Preprints
https://doi.org/10.22541/au.170709021.19680723/v1
https://doi.org/10.22541/au.170709021.19680723/v1
25 Nov 2024
 | 25 Nov 2024
Status: this preprint is open for discussion.

Numerical Analysis of the Effect of Heterogeneity on CO2 Dissolution Enhanced by Gravity Driven Convection

Yufei Wang, Daniel Fernandez Garcia, and Maarten W. Saaltink

Abstract. Dissolution trapping of CO2 in brine can mitigate the risk of supercritical CO2 leakage during long-term Geological Carbon Sequestration (GCS). The dissolution of overlying supercritical CO2 into brine increases the density of brine in its upper portion, which causes Gravity-Driven Convection (GDC) and thus significantly increases the rate of CO2 dissolution. To date, most studies on GDC-driven dissolution are based on homogeneous media and only few studies exist on the effect of heterogeneity on GDC-driven dissolution. Here, we study the effect of heterogeneity and anisotropy on GDC-driven dissolution rate by using numerical simulations with randomly obtained permeability fields. Dissolution rates calculated by these simulations are related to properties of the permeability field by using least-squares regression. We obtained two empirical formulas for predicting the asymptotic GDC-driven dissolution rate. In the first formula the dissolution rate is almost linearly proportional to the dimensionless equivalent vertical permeability. In the second one the dissolution rate is linearly proportional to a dimensionless vertical finger-tip velocity. This indicates that the GDC-driven dissolution can be predicted using either the equivalent vertical permeability or the vertical finger-tip velocity. Furthermore, both formulas demonstrate that higher anisotropy results in lower dissolution rates, suggesting that pronounced horizontal stratification can inhibit the dissolution of CO2.

Yufei Wang, Daniel Fernandez Garcia, and Maarten W. Saaltink

Status: open (until 06 Jan 2025)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
Yufei Wang, Daniel Fernandez Garcia, and Maarten W. Saaltink
Yufei Wang, Daniel Fernandez Garcia, and Maarten W. Saaltink

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Short summary
During geological carbon sequestration, the injected supercritical CO2, being less dense, floats above the brine. The dissolution of CO2 into brine helps mitigate the risk of CO2 leakage. As CO2 dissolves into the brine, it increases the density of brine in the upper layer, initiating gravity-driven convection (GDC), which significantly enhances the rate of CO2 dissolution. We derived two empirical formulas to predict the asymptotic dissolution rate driven by GDC in heterogeneous fields.