Microfluidic Study of Evaporation-Driven Crystallization of Saline and Ammonia Brines under Hydrogen Flow

This study explores the crystallization dynamics, fluid mobility, and interfacial behavior of various saline and multicomponent fluids in a microfluidic platform mimicking porous subsurface environments. Using a custom-designed chip and flow system, we investigate how different brine compositions—including NaCl solutions, surfactant-modified mixtures, alcohol-water blends, and ammonia-rich fluids—respond under varying flow conditions, focusing on the onset and evolution of salt precipitation. Microscopic observations and quantitative analysis reveal that while higher flow rates accelerate brine evaporation and crystal nucleation.

We highlight that capillary-driven transport between adjacent brine pools plays a dominant role in localized crystallization, with ionic additives such as K⁺ and OH⁻ further accelerating salt growth and increasing clogging potential. The influence of physicochemical properties, particularly volatility and interfacial tension, is evident—where reduced IFT and increased fluid volatility (via surfactants or alcohols) consistently lead to a lower risk of clogging. In contrast, ammonia-containing solutions demonstrate rapid and extensive crystal formation due to H2-induced precipitation of ammonium bicarbonate, independent of brine evaporation. This underscores the importance of understanding complex fluid-rock interactions, especially in multicomponent systems where non-NaCl crystallization pathways may dominate.