The impact of mono-ethylene glycol and kinetic inhibitors on methane hydrate formation

Rigorous quantification of hydrate formation probability in the presence of mono-ethylene glycol (MEG) is crucial for understanding hydrate formation risk in oil and gas production systems where the delivery of MEG for complete thermodynamic inhibition is either economically or practically infeasible. Using thermoelectrically cooled, stirred reactors, we have obtained 3,056 hydrate nucleation points in total. With these data we quantify the probability of hydrate formation in under-dosed MEG systems as a function of subcooling from the hydrate phase boundary, at MEG dosages between (5 and 25) wt% with respect to the aqueous phase. Although the addition of the MEG led to reductions in the measured formation temperatures, the corresponding subcooling distributions were similar to those measured in MEG-free systems. Furthermore, isothermal measurements at a fixed subcooling of (3.6 +/- 0.1) K across a range of MEG loadings yielded comparable exponential induction time distributions. These results establish that MEG does not significantly affect either the nucleation rate or distribution of hydrate formation probabilities. Initial subcooling-dependent hydrate growth rates were also measured and reduced proportionally with the MEG dosage. Finally, we show how a low dosage kinetic hydrate inhibitor can be used together with MEG to further inhibit hydrate formation, by reducing both nucleation and growth rate. The results detailed here may be useful to the successful implementation of economically-viable, risk-based hydrate management strategies in under-inhibited systems.