Effect of N-methyl-diethanolamine and film forming corrosion inhibitor on gas hydrate, and empirical modeling for degradation

Abstract

Chemical inhibition is a common solution to hydrate formation in gas pipelines. Monoethylene glycol (MEG) and kinetic hydrate inhibitor (KHI) are the most commonly used hydrate inhibitors, whilst N-methyl-diethanolamine (MDEA) and film forming corrosion inhibitor (FFCI) are usually used as part of a corrosion control program to go alongside these hydrate inhibitors. In this study, the methane hydrate inhibition performance of MDEA and FFCI in the presence and absence of a hydrate inhibitor were assessed. The study found that both MDEA and FFCI may improve the overall hydrate inhibitory performance of the combined solution. When combined with KHI an increase in induction times was found. FFCI may act as a thermodynamic hydrate inhibitor, and thus enhance the hydrate inhibitory performance alongside MEG. Furthermore, two empirical models were developed to cater for MEG and MDEA + MEG degradation effect on hydrate phase equilibrium temperature, as this effect cannot be simulated in flow assurance prediction software. Moreover, these models and previously developed models were combined wholesomely in the form of an algorithm to determine the hydrate phase equilibrium temperature.