A generalized theory of Ostwald ripening in porous media
Research Poster Engineering 2025 Graduate ExhibitionPresentation by Nicolas Bueno Zapata
Exhibition Number 110
Abstract
In many engineering applications, bubbles trapped in a porous medium can dissolve into the wetting phase, undergoing Ostwald ripening, a process where mass is transferred from high- to low-interfacial curvature bubbles. Unlike bulk fluids, in which a single large bubble remains at equilibrium, stable configurations of multiple bubbles with different sizes can emerge in a porous medium due to the non-monotonic relationship between curvature and bubble size. This in turn can impact the storage capacity and hydraulic conductivity of the pore space in applications such as carbon sequestration and geologic hydrogen storage. Theories that reliably predict this evolution in bubble sizes are limited to spherical bubbles, either in bulk fluids or trapped inside homogeneous porous microstructures. We present a new kinetic theory that applies to non-spherical bubbles in heterogeneous porous media with possible spatial correlations in pore sizes. Our theory describes the temporal evolution of bubble statistics through a population balance equation that is closed through first principles at the pore scale. We validate the theory against pore network simulations and identify areas for further research. The work constitutes a key step towards predictions of multicomponent ripening.
Importance
Achieving net-zero CO2 emissions by 2050 requires hydrogen production from cleaner energy sources and CO2 capture from the atmosphere. Both processes depend on injecting large volumes of gas into underground geologic formations, where the gas exists as bubbles surrounded by water. These bubbles deform due to the porous structure, changing in size over space and time. This pore-scale phenomenon controls gas storage capacity and mobility at larger scales. Our theory enables precise prediction of bubble evolution, providing crucial insights for optimizing subsurface gas storage. Furthermore, it closes a gap to advance large-scale hydrogen production, reducing long-term dependence on fossil fuels.