Kinetic of Hydrates Formation: Influence of Crude Oils

Abstract As deepwater offshore production is widely developing, the problem of flow assurance becomes of major importance. Among the problems that can be encountered, flow lines plugging by hydrates is particularly dread. The kinetic of hydrate's formation is greatly influenced by the nature of the crude oil produced and the management of hydrate's problems could be quite different from one field to another. We have studied the kinetic of hydrate's formation using four different liquid hydrocarbon phases: a condensate, a paraffinic and two asphaltenic crude oils. The kinetic of hydrate's formation has been studied in a semi-batch stirred reactor. Experiments have been carried out in presence of these liquid hydrocarbon phases, at a constant pressure by decreasing temperature. The induction time, the quantity of hydrates formed and their rate of formation have been determined at different water cuts. Two types of kinetic behavior have been found: the condensate and the paraffinic crude show very violent and rapid hydrate's formation, while hydrate's formation with the asphaltenic oils is delayed and the crystallization is very smooth. The influence of the liquid hydrocarbon's composition (paraffin content, WAT, asphaltene's solubility…) has been explored. The effects of the water cut and of liquid hydrocarbon's viscosity have been also studied. Among these, the most relevant parameters having an important effect on the kinetic of hydrate's formation have been pointed out. This work highlighted the importance of the nature of the liquid hydrocarbon phase on the kinetic of hydrate's formation. Specific studies on the influence of the hydrocarbon phase can give precious information for hydrate's management problems in deepwater offshore development.