Hydrates can form at pressures and temperatures found in natural gas and oil pipelines, causing blockages, especially when temperatures fall significantly such as when closing in a well or flowing gas through a choke. Several mitigation techniques and subsea architectures can be applied in order to avoid or to minimize the risk of forming hydrates.
The most common technique today, during production and shutdown is the use of Thermodynamic Inhibitors (MEOH, MEG, DEG and TEG). The thermodynamic inhibitors hinder the hydrate formation by lowering the freezing point of a stream. Recently, the use of Low Dosage Hydrate Inhibitors (kinetic inhibitors and antiagglomerants) is considered as also an option. The required concentration of these inhibitors is very low (0.5–2% wt). Their performance is quite good, but very toxic due to high concentrations of amins (1). Owing to their low dosage, the most interesting economic advantage expecting from LDHIs should have been the reduction of OPEX, but their high price lead to same OPEX as THIs. Moreover, field architectures, which provide the possibility of dead oil recirculation and pipelines' depressurization before scheduled shutdowns and for hydrate plug removal respectively, are very common approaches and used very often.
