Pore-scale Observations of Salt Precipitation using Microfluidics*

This study is motivated by the challenging needs for unraveling the pore-scale dynamics and under-lying mechanisms of salt precipitation, a potential threat that hinders the processes of Carbon Capture and Storage (CCS) in deep saline aquifers. We experimentally investigate the influences of pore-structure and brine concentration on the drying rate of brine and subsequent salt precipitation using microfluidics. Three distinct precipitation stages are observed: (I) initial, (II) rapid growth, and (II) final phases, corresponding to the changing brine drying rate respectively. Considerable local salt precipitation formed in the rapid-growth period connects with large pools of residual brine, providing ion source for extended salt nucleation. In addition, the salt-precipitation speeds during the second phase are linearly dependent on the brine-drying rate. These result would help estimate the total amount and the spreading rate of salt precipitation for different brine-drying rates.