Speaker
Description
Numerical simulations are essential for understanding the migration and trapping of injected CO2 in saline aquifers. They allow to predict plume spreading, CO2 dissolution, leakage rates and assess possible risks and pitfalls in the process. However, their predictive capability depends on detailed and accurate knowledge of subsurface properties, and in particular the type and degree of heterogeneity, which is often incomplete. Here, we investigate the effect of spatial heterogeneity on the migration and trapping of CO2 in geologic carbon storage. We perform 2-D numerical simulations of CO2 injection and consequent spreading into aquifers having uncorrelated (random) and spatially-correlated heterogeneous permeability fields of different correlation lengths, using parameters from a potential storage site, the Negev Jurassic aquifer (Israel). We analyze the plume shape, leakage rates and the degree of trapping in the different scenarios.
We find that the type of heterogeneity significantly affects the dynamics of the CO2 plume spreading: in the homogeneous and uncorrelated cases, the CO2 plume rises rapidly and then spreads horizontally as a thin plume beneath the caprock. In the correlated cases, however, the plume remains in the bottom of the aquifer (further down from the caprock), where the plume primarily migrates horizontally, exhibiting a larger lateral spreading with increasing correlation length. Yet, the horizontal extent of the plume in the correlated cases remains smaller than in the homogeneous and uncorrelated cases. Consequently, in the correlated cases, CO2 does not reach the caprock throughout the duration of the simulation, while in the homogeneous and uncorrelated cases, a negligible fraction of the CO2 penetrates into the caprock in the form of dissolved CO2. Heterogeneity, regardless of spatial correlation, increases the fraction of trapped CO2 (dissolved CO2 and capillary-trapped CO2), and therefore the storage security.
In conclusion, we show that correlated heterogeneity substantially increases storage security and decreases risk of leakage, by keeping the CO2 plume away from the caprock and increasing CO2 trapping. Our study highlights the importance of detailed characterization of heterogeneity structure in sites that are considered for CO2 storage.
| Country | Israel |
|---|---|
| Water & Porous Media Focused Abstracts | This abstract is related to Water |
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