Comparative Study of Efficiency of Hydrate Inhibitors Based on Ammonium Salts and Polyvinylpyrrolidone

This study experimentally investigated the inhibitory effects of ammonium chloride (NH₄Cl), polyvinylpyrrolidone (PVP), NH₄Cl + PVP, ammonium thiocyanate (NH₄SCN), and ammonium carbonate ((NH₄)₂CO₃) on methane hydrate formation. Phase equilibrium curves of hydrates were constructed in the presence of different salts to evaluate their performance as thermodynamic inhibitors. Experimental results confirmed that, among kill fluids with a density of 1.05 g/cm³, ammonium chloride more effectively shifts the hydrate equilibrium point compared to ammonium thiocyanate and ammonium carbonate. The inhibitor NH₄Cl + PVP (1 wt.% PVP) was shown to have no impact on the inhibitory effect of ammonium chloride at pressures below 5.5 MPa. However, at pressures exceeding 5.5 MPa, it enhanced inhibition: for example, the hydrate decomposition temperature decreased by 1.5 °C at 32 MPa. An investigation into the kinetic properties of the NH₄Cl + PVP inhibitor revealed preliminary data indicating a longer induction time for the combined inhibitor compared to NH₄Cl alone.