Bubble Coarsening Kinetics in Porous Media

Abstract

Bubbles in subsurface porous media spontaneously coarsen to reduce free energy. Bubble coarsening dramatically changes surface area and pore occupancy, which affect the hydraulic conductivity, mass and heat transfer coefficients, and chemical reactions. Coarsening kinetics in porous media is thus critical in modeling geologic CO2 sequestration, hydrogen subsurface storage, hydrate reservoir recovery, and other relevant geophysical problems. We show that bubble coarsening kinetics in porous media fundamentally deviates from classical Lifshitz-Slyozov-Wagner theory, because porous structure quantizes the space and rescales the mass transfer coefficient. We develop a new coarsening theory that agrees well with numerical simulations. We identify a pseudo-equilibrium time proportional to the cubic of pore size. In a typical CO2 sequestration scenario, local equilibrium can be achieved in 1s for media consisting of sub-micron pores, while in decades for media consisting of 1 mm pores. This work provides new insights in modeling complex fluid behaviors in subsurface environment.