Clathrate ice with gas molecules trapped in the cagelike ice crystal structure. A clathrate is a solid crystalline compound similar to snow. Natural clathrates usually contain ethane or isobutane or, less often, methane or nitrogen. They are common in permafrost areas and in seabed sediments. Clathrates also form in and block gas wells and lines and foul heat exchangers when gas is cooled. They are composed of about 90% water and 10% of one of the gases methane, ethane, propane, isobutane, n-butane, carbon dioxide or hydrogen sulfide. Methane snow is a clathrate formed by water and methane.
Clathrates have a specific gravity between 0.96 and 0.98. Potassium salts can be used as a drilling-fluid additive to inhibit clathrate formation. Gas dehydration is used to depress the dew point of produced natural gas and prevent clathrate formation, Clathrates are melted from pipes by heaters, steam, or hot water or by adding methanol or ethylene glycol.