Original synthetic study
Equilibrium wax onset is not a wax deposition forecast
Equilibrium wax appearance identifies when a solid phase becomes thermodynamically favorable in a selected model. Deposition additionally depends on transport, wall conditions, kinetics and removal.
By PetroCalcHub Team · Updated October 24, 2026 · Free to read and use
Identify the equilibrium calculation
The supported nonideal multisolid workflow uses a specified hydrocarbon mixture and documented solid–liquid equilibrium assumptions. Its onset and solid fractions are model outputs.
The assigned component properties and activity treatment influence the result. A simplified synthetic mixture is not a complete crude-oil assay.
Add transport before predicting deposits
A solid phase present in the bulk does not uniquely determine wall deposit thickness. Heat and mass transfer, shear, particle motion and residence time can matter.
The explorer displays recorded equilibrium solid fractions versus temperature. It does not label those values as deposition rate or blockage time.
Use compatible measurements
Wax appearance measurements and deposition-loop measurements test different parts of the physical problem. Matching one does not automatically validate the other.
Retain the thermal history and local wall conditions when moving from an equilibrium screen to a deposition study.
Explore the example
Recorded nonideal-multisolid-wax-equilibrium workflow. No deposition or field validation is claimed.
Select one of 31 recorded scenarios. Intermediate states are not interpolated.
Temperature (K) = 297.5. Total solid (mol/mol feed): 0; C18 solid (mol/mol feed): 0.
- Total solid (mol/mol feed)
- C18 solid (mol/mol feed)
Worked example
Recorded equilibrium solid amounts
Supported three-component synthetic regular-solution model at its documented default feed and solid properties; temperature spans 275–320 K. Full inputs are in JSON.
Relation and unit basis
Solid–liquid equilibrium satisfies the selected component chemical-potential conditions
The plotted solid amount is an equilibrium fraction, not a deposition rate or thickness.
1. Define the baseline
Temperature (K) = 297.5
Supported three-component synthetic regular-solution model at its documented default feed and solid properties; temperature spans 275–320 K. Full inputs are in JSON.
2. Select the relation
Solid–liquid equilibrium satisfies the selected component chemical-potential conditions
The plotted solid amount is an equilibrium fraction, not a deposition rate or thickness.
3. Substitute the values
Total solid at lower temperature = 0.313892178 mol/mol feed; C18 solid at lower temperature = 0.136655479 mol/mol feed; C20 solid at lower temperature = 0.177236698 mol/mol feed
Retain intermediate precision. The displayed values are rounded only after evaluation.
4. Read the result
Total solid (mol/mol feed) = 0; C18 solid (mol/mol feed) = 0
Equilibrium appearance does not determine wall transport, deposition kinetics or blockage time.
Result and interpretation
Total solid (mol/mol feed) = 0; C18 solid (mol/mol feed) = 0
Equilibrium appearance does not determine wall transport, deposition kinetics or blockage time.
Temperature selects recorded equilibrium states. The plotted quantity is solid amount, not deposit growth.
Study data and reproduction
Recorded nonideal-multisolid-wax-equilibrium workflow. No deposition or field validation is claimed.
| Temperature (K) | Total solid (mol/mol feed) | C18 solid (mol/mol feed) |
|---|---|---|
| 275 | 0.3138922 | 0.1366555 |
| 276.5 | 0.2972278 | 0.1247719 |
| 278 | 0.276984 | 0.1104035 |
| 279.5 | 0.2521941 | 0.09288898 |
| 281 | 0.2215308 | 0.07132118 |
| 282.5 | 0.1831194 | 0.04441932 |
| 284 | 0.1342203 | 0.0103122 |
| 285.5 | 0.1085174 | 0 |
| 287 | 0.09134744 | 5.5035e-17 |
| 288.5 | 0.07071537 | 1.0241e-16 |
| 290 | 0.04577644 | 2.2252e-16 |
| 291.5 | 0.01540888 | 0 |
| 293 | 0 | 0 |
| 294.5 | 0 | 0 |
| 296 | 0 | 0 |
| 297.5 | 0 | 0 |
| 299 | 0 | 0 |
| 300.5 | 0 | 0 |
| 302 | 0 | 0 |
| 303.5 | 0 | 0 |
| 305 | 0 | 0 |
| 306.5 | 0 | 0 |
| 308 | 0 | 0 |
| 309.5 | 0 | 0 |
| 311 | 0 | 0 |
| 312.5 | 0 | 0 |
| 314 | 0 | 0 |
| 315.5 | 0 | 0 |
| 317 | 0 | 0 |
| 318.5 | 0 | 0 |
| 320 | 0 | 0 |
Scroll the table to see all columns. The highlighted row is the worked baseline. Downloads retain full numerical precision.
Test your understanding
Work through the question before revealing its answer. Use the stated assumptions and include units in every numerical step.
1. Can an equilibrium solid fraction alone predict deposit thickness after one day?
Show the worked answer
No. A time-dependent deposition and transport model with appropriate boundaries is required.
2. Reproduce the baseline Total solid (mol/mol feed) without rounding intermediate values.
Show the worked answer
Total solid at lower temperature = 0.313892178 mol/mol feed; C18 solid at lower temperature = 0.136655479 mol/mol feed; C20 solid at lower temperature = 0.177236698 mol/mol feed. Total solid (mol/mol feed) = 0. Equilibrium appearance does not determine wall transport, deposition kinetics or blockage time.
3. Compare the first and last recorded scenarios. Which input changes?
Show the worked answer
Temperature (K) changes from 275 to 320. Other controls remain as stated in the premise. Total solid (mol/mol feed) changes from 0.313892178 to 0.
4. What would be needed to apply this example to a different physical system?
Show the worked answer
Replace the synthetic controls with compatible documented inputs and check the relation's assumptions. The plotted solid amount is an equilibrium fraction, not a deposition rate or thickness. Equilibrium appearance does not determine wall transport, deposition kinetics or blockage time.
Before using the result
- Label equilibrium rather than deposition outputs.
- Retain mixture and solid-property assumptions.
- Use suitable transport evidence for growth predictions.
Equilibrium appearance does not determine wall transport, deposition kinetics or blockage time.
Continue learning
Start with the broader workflow guide
Sources and method
The explanation and synthetic examples are original PetroCalcHub teaching material. The references below support the definitions and model context. They do not supply field validation for the synthetic scenarios.