Dynamics of buoyancy driven miscible iso-viscous flows in heterogeneous layered porous media

Buoyancy-driven instabilities in horizontally layered heterogeneous porous media are investigated using numerical simulations. The analysis is conducted for two different permeability distributions, where the permeability attains its maximum (minimum) at the initial interface. The effects of the frequency of layers ( q) and variance of the permeability distribution ( s) under different scenarios of density mismatches were analyzed and characterized both qualitatively and quantitatively. Results revealed that heterogeneity induces undulated more diffuse finger structures compared to the homogeneous case. In cases where the permeability at the initial interface is maximum, it is found that the larger the q , the less unstable the flow. It is shown that the onset time of the instability increases with increasing number of layers and decreases with increasing heterogeneity variance. Moreover, it is revealed that flow mixing increases (decreases) with increasing heterogeneity variance before (after) a critical flow time. The trends observed are, however, reversed in the case of shifted permeability heterogeneity where the smallest permeability is at the initial interface. Interestingly, it was found that for the shifted permeability distribution, an unstable flow in a homogeneous medium can be fully stabilized when a small number of layers are used in the heterogeneous case.