Brine Drying and Salt Precipitation in Porous Media: A Microfluidics Study

Drying and salt precipitation in porous media impact various engineering disciplines, including carbon geological storage in brine reservoirs, with considerable hydraulic and mechanical effects. However, understanding the underlying mechanisms and controlling factors is limited due to the lack of pore-scale observation and quantitative analysis. We design radial flow microfluidic chips with varying pore heterogeneity and wettability and quantify the pore-scale dynamics of brine drying and salt precipitation using time-lapse images and image processing techniques. The gas injection process determines the distribution of residual (drying) brine and is influenced by pore heterogeneity. Higher concentrations of residual brine are observed near the injection well in more heterogeneous porous media. Capillary backflow replenishes evaporative losses near the well during drying in hydrophilic chips. Brine clusters induced by gas injection connect through brine films and reconnect by capillary backflow. Two types of pore habits of salt precipitation are identified: bulk salt within brine clusters and aggregated salt at the air-brine interface. Salt precipitation, particularly near the injection well, significantly reduces injectivity, with less impact observed in the porous media with uniform pore structure and hydrophobic surfaces. Brine drying and salt precipitation dynamics were quantified in radial-flow microfluidicsCapillary backflow in hydrophilic chips induced significant salt precipitation near the injection wellHigher pore heterogeneity led to increased near-well residual brine and salt precipitation