Pore-network modeling of Ostwald ripening in porous media: How do trapped bubbles equilibrate?

Ostwald ripening of trapped bubbles in porous media is relevant to several subsurface (e.g., CO2 storage) and manufacturing (e.g., fuel cells) applications. A fundamental question common to both is: how does an initially heterogeneous distribution of bubble sizes, PDFo, evolves towards a stable equilibrium distribution, PDFe? And what is PDFe? We develop a pore-network model (PNM) that simulates the temporal evolution of a partially miscible population of bubbles from PDFo to PDFe. The PNM is validated against published micromodel experiments. We subsequently propose a theory that can predict PDFe directly. The predictions are compared against PNM simulations and found to be in close agreement. Using the PNM, we also show that bubble equilibration in heterogeneous porous media is a lot slower than homogeneous media. Limitations and potential extensions of both the PNM and the theory are discussed. (C) 2022 Elsevier Inc. All rights reserved.

Automated summary

This article investigates the Ostwald ripening of trapped bubbles in porous media, which is relevant to subsurface and manufacturing applications. Through simulations and theoretical analysis, the article reveals the evolution process of the bubble size distribution from initially non-uniform to stable equilibrium, and finds that the equilibration of bubbles in heterogeneous porous media is slower than in homogeneous media.