Rheology Properties of Cyclopentane Hydrate Slurry in the Presence of Wax Crystals

ABSTRACT

There are several flow assurance problems for the energy development in deep-water, the coexistence of wax and hydrate resulting to multi-solid phase deposition is among the most difficult to overcome. The results of an experimental study on the effect of wax content, water cut, subcooling and static time on the CP hydrate-forming mixtures are reported. The droplet distribution at different wax contents is determined by using microscopic observation method. Using dynamic stress measurements method, a correlation between rheological properties and water cut is obtained. Hydrate nucleation, growth, dissociation, and slurry rheological properties, including critical time, growth time, final viscosity, and yield properties are determined. Results indicated that wax inhibit hydrate nucleation and growth, but the viscosity of hydrate slurry in waxy system is still higher than wax-free system due to the wax-hydrate aggregates contribute more to the viscosity of the system. The structure of hydrate slurry containing wax system is more stable and more difficult to be damaged by shear. Wax increases the hydrate slurry yield stress, and this effect is more significant at higher water cut and longer static times. The yield stress of the hydrate slurry was linearly related to the water cut. 35% was the critical water cut. Below the critical water cut, the slurry had better flow ability and less yield stress. Above the critical water cut, the yield stress increased significantly with water cut. The yield stress increased with increasing static time and decreases with increasing temperature. Nevertheless, the coupling effect of temperature with water cut and wax content was complex. Below 3 wt% wax content, temperature only has a significant effect on the yield stress of slurries with 40% and 50% water cut. Above 3 wt% wax content, temperature has a significant effect on the yield stress of all slurries with a 20–50% water cut. No ice formation in the CP hydrate-forming mixtures at −4°C, and the dissociation temperature of the hydrate decreases as the concentration of CP in the oil phase decreases.

KEYWORDS:

• Hydrate
• Slurry viscosity
• Wax-hydrate aggregates
• Yield stress
• Nucleation

Acknowledgements

This work is funded by the National Natural Science Foundation of China (Grant No. U19B2012, 52106208) and Natural Science Foundation of Sichuan Province (Grant No. 2023NSFSC0924).

Disclosure statement

No potential conflict of interest was reported by the authors.

SUPPLEMENTARY MATERIAL

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15567036.2023.2224740

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [U19B2012; 52106208]; Natural Science Foundation of Sichuan Province [2023NSFSC0924]