Effect of Nonlinear Reaction on Miscible Gravitational Instability through Dispersive Porous Medium

Abstract

Gravitational instability in porous media is observed in numerous natural systems in which reaction at the penetrating chemical front is a common occurrence. Most often, this reaction kinetics is difficult to capture and explain adequately using the classical linear reaction rate profiles.The nonlinearity of the reaction rate addresses the general reaction framework that may be encountered in natural settings and has substantial ramifications for the overall gravitational instability dynamics at long times. However, the way in which a nonlinear reaction affects the dissolution in combination with porous dispersion has remained largely elusive. This study used a two-dimensional (2D) numerical framework built in OpenFOAM to capture the coupled effect of nonlinear reaction kinetics and porous dispersion on the ensuing gravitational instability across a miscible fluid pair. This study quantitatively explored the instability onset times, total dissolution of heavier fluid, and convective dynamics as a function of the nonlinearity in the chemical kinetics in dispersive porous media. We hereby report intriguing and nonintuitive effects on induced gravitational instability in the presence of nonlinear chemical reactions. The results show a decrease in the nonlinear onset time and increase in overall dissolution with stronger reaction rate. The onset time and overall dissolution varied with the nonlinearity of the reaction kinetics. This study focused on the enhancement of effective dissolution employing the inherently occurring chemical reactions in natural systems, and is a model tool to understand various geological reaction-transport and sequestration phenomena.