Flow characteristics of methane hydrate slurry in the transition region in a high-pressure flow loop

Abstract

The flow characteristics of methane hydrate slurry formed from an 100% water cut system at a flow rate (mean velocity) range from 0.62 to 3.84 m/s were experimentally investigated in a high-pressure flow loop. The effects of hydrate volume fraction, tube diameter and flow rate on the flow regimes, pressure drops and the coefficients of pipe friction were measured. The experimental results indicated that a turbulent flow took place easily at low hydrate volume fraction region with a relatively high flow rate, while it transformed into a laminar flow with the increase of the hydrate volume fraction. There existed a critical value of hydrate volume fraction where the transition occurred. In the turbulent flow regime, the coefficients of pipe friction were close to that of the continuous phase (water in this study) and the effects of hydrate volume fraction and flow rate could be neglected. In the laminar flow regime, methane hydrate slurry could be considered as a pseudoplastic fluid and presented shear-thinning behavior which got more obvious with the increase of the hydrate volume fraction. An empirical Herschel-Bulkley-type equation was established based on the experimental data and the flow characteristics of methane hydrate slurry could be estimated in pipes with different diameters based on the modified hydrate volume fraction. It was of great significance for hydrate slurry transportation not exceeding the critical value of hydrate volume fraction.