Saturation
The Saturation wizard estimates water saturation from a deep-reading resistivity log and a porosity log using industry-standard equations (Archie, Simandoux, and their shale-corrected variants). The output is a water-saturation curve bounded by 0 and 1 suitable for net-pay and reserves calculations.
The tool can be applied to a single well or in batch mode, allowing users to process all wells or selected wells from the Data Manager.
Launching the wizard
Open the Petrophysics ribbon bar and click Saturation. Choose the target well, select a method, supply the required input curves and constants, and preview the result in the chart before saving.
[image: placeholder_Saturation_wizard_main_window.png]
Input Parameters
- Well selection: Choose one well or enable Batch calculation to process multiple wells or a well group.
- Depth filter: The calculation interval can be limited by MD, TVD/TVDSS, or markers.
- Method: Select one of the equations described below. The parameter grid adapts automatically to the chosen method and disables any curves or constants it does not need.
- Input curves: True resistivity Rt (required), and depending on the method one of Total porosity or Effective porosity; plus shale volume Vsh for the shaly variants.
- Formation constants: Tortuosity factor a (default 1), cementation exponent m (default 2), saturation exponent n (default 2), formation water resistivity Rw (default 0.1 ohm·m), shale resistivity Rsh (default 3 ohm·m), and shale-correction exponent x (default 1.5, Indonesia method only). All constants are editable.
- Output curve: Name of the resulting water-saturation log. The name can be edited directly in the wizard before saving.
Calculation Methods
Pick the method that matches the lithology and the logs available. The Method panel displays the formula image and exposes only the parameters consumed by the selection.
Archie (Total porosity saturation)
The classical Archie equation applied to the total porosity curve. Assumes a clean, water-wet formation where conductivity is controlled by the brine in the pore network.
[image: placeholder_Archie_formula_—_total_porosity.png]
Inputs: Rt, total porosity, Rw, a, m, n.
Use: clean sandstones and carbonates with negligible clay content.
Simandoux (Effective porosity saturation)
Extends Archie with an additive conductive term that represents shale conductivity, applied to the effective porosity curve. Reduces the overestimation of water saturation in shaly sands that Archie produces.
[image: placeholder_Simandoux_formula.png]
Inputs: Rt, effective porosity, Rw, a, m, n, shale volume Vsh, shale resistivity Rsh.
Use: shaly reservoirs with dispersed clay where a quantitative Vsh curve is available.
Indonesia (Effective porosity saturation)
The Poupon–Leveaux "Indonesia" shaly-sand model, applied to the effective porosity curve. It combines the clean-sand and shale conductivity contributions through a Vsh-weighted term, which makes it more stable than Simandoux at high shale volumes. This is the only method that also uses the shale-correction exponent x.
[image: placeholder_Indonesia_formula.png]
Inputs: Rt, effective porosity, Rw, a, m, n, shale volume Vsh, shale resistivity Rsh, shale-correction exponent x.
Use: laminated or dispersed shaly sands, particularly where formation water is fresh and Simandoux becomes unstable.
Total shale (Total porosity saturation)
A total-shale model that adds a shale-conductivity term proportional to Vsh to the Archie response, evaluated on the total porosity curve.
[image: placeholder_Total_shale_total_formula.png]
Inputs: Rt, total porosity, Rw, a, m, n, shale volume Vsh, shale resistivity Rsh.
Use: shaly formations where a total-porosity reference is preferred and a Vsh curve is available.
Total shale (Effective porosity saturation)
The same total-shale model evaluated on the effective porosity curve, so the resulting saturation is referenced to the effective (non-clay-bound) pore space.
[image: placeholder_Total_shale_effective_formula.png]
Inputs: Rt, effective porosity, Rw, a, m, n, shale volume Vsh, shale resistivity Rsh.
Use: shaly reservoirs where effective porosity is preferred for reserves accounting.
Dual water (Total porosity saturation)
A dual-water model that distinguishes bound water associated with clay from free formation water, applied to the total porosity curve. It accounts for the extra conductivity of clay-bound water and gives more realistic saturations in clay-rich intervals.
[image: placeholder_Dual_water_formula.png]
Inputs: Rt, total porosity, Rw, a, m, n, shale volume Vsh, shale resistivity Rsh.
Use: clay-rich reservoirs where bound-water conductivity is significant and the total-porosity system is preferred.
Running and saving to Workflow
The wizard has a standard row of buttons along the bottom of the dialog:
- Save to workflow — adds the wizard, together with all of its current settings (selected wells, input and output curves, method, method parameters, user-defined constants, and output names), to the project Workflow as a task that can be re-run later.
- Run — executes the calculation with the current settings (this button replaces the former Calculate button).
- Save — stores the resulting curve in the well.
- Close — closes the wizard.
When a saved task is reopened from the Workflow panel, the wizard reopens with every stored setting restored, so it can be reviewed, edited, run, and saved back to the task. In this edit-from-workflow mode the bottom row shows Save and Cancel instead.
Results
The wizard produces a single water-saturation curve per processed well, clipped to the physical range 0–1. A preview chart plots the result against the input resistivity and porosity logs so the user can spot non-physical excursions before saving. Saved curves can be displayed in the Well log view and consumed by downstream tools such as Volumetric calculations.
Recommendations
- Calibrate a, m, and n against core-derived Sw or capillary-pressure data where available; default Archie values (a = 1, m = n = 2) rarely fit real rocks precisely.
- Use the Shale volume tool first to produce a reliable Vsh curve before switching to any of the shaly-sand methods (Simandoux, Indonesia, Total shale, or Dual water).
- For batch mode, ensure that every well in the group carries the required input curves; wells missing inputs will receive an empty output curve for the failing intervals.
See Also