Observation of Brine Backflow and Salt Precipitation during Brine Drying in Fractured Porous Media

Summary This research examines the evaporation of brine in fractured porous media due to CO2 gas injection, with a focus on the dynamic relationship between brine evaporation, advection, and diffusion. The uneven evaporation in fractured systems leads to spatial differences in the Peclet (Pe) number, representing the ratio between advective and diffusive transport. Under water-wet conditions, brine initially resides in the smaller pores, while gas flows preferentially through the larger pores and fracture pathways. As evaporation progresses, pressure gradients generate capillary forces that draw brine from smaller pores into fractures and larger pore spaces, sustaining evaporation and promoting salt crystallization within the fractures. Experimental findings reveal that Pe values are significantly higher in fractures, indicating that advection dominates the transport processes, which enhances capillary backflow and accelerates salt accumulation. This buildup of salt suggests potential for fracture self-sealing, as the precipitated salts can obstruct flow pathways. These insights deepen our understanding of the coupled processes of brine evaporation, capillary backflow, and salt precipitation, offering valuable implous syications for the management of fractured porstems in geological and engineering applications.