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The journal Water Resources Research recently published a new paper by a team that included Lluís Salo-Salgado (a 2023 ERL PhD alum who is now a postdoc at Harvard), Josimar A. Da Silva (a 2020 ERL PhD alum who is now a Research Engineer at ExxonMobil), and MIT ERL/CEE Prof. Ruben Juanes:
Assessing CO2 Migration Within Faults During Megatonne-Scale Geologic Carbon Dioxide Storage in Offshore Texas
Abstract: “Recent studies indicate that Miocene-age reservoirs offshore Texas are promising candidates for industrial-scale geologic carbon sequestration. Fault-bounded hydrocarbon traps are common, and faults may be less competent seals than the low-permeability sediments overlying the reservoirs; this means that faults may limit the amount of CO2 that can be permanently sequestered. Here, we conduct flow simulations of megatonne-scale CO2 injection next to a major, reservoir-bounding growth fault, and evaluate (a) where fault sealing capacity is exceeded, and (b) where the migrates after it enters the fault zone. We use a geologic model that includes the key structural features of fault-bounded systems near-offshore Texas, and consider both homogeneous and layered top seals (TSs). To model fault petrophysics, we apply a new, general methodology for faults in normally-consolidated, relatively shallow (depth <~3km) sequences that populates three-dimensional realizations of the fault core with sand and clay smears. We quantify uncertainty in the directional components of the fault permeability tensor and multiphase flow fault properties. We evaluate the sensitivity of fault CO2 migration to these properties, and show that the capillary entry pressure is exceeded in the lower portion of the fault. This leads to fault migration being controlled by effective fault permeability. For the cases considered, the amount of remaining in the injection formation after 1,000 years exceeds 93%, and CO2 does not migrate to depths shallower than the TS. These results suggest that, in the Miocene section, faults partially offsetting the TS do not act as preferential CO2 conduits.”
Cover image: Fault zone architecture in siliciclastic sediments. (a) Photograph from the Hambach lignite mine (Germany) by Vrolijk et al. (2016), showing a layered fault core with both sand and clay smear. (b) Photograph from Miri (Malaysia) by Sosio de Rosa et al. (2018) showing a fault core dominated by clay smear with sand lenses, and transitional footwall zone with both sand and clay smear (dashed line). (c) Schematic of a segmented normal fault, inspired by Childs et al. (2009), depicting key structural terms. In the frontal cross section, the fault cores are discontinuous across the clay to emphasize distributed deformation, rather than localization. The external envelope (dashed line) delineates the fault zone. (From the above-reference publication, CC BY-NC-ND 4.0)