In Situ Viscosity Measurements of a Cyclopentane Hydrate Slurry in Waxy Water-in-Oil Emulsions

With the tendency of the offshore petroleum industry moving to the deep-water fields, there are several challenges for the exploration and development of oil and gas with higher paraffin content in the deep-water severe environment, especially the complex flow assurance issues including the coexistence of wax precipitation and hydrate formation. The effects of wax on hydrate slurry viscosity, hydrate nucleation and growth, and hydrate dissociation were investigated in a rheometer. Results indicated that the stage characteristics of viscosity evolution during hydrate formation in waxy and wax-free emulsions were different, and two stages could be observed during the hydrate growth process in the presence of wax. Hydrate slurry viscosity increased with the wax content. The coupled hydrate-wax aggregates were difficult to be broken by the constant shearing force. The shear-thinning property of the hydrate slurry was not affected by the precipitated wax. Hydrate formation was inhibited due to the wax precipitated in the oil phase. Specifically, cyclopentane hydrate critical time and growth time increased with the wax content. The calculated hydrate volume fraction decreased with the wax content based on the suspension viscosity model. It was difficult for a water bridge to form between two hydrate particles during the hydrate-dissociation process with 3.0 and 5.0 wt % wax contents; therefore, no obvious increase in the slurry viscosity was observed when the slurry viscosity decreased during the dissociation process.