Kinetics and morphology of gas hydrate formation from MEG solution in under-inhibited systems

Abstract

Natural gas hydrate blockages pose a major risk to deepwater oil and gas development. Thermodynamic under-inhibition is a cost-effective hydrate management strategy, but the impact of mono ethylene glycol (MEG) on hydrate formation kinetics and mass transfer at the gas–water interface requires further understanding for hydrate-related flow assurance. This study investigates the kinetics and morphology of hydrate growth from MEG solutions using in situ micro X-ray CT and a macro transparent reactor. MEG concentration emerged as the primary factor influencing hydrate growth morphology. Findings revealed that MEG alters the growth morphology of gas hydrates by inhibiting the formation of a hydrate film at the gas–liquid interface and inducing flocculent hydrate growth within the solution. MEG can also induce the formation of low-saturation hydrates, with no significant self-inhibition observed at concentrations below 20 %. Over time, a dense hydrate shell tended to form on the surface of the hydrate lump, increasing the risk of blockage. Additionally, it was observed that subcooling also affects the hydrate growth morphology; higher subcooling accelerates the hydrate growth rate and increases the density of the formed hydrate. This research explored the mechanisms underlying hydrate formation in under-inhibited systems, aiming to extend the safe operational boundary for oil and gas transportation and provide theoretical support for deepwater hydrate management.