LCST-Modulated Polymers for Synergistic Hydrate Inhibition in Methane Gas Flowlines

Synergistic hydrate inhibition of kinetic and thermodynamic inhibitors is a promising strategy for preventing hydrate blockage in flowlines. Some research has been conducted on structure II natural gas hydrates; however, there have been few reports on the synergistic inhibition of structure I (sI) methane hydrates. Herein, we synthesized LCST-modulated kinetic hydrate inhibition copolymers using reversible addition-fragmentation chain-transfer polymerization and tested their performance on sI methane hydrate inhibition in the presence of a monoethylene glycol (MEG) synergist. All copolymers generally inhibited hydrate formation, while the experimental systems were thermodynamically under-inhibited by MEG. We demonstrated that the synergistic inhibition of N-isopropylacrylamide-based copolymer and MEG are effective in preventing hydrate blockage and hydrate re-formation for systems with methane-dominant flow, and methane hydrate development in subsea sediments. These inhibition polymers with narrow phase transition regions and well-controlled lower critical solution temperatures might be helpful in preventing fouling problems caused by unexpected precipitation and designing more economical processes for flow assurance.