The reliable evaluation of thermal diffusion factors is important to understand the composition variation of the mixture components in hydrocarbon reservoirs. A thermodynamic model of thermal diffusion factors of hydrocarbon mixtures is presented. The model is based on the statistical theory of linear transport of intermolecular forces and accounts for the explicit effects of molecular mass, energy and size parameters. The accuracy of the model is first evaluated by comparing calculated results with the available non-equilibrium molecular dynamics simulation results. The theoretical model is then applied to explain thermal diffusion factors in some selected binary hydrocarbon mixtures over a range of temperature, pressure and molecular composition conditions.
Part of the book: Exploitation of Unconventional Oil and Gas Resources
The prevention of solids formation and their deposition are major challenges to design and operate any subsea hydrocarbon production systems. One of the most challenging issues is the management of paraffin/wax. As the water depth increases, at the low temperatures of subsea conditions, hydrocarbons may precipitate as wax, which can solidify and restrict the flow. During shutdown of a subsea production system wax gel may form and solidify when a crude oil cools below its pour point causing operational problems from downhole to the processing facilities. The purpose of this chapter is to address the paraffin/wax formation and deposition issues to properly design a subsea production system consisting of pipe-in-pipe flowline and flexible riser under deepwater environment. A field specific example is presented to manage the wax formation/deposition and prevent paraffin/wax deposition risks in an effective way during the normal and the shut-in operations of the subsea production system. This study illustrates that the subsea hardware, such as water stop and equipment valves, along with the flowline, riser and jumper should be sufficiently insulated in order to prevent any cold spots in the production system, and achieve sufficient cooldown time for the shut-in operations.
Part of the book: Paraffin