On modelling gas hydrate inhibition by salts and organic inhibitors

We present the application of a recently developed thermodynamic model to obtain better understanding of gas hydrate inhibition effects of combinations of salts (e.g., NaCl, KCl, CaCl2) and hydrate organic inhibitors (e.g., mono ethylene glycol and methanol) used for gas hydrate prevention scenarios in the gas and oil industry. In the first section of this work, the effect of salt-organic inhibitor interactions on hydrate inhibition effects has been studied. For this purpose, two possible approaches for modelling the hydrate inhibition effect of a mixture of salts and organic inhibitors have been investigated. They are: (1) considering the summation of separate effects of salt and organic inhibitors and ignoring the effect of interaction between inhibitors, and (2) considering the effect of the mixture of salt and organic inhibitor and taking into account the effect of interaction between these. The study shows that the hydrate formation inhibiting the effect of the approach 1 surpasses the effect calculated from approach 2, especially at high concentrations of inhibitors. That means predictive hydrate numerical models and empirical correlations should precisely take into account the interaction between electrolytes and organic inhibitors in order to accurately predict hydrate inhibition effects. second section of this work, maximum gas hydrate suppression temperature locus for systems containing salts and organic inhibitors has been investigated. The aim of this section was to obtain a guideline for efficient application of combinations of salts and organic inhibitors in order to operate in the hydrate and salt free regions. It has been concluded that high concentrations of organic inhibitors are preferred to salts as far as hydrate prevention is concerned.