Modeling Commercial-Scale CO₂ Storage in the Gas Hydrate Stability Zone with PFLOTRAN v6.0

Abstract. Safe and secure carbon dioxide (CO₂) storage is likely to be critical for mitigating some of the most dangerous effects of climate change. In the last decade, there has been a significant increase in activity associated with reservoir characterization and site selection for large-scale CO₂ storage projects across the globe. These prospective storage sites tend to be terrestrial sites selected for their optimal structural, petrophysical, and geochemical trapping potential. However, it has also been suggested that storing CO₂ in reservoirs within the gas hydrate stability zone (GHSZ), characterized by high pressures and low temperatures (e.g., Arctic or marine environments), could provide natural thermodynamic and solubility barriers to gas leakage. Evaluating the prospect of commercial-scale, long-term storage of CO₂ in the GHSZ requires reservoir-scale modelling capabilities designed to account for the unique physics and thermodynamics associated with these systems. We have developed the HYDRATE flow mode and accompanying fully implicit parallel well model in the massively parallel subsurface flow and reactive transport simulator PFLOTRAN to model CO₂ injection into the marine GHSZ. We have applied these capabilities to a set of CO₂ injection scenarios designed to reveal the challenges and opportunities for commercial-scale CO₂ storage in the GHSZ.