Coupled permeability–thermal conductivity framework for global reservoir suitability assessment of carbon dioxide hydrate-based carbon sequestration

Subsea sediments may provide a promising pathway for carbon neutrality by storing carbon dioxide as solid hydrate. Here we use a self-developed numerical multiphysics simulator to examine hydrate-based carbon storage over 100,000 years, capturing coupled multiphase flow, heat transfer and phase transitions in marine sediments. The sequestration process can be divided into three sequential stages. Under the homogeneous baseline model and reference injection schedule, the theoretical single-well storage capacity is estimated to be 41,975 tonnes of liquid carbon dioxide while maintaining the prescribed safety criterion. Permeability enhances early-stage storage at higher values but reduces vertical buffering. High thermal conductivity restores temperatures more rapidly to hydrate-stable conditions, increasing storage efficiency and safety margins. A two-parameter map integrating permeability and thermal conductivity identifies distinct storage regimes and helps screen offshore reservoirs for safe and efficient carbon dioxide sequestration. Carbon dioxide stored as solid hydrate remains stable for one hundred thousand years, with storage capacity and safety strongly controlled by sediment permeability and thermal conductivity, according to multiphysics simulator of flow heat and phase change.