Inhibition Effect Study of Carboxyl-Terminated Polyvinyl Caprolactam on Methane Hydrate Formation

Injecting kinetic hydrate inhibitors (KHIs) is an efficient option to prevent gas hydrate blockages in equipment and pipelines, which widely exist in petroleum production and transportation operations. Polyvinyl caprolactam(PVCap) is a kind of effective and commercialized KHIs. In this paper, one kind of carboxyl-acid-group-modified PVCap named carboxyl terminated polyvinyl caprolactam (PVCSCOOH) has been synthesized and the KHI performance has also been evaluated. The microscopic properties for hydrate samples were detected with cryo-scanning electron microscopy, Raman spectroscopy, and powder X-ray diffraction. It was found that the maximum subcooling degree of 2 wt % PVCSCOOH not generating methane hydrate was 13.7 degrees C, while this value for PVCap was only 11.3 degrees C; PVCSCOOH had a better inhibition performance than PVCap of similar molecular weight. In addition, we also noticed that PVCSCOOH could change the hydrate appearance and lower the large/small cavity ratio (L/S), to 2.00 but it had no impact on the hydrate structure.