Crude natural gas is usually saturated with water downhole at warm temperatures and high pressures, some of which condenses as it is produced at the surface. A

Crude natural gas is usually saturated with water downhole at warm temperatures and high pressures, some of which condenses as it is produced at the surface. At many points in a pipeline further water removal can be essential too. Even when not liquefied like LPG, when passing through a restriction valve or orifice, there is still additional cooling due to the product acting a bit like a refigerant. The water content may be small but the quantity of cold gas passing through a narrow point which is well below 0C eventually can build up kilos of ice and block the flow until the ambient temperature rises enough to open it back up.