Vertical Drift-Flux Gas-Liquid Pressure Profile Calculator

Calculation sequence

1. Supply separate gas and liquid mass rates at a measured inlet absolute pressure. The interval must be vertical and upward with both phases co-current. Gas density follows p*M/(Z*R*T) with fixed temperature and Z; liquid density is fixed. Use calibrated C0, upward drift velocity and Darcy friction factor for the actual fluid, diameter and flow regime. The defaults are synthetic, not recommended closure coefficients.
2. At each pressure, superficial rates determine gas velocity, void fraction, liquid velocity and holdup-weighted density. Gas and liquid velocities differ when C0 exceeds one or drift velocity is positive. Liquid holdup is not the liquid inlet-volume-flow fraction. The wall term uses the holdup density and mass-average mixture velocity, consistent with the cited T2Well friction convention; its Fanning factor is converted to Darcy by multiplying by four.
3. The pressure integrator includes the derivative of the sum of phase momentum fluxes, not the no-slip acceleration formula applied to a slipped density. Friction and hydrostatic components are integrated separately. The endpoint pressure drop must equal their sum plus the change in phase momentum flux, and a tighter-tolerance integration must agree before results are accepted.
4. Compare the drift-flux curve with a separate vertical no-slip curve using the same mass rates, properties, geometry and Darcy factor. Setting C0 = 1 and drift velocity = 0 recovers that reference. CSV includes all 51 axial stations, holdup, both velocities and pressure components. Both curves must remain in their supported pressure and acceleration envelopes; otherwise no partial comparison is published.

Worked check

The synthetic defaults use a 0.1-m pipe, 200-m upward interval, 5-MPa inlet, 320 K, gas/liquid rates 0.05/5 kg/s, liquid density 850 kg/m3, M = 20 kg/kmol, Z = 0.9, Darcy factor 0.02, C0 = 1.2 and drift velocity 0.3 m/s. Outlet pressure is about 3.525611 MPa versus 3.627851 MPa without slip. Outlet liquid holdup is about 0.851738; gas/liquid velocities are about 1.458189/0.879336 m/s. The added hydrostatic loss is model-dependent, not a claim that slip always increases pressure loss.

Synthetic examples for reproducibility, not measured field results.

Assumptions and limitations

• Steady, vertical upward, co-current, isothermal gas/liquid screening only. No downward, counter-current, horizontal or inclined slip model; no regime selection, empirical Shi/Hagedorn-Brown/Beggs-Brill implementation, phase flash, dissolution, heat transfer, slug transients or reservoir coupling. This is a reduced model, not the full T2Well simulator.
• C0, drift velocity, Z, Darcy factor and liquid density remain constant over the interval. The wall-friction closure is one specified mixture approximation, not a universal multiphase friction correlation. A Darcy factor must not be entered as a Fanning factor. Field use requires independent calibration and validation; numerical balance alone is not accuracy evidence.
• Software envelopes: 1 <= C0 <= 1.5, 0 <= drift velocity <= 3 m/s, positive rates for both phases, gas less dense than liquid, pressure >= 0.1 MPa absolute and 0 < gas void fraction <= 0.95 throughout. Both profiles must have acceleration parameter below 0.2; choking and near-critical solutions are rejected, not extrapolated. These are implementation limits, not universal correlation ranges.

Sources and maintenance

Published by PetroCalcHub Team. Implementation and source checks: 2026-10-14. This does not claim independent expert review.

• LBNL T2Well/ECO2N manual (2011): drift closure equations 7-9; phase momentum and mass-average wall-friction closure, Appendix A1-A5
• IAEA TCS 69 (2019), printed pages 50-52: drift/slip versus homogeneous assumptions and mixture momentum; not a petroleum flow-regime calibration

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