Integrated equation of state modelling for flow assurance

The challenges of modelling phase behaviour for flow assurance applications involve not only gas, oil and aqueous phases but also encompass a variety of solid phases including hydrates, waxes and asphaltenes. We describe an integrated approach to the modelling process that is based on an industry-standard equation of state with a number of well-established modifications. The same underlying petroleum fluid characterisation procedure is used to generate compositional models that can describe all the fluid and solid phases for flow assurance applications. The particular characteristics of aqueous phases, electrolytes, dissolved wax and asphaltenes are handled by a series of add-on models that extend the basic equation of state. Each solid phase has its own dedicated model that is based on clear physical principles.We present examples of complex phase behaviour calculations involving multiple phases including hydrates, waxes and asphaltenes and show how the different solids interact.Although a sound description of the phase behaviour is fundamental for flow assurance, modelling the fate of precipitated solids is also important. We briefly describe our wax deposition model and demonstrate how the thermodynamic model impacts on deposition calculations.