at short times using a color indicator to see the evolution of the pattern, the dynamics is affected by the presence of the indicator, but it has negligible effects at long times compared with the influence of CO2 pressure

Summary

Introduction

The interest on instabilities in flows has focused on a broad scope of phenomena, such as assisted oil recovery, combustion, electrochemical depositions, reactive-diffusive systems, etc. In assisted oil recovery, water is used to produce the movement of oil as water has a lower viscosity than oil, viscous fingering is produced affecting the dynamics of the system.. In deep geologic CO2 sequestration, density driven instabilities can be expected: CO2 is a soluble and reactive gas in water. Once it enters the aqueous phase, there is a density increase below the water surface because of the dissolution of the gas. Chemical reactions in the aqueous phase can affect the instabilities triggered by density increases

Results

Discussion

Conclusion