FLUIDS
A full equation-of-state workbench in the browser. Split the plus fraction, check the lab report, match the experiments by regression, then hand one tuned fluid to every other module and to your simulator.
WHAT IT DOES
Compositional PVT describes a reservoir fluid by its components and a cubic equation of state. You enter the composition from the lab report, with the plus fraction's molecular weight and specific gravity, and Converge splits the plus fraction into single carbon numbers, lumps them into pseudo-components and assigns critical properties and binary interaction parameters.
With the fluid described, Converge flashes it, traces the phase envelope and simulates the lab experiments: constant composition expansion, differential liberation, constant volume depletion, the multistage separator test and the swelling test. Each simulated table sits next to the measured one, so you can see where the model and the lab disagree.
Regression then adjusts the heavy-end, interaction and volume-shift parameters until the model reproduces the lab within the weights and bounds you set. The tuned model goes into the project's model library, and the one you pick becomes the project fluid that wells, reservoir, network and economics all read.
KEY CAPABILITIES
Choose the cubic equation that suits the fluid and your company's practice. All three carry the Peneloux volume shift, which corrects liquid density without moving the phase equilibrium.
The heavy end decides most of the fluid's behaviour, so every step of its description is visible and editable on the heavy-end split tab.
The flash is built to converge near the critical point, where gas condensates and volatile oils live.
Simulate the experiments in the lab report on the same basis the lab ran them, and run the studies a field development asks for.
Tune the model to the lab with control over what moves and by how much. Every run is kept, so you can compare runs and undo one.
Transport properties and screening checks come from the same fluid description, and the lab report is checked before any tuning starts.
WORKFLOW
Type or paste the mole fractions, the plus-fraction molecular weight and specific gravity, the reservoir temperature and the separator train.
Pick the split, the lumping scheme and the critical-property correlation, and review the pseudo-components and interaction parameters.
Run the data checks on the measured experiments, and exclude any point the checks or your judgement reject.
Trace the envelope and run the experiments. Each simulated table plots against the lab values.
Regress the parameters you choose, or move them by hand in live tuning, and compare runs side by side.
Save the model to the library, make it the project fluid, and export black-oil tables or a compositional deck.
VALIDATION
The equation-of-state engine is compared with an independent open-source thermodynamics code on published fluids, and pure-component behaviour with NIST reference data. A dash means the benchmark reports the agreement rather than a pass threshold.
| Check | Reference | Converge | Tolerance |
|---|---|---|---|
| Bubble and dew points, SPE5 oil and a gas condensate, Peng-Robinson and SRK | Independent open-source code | within 0.01% | — |
| Two-phase flash compositions | Independent open-source code | within 10⁻⁵ | — |
| Pure-component vapour pressures | NIST reference data | within 3% | — |
| Plus-fraction split keeps the C7+ molecular weight (V8) | 218.0 g/mol | 218.0 g/mol | 10⁻⁶ g/mol |
Not yet validated: a full phase envelope against a commercial package, and the minimum miscibility pressure calculation. The benchmarks page lists both.
INPUTS AND OUTPUTS
CONNECTED MODULES
The model you make the project fluid is the one every other module reads, so a change to the fluid shows up everywhere.
FAQ
Peng-Robinson 1976, Peng-Robinson 1978 and Soave-Redlich-Kwong. Each uses the Peneloux volume shift, which corrects liquid density without changing the phase equilibrium.
Yes. Bounded Levenberg-Marquardt regression adjusts the plus-fraction, critical-property, interaction and volume-shift parameters you select, with weights, bounds and point exclusion. A staged mode fits saturation pressure first, then phase behaviour, then viscosity, and live tuning lets you move parameters by hand.
By the Whitson three-parameter gamma distribution, out to C200 with mass conserved exactly. You then lump by equal mass, equal moles or custom ranges, and assign critical properties by Kesler-Lee, Riazi-Daubert, Twu or Pedersen.
A keyword-format compositional EOS deck, an EOS block in *-keyword format, separator-corrected black-oil tables (PVTO, PVDG, PVTW, or PVTG and PVTO for condensates) and RSVD and RVVD initialisation tables, in field or metric units.
Not yet. Hydrates are screened with the Motiee correlation and Hammerschmidt inhibitor depression, which is a screening check rather than a thermodynamic hydrate model. Wax and asphaltene models are not built.