Objective
OLI Studio: ScaleChem
OLI Studio: Stream Analyzer
Conclusion
Objective
Solid concentrations are frequently represented as a mass per unit volume (e.g., mg/L). A common point of confusion arises because the "Volume" refers to the associated liquid phase, not the solid phase. This practice is prevalent in upstream oil and gas calculations and is also encountered in water treatment processes.
In this document, we will demonstrate examples using both OLI Studio: ScaleChem and OLI Studio: Stream Analyzer.
OLI Studio: ScaleChem
The example file for this section is provided at the end of this article.
In a basic scaling scenario, a brine has produced some solids. Below is the scaling report from OLI Studio: ScaleChem for the first point in the scaling scenario:
The concentration of BaSO₄ (Barite) is approximately 3.3 mg/L. What does this indicate? To understand this, we need to delve deeper into the OLI Studio: ScaleChem calculation results. Notice the small "+" sign next to the scaling scenario in the navigation tree:
Please click to expand it.
This particular scaling scenario includes several points. The first point (Brine Scale Scenario_Reservoir) corresponds to the report displayed above. Clicking on this object will reveal information that OLI Studio: Stream Analyzer would observe.
We have selected the report tab and scrolled down to the Species Output table. Here, BaSO₄ (Barite) shows a solid concentration of 3.3 mg/L, as reported initially. Next, we will adjust the units to represent just the mass for the solid phase:
This value is significantly different from the original 3.3 mg/L, now showing as 32,150 mg. This is the total mass of BaSO₄ produced at this point. Let’s examine the overall volumes for this calculation:
The solid volume is 1.11 L. If we take the reported mass of BaSO₄ in the solid phase and divide it by the solid phase volume, we get 32,150 mg / 1.1113 L = 28,930.3 mg/L.
This is not the 3.3 mg/L reported in the OLI Studio: ScaleChem report.
In OLI Studio: ScaleChem, the solids concentration report uses the brine liquid as the reference volume. The liquid volume in the above report is 9733.15 L.
Now, if we divide the solid mass of 32,150 mg by the liquid volume, we get 32,150 mg / 9733.15 L = 3.303 mg/L, which matches the value reported in the OLI Studio: ScaleChem report.
OLI Studio: Stream Analyzer
A worked example file is provided at the end of this article.
In this example, we will start with a simple input of H₂O and BaSO₄ and perform an isothermal calculation:
Next, we navigate to the Report tab and scroll down to the phase properties.
Continuing to scroll down, we will find the total species concentrations:
The default units have been modified to mass for the solid phase. Following the same logic as in OLI Studio: ScaleChem, we can manually calculate the solid concentration using the formula:
230.7 mg / 1.00295 L = 230.057 mg/L
We can also adjust our units for the solid to be concentration-based:
This demonstrates that the concentration of the solid phase is relative to the liquid phase, as it is in OLI Studio: ScaleChem. The slight difference between our hand-calculated value and the exact answer is due to the higher internal precision of the software.
Conclusion
Both OLI Studio: ScaleChem and OLI Studio: Stream Analyzer utilize the associated liquid phase for volume when reporting concentration units for solids.