Gas hydrates are ice-like clathrate solids that are formed from water and small hydrocarbons at elevated pressures and at lower temperatures (Figure 9.1).1-2 The temperature below which hydrates can form increases with increasing pressure and can be as high as 25-30°C (77-86°F). Typical pressure-temperature conditions for formation of gas hydrates are shown in Figure 9.1. Gas hydrates are most commonly encountered in subsea or cold climate wet gas or multiphase (oil/water/gas) pipelines, where they can block the flow of fluids, but they can also be formed during drilling, completion, and workover operations as well as in gas-processing facilities, gas injection lines, and aqueous chemical injection in gas lift lines if the pressuretemperature conditions are right. Many multiphase production lines are designed to operate without fear of hydrate formation but problems may occur if a shut-in occurs and the fluids cool, untreated, to within the hydrate-forming envelope. Further, if a subsea well is shut-in, a hydrate plug can also form below the wellhead unless the necessary precautions are taken. The prevention of gas hydrate plugging of flow lines is considered one of the main production issues to deal within deepwater field developments.3