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Imaging and quantification of spreading and trapping of carbon dioxide in saline aquifers using meter‐scale laboratory experiments
Author(s) -
Trevisan Luca,
Pini Ronny,
Cihan Abdullah,
Birkholzer Jens T.,
Zhou Quanlin,
GonzálezNicolás Ana,
Illangasekare Tissa H.
Publication year - 2017
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1002/2016wr019749
Subject(s) - plume , buoyancy , imbibition , saturation (graph theory) , aquifer , carbon sequestration , capillary action , geology , soil science , porous medium , carbon dioxide , mineralogy , mechanics , hydrology (agriculture) , environmental science , groundwater , chemistry , geotechnical engineering , porosity , materials science , meteorology , composite material , botany , physics , germination , mathematics , organic chemistry , combinatorics , biology
The role of capillary forces during buoyant migration of CO 2 is critical toward plume immobilization within the postinjection phase of a geological carbon sequestration operation. However, the inherent heterogeneity of the subsurface makes it very challenging to evaluate the effects of capillary forces on the storage capacity of these formations and to assess in situ plume evolution. To overcome the lack of accurate and continuous observations at the field scale and to mimic vertical migration and entrapment of realistic CO 2 plumes in the presence of a background hydraulic gradient, we conducted two unique long‐term experiments in a 2.44 m × 0.5 m tank. X‐ray attenuation allowed measuring the evolution of a CO 2 ‐surrogate fluid saturation, thus providing direct insight into capillarity‐dominated and buoyancy‐dominated flow processes occurring under successive drainage and imbibition conditions. The comparison of saturation distributions between two experimental campaigns suggests that layered‐type heterogeneity plays an important role on nonwetting phase (NWP) migration and trapping, because it leads to (i) longer displacement times (3.6 months versus 24 days) to reach stable trapping conditions, (ii) limited vertical migration of the plume (with center of mass at 39% versus 55% of aquifer thickness), and (iii) immobilization of a larger fraction of injected NWP mass (67.2% versus 51.5% of injected volume) as compared to the homogenous scenario. While these observations confirm once more the role of geological heterogeneity in controlling buoyant flows in the subsurface, they also highlight the importance of characterizing it at scales that are below seismic resolution (1–10 m).