Well performance

#Overview

The Well performance module solves inflow (IPR) against outflow (VLP) for one well at a time. It reports every intersection and flags each one stable or unstable, traces the full pressure and temperature traverse, runs sensitivities, builds simulator lift tables, and matches the outflow correlation to your flowing well tests and gradient surveys. Use it to find a well's operating point, size tubing or lift, and hand lift curves to a simulator.

The page has eight tabs: Well data, IPR, VLP, Nodal, Gradient, Sensitivities, Lift tables and Matching.

#Inputs

Fluid properties come from the project fluid set on the PVT page. A new well takes its reservoir temperature and producing GOR from that fluid, and a gas-condensate project fluid gives a gas well. See Project fluid.

Every number follows your Field or Metric choice. Pressures are absolute: psia or bara.

#Well data

The survey, tubing, inflow model and its parameters start from typical values. Replace them with your own.

#IPR

Pick the IPR model and fill its parameters. Rates and pressures follow your unit system.

#Methods

#Inflow

Skin breakdown adds mechanical skin, damage (Hawkins 1956), deviation (Cinco-Ley et al. 1975), hydraulic fracture (Cinco-Ley and Samaniego 1981) and a non-Darcy D term. Multi-rate inflow test fits the model to measured rate and bottomhole pressure with Fit model to tests.

#Outflow

#Surface and lift

• Chokes: critical-flow form p = A·qL·R^B / d^C with Gilbert, Ros, Baxendell or Achong coefficients. Valid only while upstream pressure is at least 1.7 times downstream.
• Liquid loading: Turner, Hubbard and Dukler (1969) critical gas rate, with the 20 % upward adjustment.
• ESP: affinity laws scale rate with frequency and head with frequency squared.
• Temperature: linear profile, or Ramey (1962) steady-state heat transmission.

#Workflow

1. Open Well performance. On a project with no well, press Add a well.
2. On Well data, set Well type, reservoir pressure and temperature, ratios, the solution node, temperature model, wellhead boundary, outflow correlation, survey, tubing and lift.
3. On IPR, choose the IPR model and enter its parameters, or enter test points under Multi-rate inflow test and press Fit model to tests.
4. On VLP, set the Rate grid (Minimum rate, Maximum rate, Points) and check the Liquid loading panel for gas wells.
5. On Nodal, read the intersections and the curve table.
6. On Gradient, pick a Rate and plot pressure, temperature, holdup, velocity or gradient against MD or TVD.
7. On Sensitivities, pick a Sensitivity parameter and enter Sensitivity values. For a gas-lift well, read Gas-lift performance.
8. On Lift tables, set the Table axes and VFP table number, press Build table, then export.
9. On Matching, enter Flowing well tests, compare correlations, press Tune gravity and friction, enter a Gradient survey, and run Run Monte Carlo under Probabilistic rate.

#Interpreting results

• Tiles: Operating rate (with "stable intersection" or "unstable"), Flowing bottomhole pressure (with the angle between the curves), Absolute open flow (with total skin) and Pressure loss split.
• Intersections: the Nodal tab lists every crossing on the rate grid. A crossing on the falling, left-hand branch of the VLP is unstable; the operating point is the highest-rate stable crossing. With no crossing, the warnings above the chart explain why.
• Rate grid: if the inflow can deliver more than the Maximum rate, the curves are extended to the absolute open flow and the VLP tab tells you the new limit.
• Pressure loss: the Gradient tab splits bottomhole pressure into elevation, friction and acceleration. The dp/dz columns are in psi/ft or bar/m.
• Gas lift: Optimum injection maximises rate; Economic injection is where extra rate per unit gas falls to your Economic slope.
• Correlation comparison: for each correlation, Mean error (%), Absolute mean (%) and Std dev (%) against your well tests. The best one is marked Recommended. When it beats the one in use, a banner on the page offers Use [correlation] in one click.
• Probabilistic rate: P90 rate, P50 rate, P10 rate and the share of cases where the well Does not flow, with a rank correlation of each uncertain input against rate.

#Common pitfalls

#Exports

Lift-table axes are liquid rates (oil) or gas rates (gas), tubing head pressures, water cuts or water-gas ratios, GORs or CGRs, and lift-gas rates. Other lift-table keyword formats are not available yet.

#Related

• Project fluid
• Black-oil PVT
• Surface network
• Simulation
• Integrated forecast