Free Online Nodal Analysis Tool: IPR, VLP, and the Operating Point

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The teal curve is the inflow performance relationship, what the reservoir delivers at each bottomhole pressure. The orange curve is the vertical lift performance, the bottomhole pressure the tubing demands to move each rate to surface. The well produces where they cross. Change wellhead pressure or the friction coefficient and watch the operating point move: that movement is the value of every choke, compressor, and tubing decision.

Nodal analysis in your browser

A well is a negotiation between two systems: the reservoir, which delivers more fluid the harder you draw it down, and the tubing, which demands more bottomhole pressure the faster you push fluid through it. Nodal analysis plots both as curves against rate and reads the answer where they cross. The tool above solves that intersection live: choose a Vogel or straight-line inflow model, set the reservoir pressure and potential, describe the outflow with wellhead pressure, depth, fluid gradient, and a friction coefficient, and the operating rate and flowing bottomhole pressure appear on the chart. When the curves fail to cross, the tool says so plainly: the well cannot flow naturally and needs artificial lift.

Nodal analysis chart with the inflow performance relationship curve falling and the vertical lift performance curve rising, crossing at the operating point that sets the production rate
The well produces where the reservoir inflow curve meets the tubing outflow curve; every workover moves that crossing.

This is the third tool in the Reservoir Engineering Suite, and the one that turns the other tools into money: permeability and skin from the well test shape the inflow curve, and the operating point here is what they are worth in barrels per day.

The two curves

The inflow performance relationship comes from the reservoir. Above the bubble point it is nearly a straight line set by the productivity index; below it, gas breaking out of solution bends it, and the Vogel equation captures that curvature with one parameter. The vertical lift performance comes from the wellbore: the tubing must lift a column of fluid (the gradient times depth), overcome friction that grows with the square of rate, and still deliver the wellhead pressure the surface facilities demand. This tool uses that transparent three-term outflow rather than a black-box multiphase correlation, which keeps every number traceable, at the cost of the gas-lift curvature real VLP correlations show.

What to do with the crossing

  • Drop the wellhead pressure and the orange curve falls: the gain in rate is the value of a compressor or a bigger flowline.
  • Cut the friction coefficient to mimic larger tubing and read the acceleration directly.
  • Remove skin by rebuilding the inflow with a higher qmax from the well test tool: the rate difference is the stimulation prize.
  • If the curves are tangent or miss entirely, the well is dying: that is the artificial lift screening decision made visible.

What this tool is for

Screening workover and facility options, teaching the systems concept that underlies all production engineering, and quick checks of what a well should be doing versus what it is doing. Full nodal packages add multiphase flow correlations, temperature models, and choke performance; the logic of one falling curve meeting one rising curve is identical, and this page makes that logic instant.

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