DSC and thermal imaging studies of methane hydrate formation and dissociation in water emulsions in crude oils

摘要

The processes of methane hydrate formation from 50 mass% water-in-oil emulsion from the Mamontovskoe, Sovetskoe, Van-Eganskoe, and Vakhskoe oil deposits (East Siberia) were studied using differential scanning calorimetry. It was shown that different types of thermal effects may be observed in curves corresponding to the formation of hydrate (and/or ice) in different emulsions. In particular on the curves, we observed the appearance of a single asymmetric thermal effect or a set of a large number of separate small thermal effects. The analysis of the results allowed us to conclude that hydrate formation (ice freezing) in the studied emulsions occurs as a collective process, which involves a lot of water droplets in the emulsions. This process occurs in some space inside the emulsion sample. The volume of this space determines the type of curve recorded in experiment. Secondary nucleation (nucleation of the solid phase due to the contact of a drop of water with the neighboring hydrate or ice particle) enables fast formation of gas hydrate in all droplets inside this space.