2021/10/08 by Christophe Brouzet, Brouzet, Christophe, Yves Méheust +3
Engineering · Environmental Science · #Atmospheric and Environmental Gas Dynamics #CO2 Sequestration and Geologic Interactions #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Geophysics (physics.geo-ph) #Hydrocarbon exploration and reservoir analysis #Methane Hydrates and Related Phenomena
paper · pdf · doi:10.48550/arxiv.2110.03962
openalex publication_date 2021/10/08 · openalex created_date 2022/07/25 · openalex updated_date 2026/07/28
Geological storage of CO2 in deep saline aquifers is a promising measure\nto mitigate global warming by reducing the concentration of this greenhouse gas\nin the atmosphere. When CO2 is injected in the geological formation, it\ndissolves partially in the interstitial brine, thus rendering it denser than\nthe CO2-devoid brine below, which creates a convective instability. The\nresulting convection accelerates the rate of CO2 perennial trapping by\ndissolution in the brine. The instability and resulting convection have been\nintensively discussed by numerical and theoretical approaches at the Darcy\nscale, but few experimental studies have characterized them quantitatively. By\nusing both refractive index matching and planar laser induced fluorescence, we\nmeasure for the first time the onset characteristics of the convective\ndissolution instability in a 3-D porous medium located below a gas compartment.\nOur results highlight that the dimensional growth rate of the instability\nremains constant when the CO2 partial pressure in the compartment is varied,\nin clear discrepancy with the theoretical predictions. Furthermore, within the\nCO2 partial pressure range studied, the measured growth rate is 1 to 3\norders of magnitude larger than the predicted value. The Fourier spectrum of\nthe front is very broad, highlighting the multi-scale nature of the flow.\nDepending on the measurement method and CO2 partial pressure, the mean\nwavelength is 1 to 3 times smaller than the predicted value. Using a\ntheoretical model developed recently by Tilton (J.~Fluid Mech., 2018), we\ndemonstrate that our experimental results are consistent with a forcing of\nconvection by porosity fluctuations. Finally, we discuss the possible effects\nof this forcing by the porous medium's pore structure on the CO2 flux across\nthe interface, measured in our experiments about one order of magnitude higher\nthan expected.\n