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Gas hydrate formation probability distributions: The effect of shear and comparisons with Nucleation Theory
Journal article   Peer reviewed

Gas hydrate formation probability distributions: The effect of shear and comparisons with Nucleation Theory

E.F. May, V.W. Lim, P.J. Metaxas, J. Du, P.L. Stanwix, D. Rowland, M.L. Johns, G. Haandrikman, D. Crosby and Z.M. Aman
Langmuir, Vol.34(10), pp.3186-3196
2018
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Abstract

Gas hydrate formation is a stochastic phenomenon of considerable significance for any risk-based approach to flow assurance in the oil and gas industry. In principle, well-established results from nucleation theory offer the prospect of predictive models for hydrate formation probability in industrial production systems. In practice, however, heuristics are relied on when estimating formation risk for a given flowline subcooling or when quantifying kinetic hydrate inhibitor (KHI) performance. Here, we present statistically significant measurements of formation probability distributions for natural gas hydrate systems under shear, which are quantitatively compared with theoretical predictions. Distributions with over 100 points were generated using low-mass, Peltier-cooled pressure cells, cycled in temperature between 40 and −5 °C at up to 2 K·min–1 and analyzed with robust algorithms that automatically identify hydrate formation and initial growth rates from dynamic pressure data. The application of shear had a significant influence on the measured distributions: at 700 rpm mass-transfer limitations were minimal, as demonstrated by the kinetic growth rates observed. The formation probability distributions measured at this shear rate had mean subcoolings consistent with theoretical predictions and steel–hydrate–water contact angles of 14–26°. However, the experimental distributions were substantially wider than predicted, suggesting that phenomena acting on macroscopic length scales are responsible for much of the observed stochastic formation. Performance tests of a KHI provided new insights into how such chemicals can reduce the risk of hydrate blockage in flowlines. Our data demonstrate that the KHI not only reduces the probability of formation (by both shifting and sharpening the distribution) but also reduces hydrate growth rates by a factor of 2.

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Collaboration types
Industry collaboration
Domestic collaboration
International collaboration
Citation topics
8 Earth Sciences
8.312 Gas Hydrates
8.312.1202 Gas Hydrate
Web Of Science research areas
Chemistry, Multidisciplinary
Chemistry, Physical
Materials Science, Multidisciplinary
ESI research areas
Chemistry
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