Imaging and quantification of spreading and trapping of carbon dioxide in saline aquifers using meter‐scale laboratory experiments

Abstract

The role of capillary forces during buoyant migration of CO2 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 CO2 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 CO2‐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).

Characterizing Drainage Multiphase Flow in Heterogeneous Sandstones

“…(), Wei et al. () and at intermediate scales below seismic resolution (1–10 m) using meter‐scale experiments (Trevisan et al., ). Here it was explicitly shown how layered capillary heterogeneities could increase nonwetting phase trapping by up to 15% in some cases and lead to plume migration time scales of the order of months as opposed to weeks in the homogeneous case.…”

Characterising Drainage Multiphase Flow in Heterogeneous Sandstones

“…In these systems, the impact of capillary pressure heterogeneity has been demonstrated experimentally at both the core scale, i.e. Perrin and Benson (2010); Krevor et al (2011);Shi et al (2011);Wei et al (2014) and at intermediate scales below seismic resolution (1-10m) using meter-scale experiments (Trevisan et al, 2017b). Here, it was explicitly shown how layered capillary heterogeneities could increase non-wetting phase trapping by up to 15% in some cases and lead to plume migration time scales of the order of months as opposed to weeks in the homogeneous case.…”

Light hydrocarbon and noble gas migration as an analogue for potential CO2 leakage: numerical simulations and field data from three hydrocarbon systems

“…Several aspects of the modeling design in this study may have limited confidence in interpreting fluid sources. The assumptions of homogenous, isotropic, and zero‐tilt porous media and relatively large gridblocks likely overestimated CO 2 and water interaction as actual CO 2 may finger along high‐permeability pathways . As with uncertainties in rock properties, sampling from groundwater and overburden was insufficient to characterize dissolved fluids throughout the sedimentary column.…”