Frequently Asked Questions (FAQ) about MSE-SRK

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MSE-SRK is a relatively new thermodynamic model in the OLI Software. Here are some frequently asked questions about the model.

Contents

MSE-SRK Development

Why was MSE-SRK developed?

MSE-SRK was developed to overcome a weakness in MSE: prediction of phase equilibrium of mixtures containing hydrocarbons and/or light gases (CO2, H2S, N2), with or without H2O, over a wide range of temperatures and pressures, including the near-critical region. MSE-SRK is generally intended for gas and oil production and autoclaves. It may also be useful for refinery and petrochemical applications that involve only hydrocarbons.


Which equations of state are used with MSE-SRK?

The Equation of State depends are which phase you are considering:

Method Aqueous MSE-SRK MSE
Vapor Phase Model SRK SRK SRK
2nd Liquid Phase Model SRK SRK MSE
Aqueous Phase Model Bromley MSE MSE


MSESRK can be considered as a “halfway” implementation of MSE relative to the Aqueous method. That is MSE only replaces Bromley for the aqueous phase model. This captures most of the benefits of MSE since it is a much superior aqueous phase model then Bromley. The other 2 models are the same as Aqueous. The MSE method is the full implementation of MSE since it is also used for the 2nd liquid phase.

Guidelines for choosing between MSE and MSE-SRK

MSESRK can be considered as a “halfway” implementation of MSE relative to the Aqueous method. That is MSE only replaces Bromley for the aqueous phase model. This captures most of the benefits of MSE since it is a much superior aqueous phase model then Bromley. The other 2 models are the same as Aqueous. The MSE method is the full implementation of MSE since it is also used for the 2nd liquid phase.


Is there a 2nd liquid phase (non-aqueous)?

If NO then use MSE IF YES then see the next question

does the 2nd liquid phase consist mostly of hydrocarbons and/or light gases?

If NO then use MSE If YES then use MSE-SRK


Therefore, MSESRK should only be used when there is a 2nd liquid phase, and that phase contains mostly hydrocarbons and/or light gases.

MSESRK versus MSE when there is no 2nd liquid phase.

MSESRK is intended to be the same as MSE when there is no 2nd liquid phase. If the 2nd liquid phase is turned off, then the software will define the liquid phase as an aqueous phase, and it will be the same as MSE. However, if the 2nd liquid phase is turned on and there is only 1 liquid phase, the properties will depend on whether the software defines that liquid as a 2nd liquid phase or an aqueous phase. The properties will be calculated by MSE if it is defined as an aqueous phase but will be calculated by SRK if it is defined as a 2nd liquid phase. The phase definition generally depends on the amount of water in the phase. MSESRK works best and is intended for situations when there are 2 liquid (hydrocarbon/light gas and water) phases.

SRKMSE Databank

SRKMSE is implemented in the software as a “special” private databank where MSEPUB is the primary databank. It is treated as a normal private databank in that the data in SRKMSE overrides the corresponding data in MSEPUB. It is “special” because when it is selected the model for calculating the 2nd liquid phase properties is changed from MSE to SRK in the software. Since MSEPUB is still the primary databank, all the ions, aqueous species (without a vapor phase species) and solid species that it contains are also available in MSESRK. However, while predictions can be made with vapor species, they may not be reliable for vapor species that are not hydrocarbon, light gas or water (exceptions below).


MSESRK minor components

MSESRK can reliably predict the amount of dissolved H2O in hydrocarbons and light gases. Several other components were also included in the MSESRK databank: MEG, DEG, TEG, formic acid, acetic acid, methanol, mercury and sulfur(V11) so that reliable predictions can be made when there is a small amount of these components dissolved in hydrocarbons or light gases. This was done by developing SRK interaction parameters for these components in hydrocarbon mixtures. However, these parameters will only give reliable predictions when there is a small amount (less than about 10%) of them in the hydrocarbon mixture. This should be sufficient for the gas and oil production applications that MSESRK is intended for.