Multiphase and thermal model selection worksheet
PetroCalcHub · Original synthetic teaching exercise · 2026-10-24

Select a multiphase or thermal workflow by the physical question, required state variables and supported closure. A more complex solver is useful only when its assumptions match the problem.

Fixed controls: Inlet absolute pressure = 5 MPa; Constant absolute temperature = 320 K; Pipe inside diameter = 0.1 m; Length along flow = 200 m; Gas mass flow rate = 0.05 kg/s; Liquid mass flow rate = 5 kg/s; Constant liquid density = 850 kg/m3; Gas molecular mass = 20 kg/kmol; Constant gas Z-factor = 0.9 dimensionless; User-supplied constant Darcy factor = 0.02 dimensionless.

1. Which tool type is needed for a rapid valve-closure pressure history?

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2. Reproduce the baseline Total pressure drop (MPa) without rounding intermediate values.

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3. Compare the first and last recorded scenarios. Which input changes?

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4. What would be needed to apply this example to a different physical system?

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5. Calculate ideal Joukowsky pressure increment for ρ = 1,000 kg/m³, a = 1,000 m/s and Δv = 0.5 m/s.

Working: ________________________________________________


6. Does equilibrium wax appearance predict deposit thickness after a day?

Working: ________________________________________________


ANSWER KEY

1. A transient water-hammer model with wave speed and boundary conditions, rather than a steady pressure-loss calculator.
2. theta = 10 deg; with the fixed controls above, the workflow evaluates Total pressure drop = 0.253516638 MPa; Integrated friction loss = 0.01164336 MPa; Integrated hydrostatic loss = 0.241868043 MPa; Acceleration pressure loss = 0.00000523531475 MPa. Total pressure drop (MPa) = 0.253516638. One constant-ID interval, 0 to 90 degrees uphill from horizontal, constant phase masses, liquid density, Z, temperature and Darcy factor. Downhill flow, fittings and changes of direction/area are not supported. The zero-friction and single-phase options exist for limiting checks, not as recommended operating assumptions. All evaluated pressures must remain at least 0.1 MPa absolute, and the acceleration parameter must remain below 0.2, well away from the model's singular limit at one. These are conservative software bounds, not physical safety limits or a choking prediction. A successful numerical solve is not validation of no-slip behavior in a real petroleum system.
3. Uphill angle from horizontal (deg) changes from 0 to 30. Other controls remain as stated in the premise. Total pressure drop (MPa) changes from 0.0115943477 to 0.702225022.
4. Replace the synthetic controls with compatible documented inputs and check the relation's assumptions. Uphill angle from horizontal is varied within the supported input range. This is explicitly a homogeneous no-slip isothermal screening model, not Beggs-Brill, Hagedorn-Brown, drift-flux, a mechanistic flow-regime solver or three-phase PVT. It does not model slugging, slip, actual liquid holdup, gas liberation/dissolution, phase change, heat transfer, compositional properties or flow assurance. One constant-ID interval, 0 to 90 degrees uphill from horizontal, constant phase masses, liquid density, Z, temperature and Darcy factor. Downhill flow, fittings and changes of direction/area are not supported. The zero-friction and single-phase options exist for limiting checks, not as recommended operating assumptions. All evaluated pressures must remain at least 0.1 MPa absolute, and the acceleration parameter must remain below 0.2, well away from the model's singular limit at one. These are conservative software bounds, not physical safety limits or a choking prediction. A successful numerical solve is not validation of no-slip behavior in a real petroleum system.
5. ρaΔv = 500,000 Pa = 0.5 MPa. A full transient needs closure and boundary histories.
6. No. Deposition also needs transport, wall conditions, kinetics and removal assumptions.

Method: Original recorded synthetic cases solved with the site's homogeneous-multiphase-profile engine. The full inputs, outputs and diagnostic rows are in the downloadable JSON. These are discrete solved states; the lesson does not interpolate a new solve.
Sources:
LBNL T2Well: drift closure and coupled momentum balance: https://tough.lbl.gov/assets/docs/T2Well_ECO2N_Manual.pdf
NASA/TM-2019-220147: homogeneous momentum terms, section 4.1: https://ntrs.nasa.gov/api/citations/20190001795/downloads/20190001795.pdf
Tijsseling and Bergant: water-hammer waves and practical limits: https://atijssel.win.tue.nl/pdf_files/Tijsseling-Bergant_2018.pdf