A Rheological Study of Parameters That Influence the Formation of Cyclopentane Hydrates

Abstract

In the oil industry, gas hydrates formed during oil and gas production are one of the main issues in flow assurance. In extreme conditions of high pressure and low temperature found in ultradeep oil wells, hydrates crystals can form, agglomerate, and accumulate in the flowlines. Moreover, hydrates can be used for energy storage and chemical separation, such as seawater desalination. As such, understanding the onset of hydrate formation, its growth, and its behavior under shear are of great interest. This work presents a rheological analysis of cyclopentane hydrates formed in water-in-oil emulsions. We present the rheological behavior from hydrate formation until a quasi steady-state regime is obtained and analyze the influence of some important parameters such as pretreatment temperatures, cooling/heating rates, and final temperature of cyclopentane hydrate formation. Other parameters explored are shear rate and water cut. The rheological behavior is obtained using a rotational rheometer at temperatures above the water freezing point to avoid the influence caused by the presence of ice. Transient tests are performed to obtain the hydrate induction and growth times. Steady state and oscillatory tests are obtained to evaluate the resulting hydrate slurry rheology. It is observed that the slurries show elasticity and a shear thinning behavior, caused likely by both mechanisms, the breakdown of the hydrate structures, and the alignment of hydrate agglomerates to the flow.