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 result is a water-saturation curve written on the scale of the selected output unit (fraction by default), 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, markers, or zones. On the Zones range tab, select one or more zones of a zone set; a selected zone that does not exist in a well is skipped for that well.
- Method: Select one of the equations described below. The parameter grid adapts automatically to the chosen method: the curves and constants that the method does not use are hidden.
- 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. Curve Total porosity, Curve Effective porosity and Curve Shale volume each have their own unit list; set it to fraction or % to match how the log is stored. Curve Resistivity has no unit list: it shows a fixed ohm×m unit label.
- 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 is filled in automatically from the selected method, in the form Saturation - <method name>, and it is refilled every time the method is changed. The name can also be edited directly in the wizard before saving; because a change of method replaces a name typed by hand, enter a custom name last. The row also has its own unit list, which sets the scale of the result: fraction (the default) writes the water-saturation values on the 0–1 scale, while % writes them in percent and stores % as the unit of the saved curve.
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. The value returned by the selected equation is stored as it is, on the scale of the chosen output unit: fraction (the default) writes it on the 0–1 scale, and % on the 0–100 scale. No lower or upper limit is applied, so unsuitable input curves or constants can produce values outside that scale. A preview chart plots the result against the input resistivity and porosity logs, so check it for 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. A well whose required curve is missing is skipped, and the wizard names that well and the missing input in the message shown when the run finishes.
See Also