EFFECT OF UNDERINHIBITION WITH METHANOL AND ETHYLENE-GLYCOL ON THE HYDRATE-CONTROL PROCESS

Hydrate control can be achieved by chemical injection. Currently, meth anol and ethylene glycol are the most widely used inhibitors in offsho re hydrate control operations. To achieve effective hydrate inhibition , a sufficient amount of inhibitor must be injected ro shift the therm odynamic equilibrium condition for hydrate formation outside the pipel ine operating pressure and temperature. Recently published field exper iments showed that hydrate blockages form more readily in underinhibit ed systems than in systems completely without inhibitor. A laboratory study is conducted to determine the effect of low concentration (1 to 5 wt%) methanol and ethylene glycol on the hydrate formation process. The results show that, although these chemicals art: effective hydrate inhibitors when added in sufficient quantities, they actually enhance the rate of hydrate formation when added at low concentrations to the water. Furthermore, the presence of these chemicals seems to affect t he size of the forming hydrate particles.