Onset of Convective Instability in a Porous Medium with a Low-Permeability Layer

This study presents an investigation on the stability of a diffusive boundary layer in a heterogeneous system comprising a porous medium with an embedded low-permeability layer in the context of geological sequestration of CO2. The increasing atmospheric CO2 provides a basis for CO2 injection into a deep saline aquifer. Saline aquifer formation, commonly found in sedimentary basin, occurs naturally as layers of distinguishable depositional facies. Many previous studies on convective instability in heterogeneous porous system are based on random and regular variation of permeability. The effect of a layered permeability heterogeneity on the onset of convective instability has been considered with a steady base profile. However, the role of a layered permeability heterogeneity on the onset of convective instability with diffusive base profile has not received much attention. This study on density driven convective instability is based on Linear stability analysis with quasi-steady state approximation. Finite difference numerical framework is adopted to handle the stepwise change in the permeability field. Our results are validated against previous studies for homogeneous and smoothly varying permeability. We observed that the onset of convective instability depends non-monotonically on the presence of a low-permeability layer.