VFP lift curve builder

VfpTableBuilder (package neqsim.process.fielddevelopment.reservoir) builds a VFPPROD or VFPINJ table from a pluggable lift model. It owns the axes, the evaluation of the model at every coordinate, rate caps, repair of infeasible points, physical sanity enforcement, diagnostics and the deck text with a provenance header. Deck formatting and unit conversion are delegated to EclipseVFPExporter (see the export contract). The method guide for engineers and agents is the skill neqsim-vfp-lift-curves.

Building blocks

Class Role
VlpProvider Single-method interface: flowing pressure at datum for rate, outlet pressure, water ratio, gas ratio and ALQ
TubingVlpProvider Deviated tubing survey (TubingPerformance.setSurvey) with an inlet-pressure solve for the wellhead pressure
ForwardVlpProvider Turns any forward model (outlet pressure from inlet pressure: pipes, valves, a process) into a provider by inverse solve
RecombinationFluidFactory Recombines surface gas, stock-tank liquid and water to the well stream for each coordinate
VfpTableBuilder Axes, evaluation, rate cap, sanity enforcement, deck text
VfpDeckReader Parses a VFPPROD/VFPINJ keyword back to numbers, for round-trip checks

Gas well example

RecombinationFluidFactory wellStream = new RecombinationFluidFactory(template, surfaceGas, condensate)
    .setRateBasis("GAS").setWaterRatioType("WGR").setGasRatioType("OGR");
TubingVlpProvider vlp = new TubingVlpProvider(wellStream, new double[] {0.0, 1500.0, 3200.0},
    new double[] {0.0, 1450.0, 2500.0}, new double[] {0.15, 0.15}).setTemperatures(95.0, 40.0)
    .setNumberOfSegments(6).setCorrelation(TubingPerformance.CorrelationType.GRAY);
VfpTableBuilder.Result result = VfpTableBuilder.gasWell(1).setDatumDepth(2500.0)
    .setRates(VfpTableBuilder.rateAxis(0.2e6, 1.0e6, 5, 1.2))
    .setOutletPressures(VfpTableBuilder.pressureAxis(40.0, 80.0, 4, 0.1, 0.1))
    .setWaterRatios(new double[] {1.0e-6, 1.0e-4}).setGasRatios(new double[] {1.0e-5, 1.0e-4})
    .setRateMonotoneMode(VfpTableBuilder.RateMonotoneMode.FULL).setRateCap(1.1e6, 200.0)
    .addProvenance("Gray tubing survey, synthetic well").build(vlp);
result.writeDeck(java.nio.file.Paths.get("vfp1.inc"));

This example is exercised by VfpTableBuilderTest.documentedGasWellExampleRuns; the round trip, off-grid accuracy, rate cap, failure policy and monotonicity behaviour are covered by the other tests in the same class.

Sanity rules

The builder applies these rules in order and reports every repair in Result.getWarnings():

  1. The flowing pressure is not below the outlet pressure: $p_{wf} \ge p_{thp}$.
  2. The flowing pressure increases with the outlet pressure with slope at least $m_{min}$ (default 0.5 bar/bar).
  3. Rate dependence: ABOVE_MINIMUM (default) keeps the liquid-loading side of a J-shaped gas curve and makes the rest non-decreasing; FULL makes the whole curve non-decreasing, which OPM Flow needs to avoid flipping between rate and THP control.

A rate cap $Q_c$ replaces the pressure above the cap by a penalty slope:

\[p_{wf}(Q) = p_{wf}(Q_c) + \lambda \left(\frac{Q}{Q_c} - 1\right), \quad Q > Q_c\]

where $\lambda$ is the penalty in bar per 100 percent above the cap.

Interpolation check

Result.interpolate(...) reproduces the multilinear interpolation of the simulator, so off-grid accuracy can be checked against a direct provider solve before the deck is used.

Python

examples/neqsim/process/vfp_gas_well_lift_curve.py runs the same synthetic gas well through jpype with the workspace classes (neqsim_init) and writes the include file. A custom lift model in Python implements VlpProvider with jpype.JImplements; see the skill neqsim-vfp-lift-curves.