Gas hydrate and cold seep systems, closely related to focused fluid flow derived from the deep sag or basin, are prevalent in both active and passive continental margins. Fluid flow is a key controlling factor in the formation and development of gas hydrate and cold seep systems. However, most studies focus mainly on the seafloor or shallow subsurface, while there are relatively few shallow-deep coupling studies on the potential relationship between the seabed processes of cold seep activities and the deep strata in the basin.

At the same time, heat and mass transfer occurs during fluid migration and accumulation, accompanied by cold seep activity and the dynamic changes of natural gas hydrates. Research in this area is of great significance for the further understanding of the fluid activities and natural gas hydrate exploration under the extreme conditions of the deep-sea environment with low temperature and high pressure. Therefore, there is a significant need to explore the relationship between seafloor cold seep systems and fluid activity originating from the deep strata of the basin, the process of mass and heat transfer that occurs during the migration of deep gas-bearing fluids to the seabed, and the characterisation of the impact of fluid activity on shallow seafloor natural gas hydrates.

The aim of this Special Issue is to focus on new discoveries and new methods, comprehensive laboratory experiments and field investigations, theoretical and numerical simulation, and in-depth understanding of the coupling relationship between cold seeps and natural gas hydrate systems and fluid activities in depth. The kinetic mechanisms of migration and transfer of heat, gas-bearing fluids, pore water substances, and its effect on natural gas hydrate accumulation are all areas of interest. We welcome both original research and review articles.

Potential topics include but are not limited to the following:

• Geophysical characterisation of focused fluid flow pathways and their sources
• New technology of submarine observation and testing of cold seeps and associated gas hydrates
• Sedimentation and structure control on the development of fluid flow
• Pressure regimes controlling fluid migration
• Spatial and temporal variation of fluid flow
• Long-term monitoring of fluid migration
• Authigenic mineral precipitation and gas hydrate formation during fluid flow
• Hydrate-bound gas and its origin
• Geothermal influence on gas hydrate stability
• Numerical modelling of gas-bearing fluid