Trapping of carbon in deep underground brine-filled reservoirs is a promising approach for the reduction of atmospheric greenhouse gas emissions. However, estimation of the amount of carbon dioxide (CO2) that can be captured in a reservoir remains a challenge. One difficulty lies in the estimation of local capillary pressure effects that arise from mineral surface heterogeneity inherent in underground geological formations. As a preliminary step to address this issue, we present a series of pore network modeling (PNM) simulations of two-phase immiscible flow in 3D structured porous media with contact angle heterogeneity. We present saturation patterns for networks with homogeneous and heterogeneous wettability under typical reservoir conditions, taking into account varying contact angles for CO2 on mica and quartz at supercritical conditions. At lower flow rates, our preliminary results showed higher saturations for the heterogeneous networks than for the homogeneous ones. To characterize the fingering patterns, we have introduced R as the ratio of filled throats to the total network saturation. Based on this measure, the heterogeneous networks demonstrated thicker fingering patterns than the homogeneous networks. These preliminary results highlight the importance of micro-scale surface heterogeneity for the modeling of carbon storage processes.

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