Gas Hydrates

The term gas hydrates refers to nonstoichiometric species belonging to the group of clathrates. They should be distinguished from the stoichiometric hydrates common to inorganic chemistry, for example, CaCl2.6H2O (antarcticite). Gas hydrates, or clathrate hydrates, are a group of ice-like, crystalline inclusion compounds, which form through the combination of water and suitably sized molecules, typically under low temperature and elevated pressure conditions. The petroleum industry is facing a flow assurance challenge with hydrate deposits in subsea pipelines where hydrate often forms at inaccessible locations. Hydrate formation could be a serious threat to the safe and economical operation of production/transportation facilities. One of the problems, other than blockage, is the movement of the hydrate plugs in the pipeline at high velocity, which can cause rupture in the pipeline and therefore create a severe safety and environmental hazard. Therefore an understanding of how, when, and where hydrates form is necessary to overcome hydrate problems. These questions have become all the more crucial since deepwater fields have been discovered or brought into production, where these fields are perfect candidates to encounter hydrate-forming conditions. This chapter answers these crucial questions and provides significant information on the best method to prevent and remediate hydrates in hydrocarbon production and transportation systems.