Geometry evolution in dissolving microfluidic rough fractures_Figshare.xlsx

Dissolution front or water-rock interface influenced by reactive flow in rock fractures is closely related to many complex geochemical processes, including leakage of CO2 sequestration, stimulation of petroleum reservoirs and formation of karst systems. The flow rate and surface roughness, which determines the flow and transport regimes in rough fracture, is a critical factor for improving our understanding and prediction of flow and transport in fractures. However, the relation between flow rate and dynamic evolution of dissolution front in rough fractures is not well understood. Here, real-time imaging experiments on microfluidic fractures equipped with dissolving sodium chloride crystal chip have been performed on flow visualization system. We observe that smooth effect occurs when reactive fluid flow through rough fractures. Small scale roughness, characterized by secondary surface roughness factor (SRF2), decreased rapidly and large scale undulation, characterized by primary surface roughness factor (SRF1), decreased gradually during dissolution process. By varying volume flow rate Q systematically, we find that the overall dissolution rate and dissolution patterns strongly rely on the Péclet number, which measures the relative magnitude of advective and diffusive transport of the solute. Overall dissolution rate is increasing at early stage due to smooth effect and stable at later stage under various Pe conditions. Dissolution patterns of fracture channels vary from wedge dissolution to uniform dissolution as Péclet number increases. Theoretical analysis to distinguish wedge dissolution pattern and uniform dissolution pattern is in agreement with experimental observations.