Speaker
Description
Partially miscible bubbles trapped within porous media occur in numerous applications, including geologic CO₂ sequestration, groundwater remediation, fuel cells, and most notably underground hydrogen storage (UHS). In UHS, hydrogen is cyclically injected and withdrawn – pre-charged by a cushion gas (e.g., CO₂) – generating trapped bubbles with distributions of sizes and compositions. Differences in curvature and composition between bubbles drive mass exchange by molecular diffusion, a process called Ostwald ripening. This causes gradual evolution toward thermodynamic equilibrium that affects the spatial distribution of bubbles, and thus the hydraulic properties of the rock. Ostwald ripening is well-studied in bulk fluids but only beginning to be understood in porous media, where confinement enables multiple bubbles to coexist at equilibrium. This talk will discuss how to describe evolving bubble populations theoretically using a novel statistical formulation that tracks the number-density of bubble states through time. We will review prior theoretical work for single-component ripening building on the famed Lifshitz-Slyozov-Wagner theory of bulk fluids, then offer an extension to multicomponent bubble populations subject to confinement of a porous medium. Bubble deformation, pore-size heterogeneity, and spatial correlations are captured. The theory provides a path forward to upscaling and predicting macroscopic properties like hydraulic conductivity, storage capacity, purity loss, and leakage, while revealing outstanding challenges.
| Country | United States |
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