Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications



Abstract 036
Significance of Structure-H Hydrates in Petroleum Exploration and Transportation
Østergaard, K.K., Tohidi, B., Danesh, A., Todd, A.C.
EAGE 6th Annual Research Review, Edinburgh, UK, 18 February (1998).
Recently the effect of some heavy hydrate formers on real reservoir fluids has been investigated. The findings suggested that only structure-II heavy hydrate formers promote hydrate formation in real reservoir fluids whereas the effect of the structure-H heavy hydrate formers is negligible. In this work we investigate the effect of structure-H heavy hydrate formers further and estimate the amount of a structure-H former (methylcyclohexane) needed to change the dominating hydrate structure in a natural gas from structure-II to structure-H. The results indicate that structure-H hydrate formers do not play an important role in hydrate phase boundaries of most real reservoir fluids. However, considering transportation of hydrates as a slurry using growth modifiers, structure-H may co-exist with other hydrate structures. We also address the recent reports on the formation of structure-H hydrates in a subsea environment and suggest a possible alternative explanation for the findings.