Intermittent gas-liquid rearrangement controls the mixing of gases in porous media.

Intermittent gas–liquid interfacial rearrangements in nitrogen injection into porous sandstone saturated with krypton and water drive distinct mixing regimes, including rapid variance decay linked to gas connectivity.

• Why it matters: Macroscopic advection–diffusion models can miss pore-scale multiphase dynamics, producing large errors in predicted gas mixing rates when gas mixing and gas–liquid redistribution occur together.
• What they did: Using 4D X-ray imaging, they tracked nitrogen injection while simultaneously measuring gas mixture composition evolution and gas–water multiphase flow in the sandstone.
• The result: Gas mixing proceeded via connectivity-controlled regimes: displacement created composition variance, intermittent rearrangements rapidly reduced it, later mixing followed confined diffusion in a quasi-static gas network, and still later was driven by multicomponent Ostwald ripening.

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