Renewable oilfield reagents with multiple flow-assurance actions: Oleic acid – Derived compounds inhibit gas hydrate agglomeration and corrosion

Injecting anti-agglomerant hydrate inhibitors into subsea oil and gas pipelines is considered an effective method to prevent hydrate blockage during hydrocarbon transportation. It is desirable to design anti-agglomerants that are biodegradable, effective under high subcooling temperatures, and compatible with other production chemicals, in particular corrosion inhibitors. In this study, a cost-effective and solvent-free reaction is developed to synthesize novel bio-based quaternary ammonium salts (BQAs) using oleic acid as starting material. The inhibition efficiency of BQAs on methane hydrate agglomeration was evaluated using a high-pressure autoclave at a subcooling temperature of 15 °C. Moreover, a micromechanical force apparatus was employed to quantify cohesive forces among particles of cyclopentane hydrate in the presence of BQAs at 275 K and atmospheric pressure. The results showed that BQAs have the ability to prevent hydrate plugging for a duration of up to 1000 min. Furthermore, these compounds efficiently diminish cohesive forces between hydrate particles, resulting in a reduction of up to 33 %. This leads to a dispersal of hydrate particles that can be transported through pipes. To interpret the experimental results, all-atom molecular dynamics simulations were conducted. The computational results revealed strong BQAs adsorption on the methane hydrate surface, due to the carboxylate anion aligning its hydrocarbon tails parallel to the surface. Additional experiments showed that BQAs significantly lower carbon steel corrosion by 97 % and impede the diffusion of corrosive particles in water. Overall, these results suggest that BQAs derived from vegetable oils offer a practical alternative for oil-field applications, including biodegradability, affordability, anti-corrosion and anti-agglomerant properties at high subcooling temperatures. Their compatibility with other production chemicals needs to be tested.