This paper (SPE 50972) was revised for publication from paper SPE 37201, first presented at the 1996 Offshore Technology Conference held in Houston, 6-9 May. Original manuscript received for review 23 May 1996. Revised manuscript received 10 April 1998. Paper peer approved 20 April 1998.
Hydrate control can be achieved by chemical injection. Currently, methanol and ethylene glycol are the most widely used inhibitors in offshore hydrate control operations. To achieve effective hydrate inhibition, a sufficient amount of inhibitor must be injected to shift the thermodynamic equilibrium condition for hydrate formation outside the pipeline operating pressure and temperature. Recently published field experiments showed that hydrate blockages form more readily in underinhibited 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 are 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 the size of the forming hydrate particles.