Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications

Abstract 112
Is Subcooling the Right Driving Force for Testing Low Dosage Hydrate Inhibitors?
Arjmandi, M, Tohidi, B., Danesh, A., and Todd, A.C.
Chemical Engineering Science, 60, 1313-1321 (2005).
The degree of subcooling is usually used as driving force for hydrate formation, however it does not encompass the effect of pressure. A comprehensive driving force for hydrate formation is a function of pressure, temperature, and concentration however its calculation is not as simple as that of subcooling. In this work, by application of two latest driving force expressions for hydrate formation, the relationship between subcooling and the true driving force at different conditions for pure gas-water and natural gas-water systems are analysed. The effect of pressure on the induction time in the presence and absence of a kinetic inhibitor have been tested at similar degree of subcooling. The results show that for pure gas-water systems subcooling is proportional to driving force with a good approximation over a wide pressure range at isothermal conditions. However for multi-component systems (e.g., natural gases), the driving force is more than that suggested by subcooling at some pressures. Changes of driving force with pressure at constant degree of subcooling for the above systems have been presented. The results show that the pressure has no significant effect on the driving force (at constant degree of subcooling) above a certain pressure range. The experimental results show that in natural gas-water system at constant degree of subcooling the induction time is not affected by pressure, however in the presence of the kinetic inhibitor tested in this study high pressure conditions decreased the induction time.

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