Molecular insights into inhibition and manipulation of methane hydrate dissociation by lecithin and poly(N-vinylpyrrolidone)

Abstract

Hydrate dissociation during the drilling operations precipitates wellbore instability and gas incursion, critically impeding the safe extraction of natural gas hydrates. Various inhibitors for hydrate dissociation were widely adopted in the drilling and production, however, understanding and manipulating the dissociation of hydrates in the presence of kinetic inhibitors remains unclear. Herein, we propose a strategy to apply terahertz electric fields to manipulate the dissociation, based on the inhibition mechanisms of two common kinetic inhibitors, Lecithin and poly(N-vinylpyrrolidone) (PVP). We elaborated on these mechanisms by investigating the dissociation of methane hydrate in both pure water (PW) and seawater (SW) using molecular dynamics (MD) simulations. The dissociation process was accelerated by the rapid growth of nanobubbles and the intrusion of ions. The hydrophobic fatty chains and hydrophilic groups in lecithin directly affected the migration of methane and water molecules through adsorption and the hydrogen bond network. Interestingly, the steric hindrance effect exerted by PVP prominently impeded the migration of methane. To maintain this steric hindrance, one electric field of 30 THz was applied to the PVP/PW system, successfully manipulating the dissociation of methane hydrate. Our findings provide valuable molecular insights into the impact and manipulation of kinetic inhibitors on hydrate dissociation.