Abstract
Gas hydrate and corrosion inhibitors are widely used to ensure successful and economic hydrocarbon stream flow inside the oil and gas pipelines. However, compatibility problems are observed during their co-injection into the flowlines as they have different molecular chemistry. Modifying effective gas hydrate inhibitors, such as polyvinylcaprolactam (PVCap), with some active functional groups in corrosion inhibition, can overcome compatibility issues. In this study, maleic anhydride was used as a cheap monomer to synthesize ionic N-vinyl caprolactam/maleic-based copolymers (P(VCap-co-MA)) as potential dual-purpose gas hydrate and corrosion inhibitors. The gas hydrate experiments showed that the inhibitors effectively inhibited natural gas hydrate formation and a maximum subcooling temperature of 14.6 °C achieved in a solution containing 2500 ppm P(VCap-co-MA)-3. The molecular dynamics simulation revealed that P(VCap-co-MA)-3 reduced the gas concentration in the liquid phase and occupied its adsorption sites on the hydrate surface to form a steric hindrance effect, inhibiting the gas hydrate formation. Electrochemical measurements indicated that P(VCap-co-MA)s significantly suppressed steel corrosion in oilfield-produced water saturated with H2S and CO2. P(VCap-co-MA)-3 and P(VCap-co-MA)-5 provided the highest protection of 96.9 and 96.1% in H2S and CO2 media, respectively. Moreover, simulation studies demonstrated that the inhibitors are strongly adsorbed on the steel surface to form a barrier layer on the surface, protecting against corrosive electrolytes. These findings suggest that the modification of a gas hydrate inhibitor improves not only its corrosion and gas hydrate inhibition performance but also decreases the operation costs for flow assurance in the oil and gas pipelines.
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