Enhanced hydrate inhibitors: Powerful synergism with glycol ethers

Laboratory tests in which gas hydrates were formed at 4 degrees C and 1000 psig in a 300 mt stirred cell show that the performance of kinetic hydrate inhibitors, including VC-713, PVCL, and VCL/VP copolymers, is greatly improved by the addition of less than 1 wt % of certain glycol ethers in the water or saltwater phases. For example, the hydrate induction time with 0.5 wt % VC-713 in seawater increased from 40 min to over 1200 min with the addition of 0.75 wt % 2-butoxyethanol. The most effective glycol ethers tested had either three or four carbon atoms in the alkoxy group. Lower homologs did not seem to have an effect, and higher homologs were insoluble in saltwater. The glycol ethers did not inhibit hydrates (at these low concentrations) without the polymer present.