EoS models for reservoir fluids undergoing gas injection for EOR purposes must respond correctly to multiple contacts with injection gas.
Calsep develops EoS models that accurately match routine as well as EOR PVT data:
- Swelling data including critical point on saturation pressure curve
- Equilibrium Contact and Multi Contact data
- Minimum Miscibility Pressure in Slim Tube experiment
- Gas Revaporization Experiment (for gas condensates)
The EOR PVT data may include two or more injection gases. The gases can be a hydrocarbon mixture, pure CO2 or a gas rich in H2S.
Particular emphasis is on analyzing the slim tube data. A high recovery does not always mean miscibility has developed. An equally high slim tube recovery may be seen for systems developing a liquid-liquid equilibrium persisting independent of pressure.
Asphaltene precipitation must be taken into consideration. With gas injection an asphaltene phase may form from a reservoir fluid, which would never precipitate asphaltenes if produced by natural depletion. As it is not straightforward how to handle an asphaltene phase in a compositional reservoir simulator, the decision can be to have an EoS developed suppressing asphaltene formation.
The component lumping must be chosen carefully to handle the large compositional variations seen in a field with gas injection. It may be advisable not to lump components present in the injection gas in high concentration.
Calsep can export the resulting EoS model to the most commonly used compositional reservoir and well stream simulators including
- Eclipse Comp
- VIP Comp
- More EoS
- Prosper EoS