Coupled supercritical CO₂ dissolution and water flow in pore-scale micromodels

Journal Article · Fri Nov 16 00:00:00 EST 2018 · Advances in Water Resources

DOI:https://doi.org/10.1016/j.advwatres.2018.11.004· OSTI ID:1567156

Chang, Chun ^[1]; Zhou, Quanlin ^[2]; Kneafsey, Timothy J. ^[2]; Oostrom, Mart ^[3]; Ju, Yang  ^[4]

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1. China Univ. of Mining & Technology, Beijing (China); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States); INTERA, Inc, Richland, WA (United States)
4. China Univ. of Mining & Technology, Beijing (China)

Dissolution trapping is one of the most crucial mechanisms for geological carbon storage (GCS). Recent laboratory and field experiments have shown non-equilibrium dissolution of supercritical CO₂ (scCO₂) and coupled scCO₂ dissolution and water flow, i.e., scCO₂ dissolution at local pores/pore throats creating new water-flow paths, which in turn enhance dissolution by increased advection and interfacial area. Yet, the impacts of pore-scale characteristics on these coupled processes have not been investigated. In this study, imbibition and dissolution experiments were conducted under 40°C and 9 MPa using a homogeneous/isotropic hexagonal micromodel, two homogeneous elliptical micromodels with low or high anisotropy, and a heterogeneous sandstone-analog micromodel. The four micromodels, initially saturated with deionized (DI)-water, were drained by injecting scCO₂ to establish a stable scCO₂ saturation. DI water was then injected at different rates with logC_a (the capillary number) ranging from -6.56 to -4.34. Results show that bypass of scCO₂ by displacing water is the dominant mechanism contributing to the residual CO₂ trapping, triggered by heterogeneity in pore characteristics or pore-scale scCO₂-water distribution. Bypass can be enhanced by pore heterogeneity or reduced by increasing transverse permeability, resulting in relatively low (<2% of CO₂ solubility) or high (9–13% of CO₂ solubility) dissolved CO₂ concentration in displacing water. The overall dissolution of residual scCO₂ increases with decreasing C_a, and approaches to their solubility at low C_a value with sufficient residence time. This main trend is similar to a capillary desaturation curve that represents the relationship between the residual saturation and C_a. Spatially, dissolution initiates along the boundary of bypassed scCO₂ cluster(s) in a non-equilibrium manner, and the coupling of water flow and dissolution occurs which fragments the bypassed scCO₂ clusters and enhance scCO₂ dissolution.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Biological and Environmental Research (BER); National Natural Science Foundation of China (NSFC)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1567156
• Alternate ID(s): OSTI ID: 1636443
• Journal Information: Advances in Water Resources, Vol. 123, Issue C; ISSN 0309-1708
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
Geological carbon storage
Micromodel
Pore characteristics
Imbibition
CO2 dissolution
Mass transfer