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MODULE GUIDES

Simulation

Fully implicit three-phase black-oil simulator on Cartesian or radial grids, with Peaceman wells, schedules, group control and deck import and export.

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Overview

The Simulation module runs a fully implicit three-phase black-oil reservoir simulator in the browser. You build a case on Cartesian or radial grids, or import a keyword-format simulator deck, then run it and read field and well results, pressure and saturation maps, and a convergence report that explains every time-step cut. Use it for sector models, pattern studies, coning and near-well models, and checks on simple full-field models up to 400,000 cells.

The page opens on the SPE1 case (Odeh 1981) in the sample field. The tabs are Grid & properties, Fluids & rock, Initialisation, Wells & schedule, Run and Results.

Inputs

Grid & properties

Input Unit (Field) Notes
Geometry – Cartesian or Radial (r-θ-z)
Cells in x, Cells in y (or Radial cells, Angular sectors), Layers count Up to 200 layers; 400,000 cells in total
Cell size x, Cell size y ft Cartesian
Wellbore radius, Outer radius ft Radial
Top depth ft
Rock Compressibility, Reference pressure 1/psi, psia Pore-volume compressibility
Per layer: thickness, porosity, kx, ky, kz ft, fraction, md Layers table
Vary permeability and porosity cell by cell – Log-normal field with Dykstra-Parsons coefficient, Seed and Correlation length i, j, k (cells)

Fluids & rock

Input Notes
Fluid source SPE1 tables (Odeh 1981) or Project fluid (PVT page)
Saturation function Model SPE1 tables or Corey curves
End points Connate water, Residual oil to water, Residual oil to gas, Critical gas (fractions)
Maxima and exponents krw max, kro max, krg max, nw, now, nog, ng
Capillary pressure Pcow at Swc, Pcgo at max gas (psi), Pc exponent
Three-phase oil Saturation weighted (default), Stone I (normalised, Fayers-Matthews Som), Stone II, Baker (1988)

Initialisation

Method Inputs
Gravity equilibrium from contacts Datum depth (ft), Pressure at datum (psia), Gas-oil contact, Water-oil contact (ft), Solution GOR (scf/STB)
Uniform state Pressure (psia), Water saturation, Gas saturation, Solution GOR

Wells & schedule

Input Notes
Well type Producer or Injector; injectors take an Injected phase: Water or Gas
Completion Column i, Row j, First layer, Last layer, Wellbore radius (ft), Skin
Controls Rows of From day, Control mode and Target, with a BHP limit (psia). Modes: Oil rate, Water rate, Gas rate, Liquid rate, Reservoir rate, Bottom-hole pressure, Shut
Schedule Years to simulate, Reports per year
Group control and economic limits Field oil target (0 = none), Shut a producer below oil rate (0 = off), Shut above water cut (0 = off), Shut above GOR (0 = off)
Numerics First time step, Maximum time step (days), Newton iterations, Saturation change target, Pressure change target (psi), Linear solver: ILU(0) BiCGSTAB or ILU(0) GMRES(30)

Methods

  • Formulation: fully implicit black oil with oil, water and gas equations, solved by Newton's method with automatic differentiation. Primary variables are pressure, water saturation, and gas saturation or solution GOR, switched by phase state.
  • Linear solvers: ILU(0)-preconditioned BiCGSTAB or GMRES(30).
  • Wells: Peaceman well index, with rate or bottom-hole pressure control and a BHP limit.
  • Group control: a field oil-rate target shared between producers by well potential. Well economic limits on oil rate, water cut and GOR. A well shut by a limit stays shut until a later control change in its schedule reopens it.
  • Three-phase relative permeability: saturation-weighted, Stone I with the Fayers-Matthews Som, Stone II and Baker. Stone I and Baker are checked against hand calculations and end-point limits.
  • Heterogeneity: log-normal permeability with Gaussian correlation, set by the Dykstra-Parsons coefficient.
  • Time stepping: adaptive steps aimed at the saturation and pressure change targets, with cuts when Newton fails.
  • Deck reader and writer: DIMENS, DX/DY/DZ (and DXV/DYV/DZV), TOPS, PORO, PERMX/PERMY/PERMZ, ACTNUM, ROCK, PVTO, PVDG, PVTW, DENSITY, SWOF, SGOF, EQUIL, RSVD, DRSDT, FIELD/METRIC, WELSPECS, COMPDAT, WCONPROD, WCONINJE, TSTEP and END. METRIC decks are converted on read.
  • Validation: the built-in SPE1 case reproduces the published comparative solution. See Benchmarks.

Workflow

  1. Open Simulation. Start from the sample field (Open the sample field), import a deck (Import a simulator deck or Import deck), or edit the built-in case.
  2. On Grid & properties, set geometry, cell counts and sizes, top depth, rock compressibility and the Layers table.
  3. On Fluids & rock, pick the Fluid source and saturation-function Model. Check the relative permeability and capillary pressure curves.
  4. On Initialisation, choose a Method and set contacts or a uniform state. The Column panel shows whether the gas cap and aquifer fall inside the grid.
  5. On Wells & schedule, add wells, completions and control rows. Set Years to simulate, group control, economic limits and numerics.
  6. On Run, press Run simulation. Watch the convergence table: step size, Newton and linear iterations, worst residual, worst material-balance error and outcome.
  7. On Results, read the headline tiles and charts. Use Maps to step through Pressure, Sw, Sg or Rs by Time and Layer.

Interpreting results

  • Oil in place, initial, Cumulative oil (with recovery factor), Cumulative gas and Final average pressure sum up the run.
  • Check Worst material balance on the Run tab. It is a fraction of pore volume and should be very small. Many time-step cuts, or Newton iterations near the limit, mean the numerics or the inputs need attention.
  • The charts show field oil, water and gas rates, producing GOR, water cut, average reservoir pressure, cumulative production, well bottom-hole pressures and well oil rates.
  • Per-well tables show the active control at each report, so you can see when a well switched from rate to BHP control.
  • Rates below round-off of a well's liquid rate are reported as zero.

Common pitfalls

Exports

  • Export deck downloads the current case as a keyword-format .DATA file.
  • The CSV button on Field liquid rates and Field results downloads field results as sim-field.csv.