Competitive Interfacial Effects of Surfactant Chemicals on Clathrate Hydrate Particle Cohesion

摘要

In oilfield production conditions, many chemicals are present in the form of natural surfactants that occur in the oil phase as well as additives that are injected to control the properties of the liquid phases. These additives may include low dosage hydrate inhibitors, such as kinetic hydrate inhibitors or anti-agglomerants, corrosion or scale inhibitors, dispersants, emulsifiers, etc. To achieve slurry flow in subsea oil flowlines, the agglomeration of hydrate particles must be minimized so that small, dispersed hydrate particles are transportable rather than forming larger aggregates that may plug the flowline. While many compounds that are present in flowlines are knoWn to affect the cohesion force between hydrate particles, each chemical is often studied separately, where no other additives are present. This study focuses on classifying the possible interactions of different classes of chemicals from the cohesion force between hydrate particles. A micromechanical force apparatus was used to measure the changes in the cohesion force for cyclopentane hydrates when a dispersant, dodecylbenzenesulfonic acid, a kinetic hydrate inhibitor, polyvinyl caprolactam, and a quaternary ammonium salt, Arquad 2HT-75, were added to the cyclopentane phase prior to hydrate formation. The cohesion force was tested in the presence of each individual chemical as well as when combinations of the chemicals were present during the experiment. It was found that the interaction of specific chemicals could work antagonistically (dispersant + kinetic hydrate inhibitor/quaternary ammonium salt), where the cohesion force was higher than expected for the chemical mixture than for the separate chemicals, or synergistically (kinetic hydrate inhibitor + quaternary ammonium salt), where the cohesion-reducing effect is greater than either additive produced on its own. These measurements represent an initial foray into an important but poorly understood facet of hydrate management strategies.