Carbon Dioxide Plume in Bespoke 2D Porous Micromodels

Niloy De (1) , Patrice Meunier (2) , Yves Méheust (3) , François Nadal (1)

1 Loughborough University
2 IRPHE - Institut de Recherche sur les Phénomènes Hors Equilibre
3 GR - Géosciences Rennes

In the current context of global warming, the short-term mitigation of greenhouse gas emission isof utmost importance. In this context, geological storage of carbon dioxide (CO2) appears a promisingsolution. Upon injection, supercritical CO2rises up to the top caprock and immediately starts dissolvingat the water/brine interface, leading to a CO2-enriched layer of brine that happens to be heavier thanthe underlying pure brine. After a diffusion stage, this unstable configuration triggers a gravitationalinstability where convective plumes are generated and pour downwards to the bottom of the aquifer.In such a convective regime, the dissolution rate of CO2- that is the efficiency of the CO2-trapping -is greatly enhanced. However, the trapping efficiency is drastically affected by dispersion and mixingeffects occurring at the porous scale [1, 2, 3].In this work, experiments are performed to study the CO2plume migration by means of in-housebuilt microfluidic micromodels (pseudo Hele-Shaw cells). The micromodel core is made of NOA-63 ,a UV curable photo resin which is impermeable to gases. We developed a soft-lithography repeatableprotocol to make symmetric regular patterns of cylindrical pillars sandwiched between two vertical planewalls separated from each other by a 300μm gap. Pillars diameters ranging fromR= 200 to 400μm,and edge-to-edge distances (between pillars) ranging fromRto 4Rhave been tested.The water-filled micromodel was placed vertically in a CO2-pressurized chamber, and plumes werevisualized usingpH -sensitive colour indicators - since CO2-dissolution increases the acidity of aqueoussolutions. We have used Bromocresol Purple (BP) whose color change region lies between 6.8 and 4.8units ofpH . The partial pressure of CO2ranging from 1 to 8 bar have been explored. We observedthat lateral growth of the gravitational fingers is enhanced by porous dispersion, which in turn reducestransverse concentration gradients in the system. This leads to decreases the growth rate of the instability(for a given value of the permeability) and mitigates the dissolution rate of carbon dioxide - i.e. thequantity of CO2dissolved in the liquid per unit time (Sherwood number)

Domaines: Mécanique des fluides [physics.class-ph]

Niloy De, Patrice Meunier, Yves Méheust, François Nadal. Carbon Dioxide Plume in Bespoke 2D Porous Micromodels. Interpore 2020, Aug 2020, En ligne, Netherlands. ⟨insu-02929537⟩