Effect of molecular weight of polyethylene glycol (PEG), a hydrate inhibitive water-based drilling fluid additive, on the formation and dissociation kinetics of methane hydrate

Abstract

Polyethylene glycol (PEG), a water-soluble polymer, has been widely used as the most promising polymer for designing hydrate inhibitive water-based drilling fluids. Studies involving the kinetics of methane hydrate formation and dissociation in PEG aqueous solutions may help to develop effective hydrate inhibitive drilling fluids for efficient drilling operation in deep-offshore and hydrate bearing formation. In this work, formation and dissociation kinetics of methane hydrate system have been investigated in an aqueous solution of PEG (with number average molecular weight of 200 and 600 kg/kmol; referred to as PEG-200 and PEG-600, respectively). Different concentrations of PEG, such as 0.2 and 0.4 mass fractions, have been considered for the investigations. Various experiments have been carried out at an initial formation pressure of 7.5 MPa and 5.5 MPa and 263.15 K temperature. The information on the number of moles of methane consumed during hydrate formation, rate of hydrate formation, water-to-hydrate conversion, gas-to-hydrate conversion, number of moles of gas recovered during hydrate dissociation, and rate of hydrate dissociation are being provided in this study. This study provides useful information to use effective combinations of lower and higher molecular weight polymeric systems to develop effective hydrate inhibitive water-based drilling fluid systems suitable for offshore drilling and for hydrate bearing formations.