Pore- and Core-Scale Supercritical CO2 Dissolution and Mass Transfer under Drainage and Imbibition Conditions
Abstract
In modeling of geological carbon storage, dissolution of supercritical CO2 (scCO2) is often assumed to be instantaneous with equilibrium phase partitioning. Recent core- and pore-scale experimental studies have shown that scCO2-water displacement (drainage and imbibition) is significantly affected by sub-core and pore-scale heterogeneity. The non-equilibrium scCO2 dissolution and mass transfer are expected when preferential flow and non-uniform distribution between water and scCO2 prevail due to core- and pore-scale heterogeneity. We conducted a series of pore- and core-scale scCO2 dissolution experiments at supercritical conditions (8-10 MPa and 40-45 °C) in (1) two heterogeneous sandstone cores and (2) four micromodels representing typical pore characteristics of porous media with varying homogeneity, heterogeneity, anisotropy and pore shapes. scCO2 dissolution and mass transfer under drainage and imbibition conditions at both scales were investigated under displacement rates with (the capillary number) from -7.0 to -4.0. We show the dsCO2 (dissolved CO2) concentrations in the effluent water range from 0.05 to 60% of CO2 solubility. The pore-scale experiments provide direct evidence and images on this non-equilibrium dissolution. Under the various experimental conditions at both pore and core scales, equilibrium dissolution cannot be reached because of the limited scCO2-water interface area available for CO2 dissolution and limited residence time for dsCO2 mass transfer. Pore-scale experiments also show the coupled scCO2 dissolution and water flow, i.e., scCO2 dissolution at local pores/pore throats creates new water-flow paths, which in turn enhances dissolution by additional advection and interfacial area. A diagram with all data from this study and selected data from previous literatures shows that (1) the concentration of dsCO2 increases with the decrease in (i.e., the increase in water resident time), and only approaches to their solubility with sufficient residence time, and (2) this main trend is secondarily affected by the coupled scCO2 dissolution and water flow that depend on limited or pervasive water-flow paths in the regime of non-equilibrium dissolution.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H41K2221C
- Keywords:
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- 1832 Groundwater transport;
- HYDROLOGYDE: 1859 Rocks: physical properties;
- HYDROLOGYDE: 1878 Water/energy interactions;
- HYDROLOGYDE: 1895 Instruments and techniques: monitoring;
- HYDROLOGY