Polymer–Methanol Combines Inhibition of Gas Hydrate Formation

Abstract

A study was carried out on combined inhibition by a solution containing 0.5% polymer kinetic inhibitor (KI) + 10.0% methanol as a thermodynamic inhibitor (TI) in the formation of methane hydrate (Class I) and the hydrate of 95.66 mol. % CH₄ + 4.34 mol.% C₃H₈ (methanepropane mixture) (Class II). This combined inhibition was studied by an isothermal method and a method entailing cooling at a constant rate using a GHA350 autoclave. Methane was shown to have an adverse effect on the inhibiting properties of the polymer KI both relative to formation of methane hydrate and hydrates of C₁–C₃ hydrocarbons. The loss of inhibition by the polymer KI in the presence of methanol is expressed as the decrease in the extent of supercooling attainable in the system without adsorption of the hydrate-forming gas (1.5–2.5°C in comparison with the system without TI). The induction time is shown to depend on the extent of supercooling in the system during inhibition of formation of the Class I and Class II hydrates by the solution containing 0.5% KI + 10.0% TI.