Method for detecting and controlling hydrate formation at every point along a pipe in which polyphasic petroleum fluids flow

摘要

The thermodynamic conditions for hydrate formation are detected by a particular regrouping of oil fluids in pseudo-components to isolate the hydrate-forming components, defining a mass fraction and a certain number of physical properties for each one. These data are applied to the modules to determine the temperature (Td) of hydrate dissociation at all points. A mechanical hydrodynamic module and an integrated compositional thermodynamic module are used to define the phase properties. Equations for the conservation of mass and movement and energy transfer in the mixture are used to group the fluids into a limited number of pseudo-components, considering that the mixture of fluids is at equilibrium at each instant, that the polyphase mixture is variable along the pipe and that the mass of each component of the mixture is defined globally by a conservation of mass equation without considering its phase. A control unit (C) compares the temperature of the fluids with the dissociation temperature and measured are applied to combat the formation of hydrides under the command of the control unit. These methods are means of heating the pipe to raise the fluid temperature above the dissociation temperature or injecting hydride inhibitors into the pipe. The pipe is heated by being enclosed with a second pipe in a tube isolated from the surroundings, with a hot fluid circulating through the second pipe.