4D tomography reveals a complex relationship between wormhole advancement and permeability variation in dissolving rocks

Dissolution of porous media induces positive feedback between fluid transport and chemical reactions at mineral surfaces, leading to the formation of wormhole-like channels within the rock. Wormholes provide highly efficient flow and transport paths within rock, and as such, understanding their formation is critical for controlling contaminant migration or preventing CO2 leakage during geological carbon sequestration. Here, using time-resolved X-ray tomography, we capture the dynamics of wormhole propagation, inaccessible by standard experimental methods. We find a highly non-trivial relationship between wormhole advancement and variations in permeability of the rock, with extensive periods of steady advancement not reflected by significant change in permeability. This is in contrast to most existing conceptual models where wormholes advance in a linear fashion. We show that this is caused by the presence of highly cemented regions which act as barriers to flow, as confirmed by multi-scale analysis of the pore geometry based on tomographic, (ultra) small angle neutron scattering, and optical microscopy measurements. These results demonstrate that time-lapse captured wormhole dynamics can be used to probe the internal structure of the rock.