Accelerated Hydrate Crystal Growth in the Presence of Low Dosage Additives Known as Kinetic Hydrate Inhibitors

Abstract

Kinetic hydrate inhibitors (KHIs) or low dosage hydrate inhibitors (LDHIs) are known as additives employed to delay the onset of gas hydrate nucleation time in hydrocarbon pipelines. It has been observed, however, that in laboratory experiments accelerated hydrate growth called catastrophic growth can occur. This may be a serious problem if it occurs in a field application of kinetic inhibitors. The mechanism of such accelerated hydrate growth in the presence of KHIs is still not understood. A high-pressure microdifferential scanning calorimeter was employed to study the accelerated hydrate growth in the presence of chemical and biological inhibitors. It is hypothesized that capillary action facilitates the transport of water molecules across the formed hydrate layer from the bulk of the liquid water phase to the gas–liquid interface. This in turn might be the governing mechanism for catastrophic hydrate growth in the presence of KHIs. In addition, the hydrate catastrophic index is introduced in this work as a parameter to quantify the phenomenon based on the laboratory data and the type of experiment conducted. The HCI may then serve as a measure of the pipeline hydrate plugging potential.