Molecular simulations as a tool for selection of kinetic hydrate inhibitors

Natural gas hydrates are ice-like structures in which water molecules form a cage around gas molecules. They have been a problem in the petroleum industry. The heavy cost of alcohol and glycol injections needed to suppress the formation of hydrates has spurred an interest in so-called "kinetic inhibitors", able to slow down the hydrate formation rather than prevent it. An earlier work (Kvamme, B. et al. 1997, Mol. Phys. , 90, p. 979) proposed a simulation-based scheme to assess the comparative performance of prospective inhibitors and select the best candidates for experimental testing. In this work, we employed molecular dynamics simulations to test several kinetic inhibitors in a multiphase water-hydrate system with rigid hydrate interface. In addition, a long-scale run was implemented for a system where the hydrate was free to melt and reform. Our conclusion that PVCap inhibitor will outperform PVP as a kinetic hydrate inhibitor is supported by experimental data. We demonstrate that numerical experiments can be a valuable tool for selecting kinetic inhibitors as well as provide insight into mechanisms of kinetic inhibition and hydrate melting and reformation.