Modelling Approach
HydraFLASH uses a range of modelling approaches to calculate the phase equilibria and physical properties of reservoir fluids at specified conditions.
Different modelling approaches are typically used which include
- Standard EoS (SRK, PR and VPT)
- Cubic Plus Association EoS (CPA)
- PC-SAFT EoS
Equation of State and Mixing Rules
A combination of equations of state (EoS) and appropriately selected mixing rules provide a powerful tool capable of modelling complicated multiphase, multicomponent systems.
The SRK and PR EoS are commonly used for modelling in the oil and gas industry and are included in HydraFLASH in addition to the Peneloux density correction and different mixing rules.
HydraFLASH incorporates the Valderrama-Patel-Teja (VPT) EoS with non-density dependent mixing rules (NDD) used in modelling fluid phases. The combination has proved to be very effective for modelling systems with polar as well as non-polar components.
The CPA (Cubic Plus Association) and PC-SAFT EoS are new approaches that have a number of advantages when modelling fluid phase equilibria for systems containing components which can form hydrogen bonds (e.g. water, methanol, ethanol, MEG).
Hydrate Phase Modelling
The hydrate phase is modelled by the solid solution theory of Van der Waals and Platteeuw. The Kihara model for spherical molecules is applied in order to calculate the potential function for compounds forming the hydrate phases.
Electrolyte Solution Modelling
Electrolytes are modelled by an improved Aasberg-Petersen model. The model can be used over a wide range of temperature and salt concentrations, and is capable of handling mixed electrolyte solutions.