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.
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, cementation exponent m, saturation exponent n, formation water resistivity Rw (ohm·m), shale resistivity Rsh (ohm·m), and shale-correction exponent x where applicable.
•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
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.
Inputs: Rt, total porosity, Rw, a, m, n.
Use: clean sandstones and carbonates with negligible clay content.
Archie — Effective porosity
Same Archie equation but driven by the effective porosity curve. Produces a water saturation referenced to the effective (non-clay-bound) pore space.
Inputs: Rt, effective porosity, Rw, a, m, n.
Use: formations where shale volume is known and effective porosity is preferred for reserves accounting.
Simandoux
Extends Archie with an additive conductive term that represents shale conductivity. Reduces the overestimation of water saturation in shaly sands that Archie produces.
Inputs: Rt, porosity, Rw, a, m, n, shale volume Vsh, shale resistivity Rsh.
Use: shaly reservoirs with dispersed clay where a quantitative Vsh curve is available.
Modified Simandoux
A variant that raises the shale term to the shale-correction exponent x, giving additional control over the strength of the clay-conductivity contribution in high-Vsh intervals.
Inputs: as Simandoux plus shale-correction exponent x.
Use: laminated or poorly sorted shaly formations where standard Simandoux still over- or underestimates Sw.
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 Simandoux or Modified Simandoux.
•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