Kinetic Hydrate Inhibition by Lambda-Carrageenan and Its Synergistic Compositions with Ethylene Glycol, 4-Methyl-1-Pentanol, Polyvinylpyrrolidone, and Polyvinylcaprolactam

Forthe oil and gas industry to function smoothly, it is essentialto have a continuous flow of oil and gas in pipelines without interruptionscaused by hydrate blockages. Kinetic hydrate inhibitors (KHIs) arebecoming popular as they offer safe and effective hydrate inhibitionat low dosages (0.5-2 wt % of the water content). The currentcommercial KHIs are synthetic and poorly biodegradable, which causesdisposal concerns for environmental regulators. The lack of natural,sustainable, and biodegradable KHIs opens the scope to develop naturaland biodegradable KHI alternatives. This study investigates the useof a natural and biodegradable polysaccharide, lambda carrageenan(& lambda;-crgn), as a standalone KHI and its combinations with biodegradablesolvents mono ethylene glycol and 4-methyl-1-pentanol and commercialKHI polymers (PVP and PVCap) for improved biodegradability and performance.& lambda;-crgn is an environmentally friendly polysaccharide derivedand cultivated from red seaweeds. Two variants of & lambda;-crgn, onewith a smaller mean size and a lower viscosity (LV) and one with alarger mean size and a higher viscosity (HV), are tested for hydrateinhibition. The lower molecular size/viscosity variant, & lambda;-crgn(LV), showed similar induction times and lower hydrate growth ratescompared to PVP when used as a standalone KHI. However, the high-viscosityvariant did not perform as well as PVP. & lambda;-crgn (HV or LV), whenblended with commercial KHIs (PVP and PVCap), synergized and led toan increase in induction times by up to 63% and a decrease in thehydrate growth rates by 73% compared to when only the commercialKHIs were used at the exact total dosages. When & lambda;-crgn (HV orLV) was blended with solvents 4-methyl-1-pentanol or MEG, again asignificant synergy was observed, leading to the hydrate inhibitionperformance that was found to be at par or better than the commercialKHIs (PVP and PVCap) at the exact total dosages.