Thermodynamic Properties of Reservoir Fluids

The thermodynamic properties such as density, enthalpy and viscosity of the reservoir fluid phases can be computed in different ways:

• by the mean of analytical models

• by external databases given in the format accepted by Cirrus

• by PVT table formats commonly used in reservoir engineering

The input keyword to enter the properties of a phase is EOS, which stands for Equation of State, followed by the name of the phase.

Water properties are required for all flow models.

Gas properties are required for Gas-Water, Multi-Gas, Black Oil, Todd-Longstaff and Solvent models.

Oil properties are required for Oil-Water, Black Oil, Todd-Longstaff and Solvent models.

The properties of the solvent component are required for the Multi-Gas and Solvent models. For Todd- Longstaff, the gas properties define the solvent properties, as the gas is effectively the solvent for this model.

The multi-component modelling option uses a multi-component equation of state (EOS COMP) that can be used to define only the non-aqueous phases when the Peng-Robinson (PREOS) or Soave-Redlich-Kwong (SRKEOS) EoS is used. With the Søreide-Whitson EoS (SWEOS) added in 1.9, Cirrus offers the option to characterise all three phases with the same EoS.

The following EOS cards are available:

• EOS WATER
• EOS OIL
• EOS GAS
• EOS SOLVENT
• EOS COMP

See also the following information about databases:

• Database for real CO₂
• EOS properties database