Experimental Study On Hydrate Formation And Slurry Flow In Waxy Systems

The study of hydrate formation and slurry flow in waxy systems is of great significance for the hydrate risk control of oil-gas-water multiphase transmission and the security insurance of deep-water oil and gas flow.By carrying out hydrate formation and slurry rheological experiments on a high-pressure hydrate experimental loop,the hydrate formation,hydrate slurry viscosity and hydrate slurry flow resistance in waxy systems are studied in this paper.Firstly,by comparing the variation of parameters like the temperature and pressure during the process of hydrate formation in waxy systems and in wax free systems,the effects of the precipitation of wax crystals on the hydrate formation process are analyzed and for the induction time of hydrate formation,which is an important parameter characterizing the hydrate formation process,the effects of temperature,pressure,flow rate and wax content on it in waxy systems are studied.Then,the classical solid-liquid three-layer flow model is applied to the calculation of hydrate slurry viscosity and by comparing the viscosity calculation results of the hydrate slurry in waxy systems and in wax free systems,the effects of the wax crystals precipitated in waxy systems on the hydrate slurry viscosity characteristics are studied.What’s more,two viscosity prediction models of the hydrate slurry in waxy systems are established based on the rheological constitutive equation and the effective medium theory respectively,which can both quantitatively characterize the viscosity of hydrate slurry in the current experimental waxy systems well.Finally,the steady-flowing hydrate slurry in waxy systems is regarded as a pseudo-single-phase fluid and the changing rule of the slurry flow resistance during the process of hydrate slurry formation and flow in waxy systems and the influence of wax precipitation on the hydrate slurry flow resistance are analyzed.Based on the generalized Reynolds number definition of non-Newtonian fluids,a semi-empirical model for predicting the flow resistance coefficient of hydrate slurry in the current experimental waxy systems is established using the empirical model of Berahius type.