The Effect of Salt-Laden Degraded MEG on Gas Hydrate Inhibition

Abstract The formation of gas hydrates in pipelines continues to be a major challenge in gas production. Conventionally, thermodynamic hydrate inhibitors (THIs) are used to inhibit hydrate formation. Mono- ethylene glycol (MEG) is commonly utilized as a hydrate inhibitor due to its recoverability. However, during the recovery process, MEG may undergo multiple phases of thermal exposure which may lead to the degradation of MEG. In this study, MEG solution with realistic brine composition was tested for its gas hydrate inhibition performance. The typical lean-MEG solution was prepared by combining pure MEG in a brine solution based on common formation water salt composition. The degraded samples were extracted from a MEG recovery pilot plant that had undergone a complete recovery operation (~13 h). Samples were then taken for gas hydrate testing using a high-pressure PVT cell. The isobaric hydrate testing method was employed for accurate hydrate equilibria results. The new hydrate equilibria data revealed a hydrate promotion effect amongst the degraded MEG samples as opposed to pure non-degraded MEG. Although salt in the MEG solution improved hydrate inhibition, the results show that the inhibition effect was decreased as the extent of MEG degradation increased. Furthermore, MEG degradation products were identified to be acetic, formic, and glycolic acid. Observations reveal a color change from colorless to slightly yellow depending on the extent of thermal degradation of the MEG samples.