OLI Studio Frequently Asked Questions - FAQ

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Frequently asked questions about OLI Studio (including Stream Analyzer, Corrosion Analyzer, Scalechem and EVS)

Stream Analyzer

Are the Partial Pressures calculated in Autoclaves always at final conditions?

The autoclave calculation was designed to allow the user to specify the partial pressures of CO2, H2S and CH4. The program can then calculate the conditions necessary to achieve those partial pressures.

A common problem in a real-world autoclave is that the partial pressures are known but it is unknown how to charge the autoclave to obtain the desired conditions. Thus the autoclave calculation has ambient and final set of conditions. The ambient is how to charge the autoclave and the final is at operating conditions.

To answer the question, the partial pressures specified in the calculation are always at the conditions specified, either ambient or final conditions.


ScaleChem

Which thermodynamic framework is more accurate for ScaleChem calculations?

The answer to this is "Depends." Starting with version 9.6.1 we developed the MSE-SRK thermodynamic framework. This was specifically developed for light hydrocarbons at high pressure. The link to MSE-SRK explains in great detail why this framework was developed.

For most ScaleChem type of calculations OLI recommends MSE-SRK. Remember it is only available in versions 9.6.1 or later.

The option to use the MSE vs AQ thermodynamic frameworks depends on several factors. If you have legacy calculations that date back to the ScaleChem - Standard program (which only supported the AQ thermodynamic framework) then you should probably stay with that framework. Otherwise OLI recommends MSE-SRK over just MSE. Of course there are components in MSE that are not in MSE-SRK (such as heavier organic acids) which would mean that you should use MSE instead but these are not typical ScaleChem components.


Halite (NaCl) solubility as a function of pressure

It is has been reported that the solubility of halite (NaCl - sodium chloride) has some pressure dependence. Some users have reported a maximum in solubility being reached near 500 bar and then the solubility decreasing. OLI has found data to much high pressures and has the following plot.

2019-07-23 10-41-19.jpg


The maximum that is predicted is about 2000 atmosphere with the data being predicted slightly higher. This is at 25 oC

What units can I use for brine entry?

The input units for brine entry are purposely limited to only a select few.

From the brine entry dialog:

2019-07-23 13-59-49.jpg

Select the Units drop-down box:

2019-07-23 14-02-30.jpg

You can select from these units. The most common are mg/L and ppm(mass). Sometimes mole % is used as in the following example:

2019-07-23 14-05-14.jpg