Wellhead compression: what the reservoir gives and what it costs to move — a PENG-ROBINSON process flowsheet
A gas well is not a feed whose flow you type in. The rate is an OUTCOME of how hard the facility pulls on the reservoir, and this example starts there. The well runs the Vogel inflow-performance relationship: at a 250 bar reservoir pressure and a 5e-5 mol/s/Pa productivity index its absolute open flow is J x p_r / 1.8 = 694 mol/s, and the fraction of that you actually get follows 1 - 0.2(p_wf/p_r) - 0.8(p_wf/p_r)^2. Holding 180 bar at the bottomhole delivers 306 mol/s, 44% of open flow. Squeeze to 150 bar and it rises to 411; back off to 240 and it collapses to 49. The curve is deliberately not a straight line — that curvature is why compression pays for itself, and why the last increment of drawdown buys less than the first. Compression is where the stage count earns its keep. Taking that gas from 30 to 150 bar in ONE stage lands the discharge at 508 K (235 C) — past what reciprocating machine valves and lube oil tolerate, before any efficiency argument. Split it into three with intercooling to 313 K and the discharge is 362 K; four stages give 349 K. The temperature, not the power, is what sets the stage count on a real machine. Read the reported duty carefully. duty on this unit is the NET of the compression work and the intercooler heat removed, summed into one number — it goes from +2094 kW at one stage to -384 kW at three, not because compression got cheaper but because there is now intercooling to subtract. It is not shaft power, and this example does not present it as such.
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- Rigorous PENG-ROBINSON thermodynamics, solved by the same engine every simulation runs on.
- 2 unit operations modeled: WELL, COMP.
- Focus areas: Upstream, Well, IPR, Vogel, Compression, Gas processing.
- Thermodynamics
- PENG-ROBINSON
- Components
- methane, ethane, propane, co2
- Unit operations
- WELLCOMP
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Read the step-by-step guideReproduce this exact result from Python — the real client.get_example() → run_and_wait() path, not a mockup.
from flowsim.sdk import FlowSimClient
client = FlowSimClient()
example = client.get_example("wellhead-compression")
sim = client.create_simulation(example["title"], example["flowsheet"])
result = client.run_and_wait(sim["id"])
print(result["status"]) # "converged"
streams = client.streams(sim["id"])Related models
Gas compressor air-cooled aftercooler (fin-fan)
A natural-gas booster compressor followed by an air-cooled (fin-fan) aftercooler — the standard way to reject compression heat where no cooling water is available. The compressor raises the gas from 8 to 24 atm (hot discharge ~150 °C); the air cooler then rejects that heat to ambient air, cooling the gas back to 49 °C. Unlike a plain cooler, the air_cooler op closes the air side: from the process duty and the 35 °C design ambient it solves the air mass flow (a 15 °C air rise) and reports the fan power from the given fan static pressure. Honest scope: screening air-side model (fixed cp_air, ideal-gas air density, no fin/row geometry rating); an air cooler cannot cool below ambient, so the 49 °C target sits safely above the 35 °C air inlet.
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The raw NGL recovered by a cold separator is fractionated: a depropanizer column splits it into a C₃-and-lighter overhead (propane + a little ethane, the LPG product) and a C4+ bottoms (butanes + natural gasoline). The column is solved with the component-flow Naphtali-Sandholm MESH (method "ns"), which carries every component flow as an unknown so the feed-vs-products material balance is an equation the solver closes by construction — the right tool for a sharp C₃/C₄ cut, where a reduced-form column would drag the split off and leak a few percent of a component. Peng-Robinson handles the light-hydrocarbon VLE; the built-in sensitivity sweeps the reflux ratio against the reboiler duty (the classic distillation energy trade-off).