Energy & Fuels, Vol.31, No.8, 8505-8511, 2017
Effect of Poly Vinyl Caprolactam Concentration on the Dissociation Temperature for Methane Hydrates
The use of KHI in conventional gas production has become common, but its applicability to methane hydrate production has not yet been extensively studied) particularly in the presence of residual hydrate structures. Methane gas from marine hydrate deposits can be produced by methods like depressurization, thermal stimulation, and the injection of hydrate inhibitors. Because residual hydrate structures known as hydrate precursors will exist in the liquid water phase after dissociation, the risk of methane hydrate reformation has to be evaluated during the production and transportation of methane gas through offshore pipelines. Even though one viable option to avoid hydrate reformation is injecting hydrate inhibitor before transporting the fluids through pipelines, one must consider the effect that these chemicals have on hydrate plug dissociation. In the research literature, results regarding dissociation phenomena are few. This study reports the effect on dissociation for methane hydrates formed with the kinetic hydrate inhibitor Poly Vinyl Caprolactam. (PVCap). Kinetic inhibitor concentrations ranging from 40 to 6000 ppm have been,examined. Results reveal that PVCap concentrations of 750 and 1500 ppm result in nearly equal displacement of the dissociation temperature, compared to noninhibited hydrates. Furthermore, 3000 and 6000 ppm PVCap give an identical increase in the dissociation temperature. Even PVCap concentrations as low as 40 ppm produce a higher dissociation temperature than corresponding hydrates, formed without an inhibitor. Thus, more energy is, required to remove hydrates formed under conditions where the kinetic inhibitor PVCap is applied. This is a factor that must be considered in the field of flow assurance.