Synthesis and Investigation of Polymers of 2-Methacrylamido-caprolactam as Kinetic Hydrate Inhibitors

Poly(N-vinylcaprolactam) (PVCap) and related copolymers have been used as kinetic hydrate inhibitors (KHIs) for over 25 years to combat gas hydrate formation in oil and gas field production flow lines. The caprolactam groups in this polymer class have been shown previously to have a particularly strong interaction with hydrate surfaces, inhibiting crystal growth but probably also gas hydrate nucleation. We report here a study on an alternate class of copolymers with pendant caprolactam groups from the 2-methacrylamido-caprolactam (2-MACap) monomer. KHI experiments were carried out in high pressure steel rocking cells using a structure-II-forming natural gas mixture. The KHI performance of some of these copolymers exceeded that of PVCap of similar molecular weight, with further performance enhancement provided by solvent synergists.