Critical Conditions for CO2 Hydrate Films To Rest on Submarine CO2 Pond Surfaces: A Mechanistic Study

Abstract

The stability of hydrate films formed at the horizontal interface between seawater and denser liquid CO2 under high pressures (≳35 MPa) is considered to have an insight into the feasibility of the disposal/storage of liquid CO2 in the deep oceans. Hydrate films formed at the interface (i.e., the surface of a liquid CO2 pond on the seabed) may be denser than both liquid CO2 and seawater, may be denser than seawater but lighter than liquid CO2, or may be lighter than both liquids depending on the ambient pressure (i.e., the depth of the interface) and also on the fractional occupancy of hydrate crystalline cavities by CO2 molecules. The static force balance between the gravitational forces and the interfacial tension force acting on each hydrate film is formulated, thereby predicting the critical condition beyond which the film may sink into the CO2 pond or buoy up into the sea, or it may be broken due to an internal stress.