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.