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Transport of Groundwater, Heat, and Radiogenic He in Topography‐Driven Basins

Han, Weon Shik, Kim, Kue‐Young, Jung, Na‐Hyun, Park, Eungyu, Solomon, D.K.
Ground water 2015 v.53 no.S1 pp. 33-46
basins, groundwater, groundwater flow, heat, helium, sodium chloride, solutes, temperature profiles
The goal of the study is to assess the feasibility of characterizing the caprock integrity by utilizing sampled helium (He) concentration in fluids and temperature measurement prior to CO₂injection. A series of simulations representing pre‐CO₂injection phase was conducted to reveal the spatial distribution of groundwater, temperature, and He concentration under various geologic conditions of topographically driven basin. Then, their profiles in preinjection conditions were compared with dynamic signatures of both injection‐induced pressure and leaked brine concentration at post‐CO₂injection conditions. In the topographic basin, He and heat transports generally show analogous transport except the low‐permeability basin where the conductive heat and diffusive solute transports are the primary transport mechanisms. The transition occurred at permeabilities between 10⁻¹⁵and 10⁻¹⁴ m². Inclusion of low‐k layer (low‐k layer: 10⁻¹⁶ m²and surrounding basin: 10⁻¹³ m²) segregates shallow and deep groundwater system and creates a 3‐km single large free convection of groundwater driven by unevenly distributed thermal profile of basin. Finally, He and temperature profiles with high‐k pathways at pre‐CO₂injection scenarios and NaCl mass fractions at post‐CO₂injection showed systematic trends and relationships, suggesting that proper understanding of these trends will aid to identify the seal integrity.