Abstract
Most numerical simulation studies have focused on the effect of homogenous wettability on fluid flow dynamics; however, most rocks display spatially heterogeneous wettability. Therefore, we have used direct numerical simulations (DNS) to investigate wettability heterogeneity at pore-scale. We have built a quasi-3D pore-scale model and simulated two-phase flow in a homogenous porous media with homogenous and heterogeneous wettability distributions. Five different heterogeneous wettability patterns were used in this study. We observed that heterogenous wettability significantly affects the evolution of fluid interface, trapped saturation, and displacement patterns. Wettability heterogeneity results in fingering and specific trapping patterns which do not follow the flow behaviour characteristic of a porous medium with homogenous wettability. This flow behaviour indicates a different flow regime that cannot be estimated using homogenous wettability distributions represented by an average contact angle. Moreover, our simulation results show that certain spatial configurations of wettability heterogeneity at the microscale, e.g. being perpendicular to the flow direction, may assist the stability of the displacement and delay the breakthrough time. In contrast, other configurations such as being parallel to the flow direction promote flow instability for the same pore-scale geometry.
Highlights
Most numerical simulation studies have focused on the effect of homogenous wettability on fluid flow dynamics; most rocks display spatially heterogeneous wettability
We present the key results from the numerical simulations, focusing on the effect of homogeneous and heterogeneous contact angle distribution on pore-filling events, trapped saturations and displacement patterns
We have investigated the influence of surface wetting properties and wettability heterogeneity on the two-phase flow of air and water at the pore-scale using direct numerical simulations
Summary
Most numerical simulation studies have focused on the effect of homogenous wettability on fluid flow dynamics; most rocks display spatially heterogeneous wettability. We have built a quasi-3D pore-scale model and simulated two-phase flow in a homogenous porous media with homogenous and heterogeneous wettability distributions. Wettability heterogeneity results in fingering and specific trapping patterns which do not follow the flow behaviour characteristic of a porous medium with homogenous wettability. This flow behaviour indicates a different flow regime that cannot be estimated using homogenous wettability distributions represented by an average contact angle. The effect of wettability is usually incorporated in numerical reservoir simulations via flow functions, known as relative permeability (kr) and capillary pressure (Pc) curves obtained from laboratory measurements of core samples
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