Spatial differences in pressure and heat transfer characteristics of CO2 hydrate with dissociation for geological CO2 storage

The submarine CO2 hydrate-based geological storage is an effective method for carbon capture and storage, which is significant for mitigating the greenhouse effect. The pressure and temperature variation can affect the storage stability of CO2 hydrate. In order to investigate the spatial differences in pressure and heat transfer characteristics of CO2 hydrate mixed system and the morphological evolvement process with dissociation during depressurization stage, a 100 L high-pressure reactor is used to take comprehensively experimental study. Furthermore, the effects of environmental heat flux and hydrate volume fraction on dissociation behavior and hydrate stability are also analyzed. The results indicate that the energy of hydrate mixed system is spatially inhomogeneous during dissociation and the heat flux flows to the region where the sensible heat is greatly consumed. And the bottom temperature is approximately 1.4-fold versus upper temperature. The depressurization dissociation process can be divided into dissociation stable stage (DSS) and dissociation weakening stage (DWS). The duration of DSS at depressurization stage of 1.5–1.2 MPa is around 3-fold versus stage of 2.5–2.0 MPa. •A 100 L high-pressure reactor was used to study the CO2 hydrate dissociation.•Spatial differences of pressure and temperature were specially investigated.•Dissociation by step-wise depressurization and thermal stimulation was studied.•Inhomogeneity of energy distribution in the spatial difference was explored.