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Archie Water Saturation from Resistivity Logs Calculator

Sw=[(aϕm)(RwRt)]1/nS_w = \left[\left(\frac{a}{\phi^m}\right)\left(\frac{R_w}{R_t}\right)\right]^{1/n}

Enter porosity, formation-water resistivity, true formation resistivity, and Archie constants. The calculator returns water saturation.

Tabular solver

Inputs

Defaults provide a quick field-unit example for the equation.

6 variables

Calculation runs locally with the shared TypeScript engine.

Formula reference

Archie water saturation estimates formation water saturation from resistivity-log measurements, porosity, formation-water resistivity, and Archie exponents.

View formula, units, and source

Assumptions

  • The rock is sufficiently clean for Archie behavior.
  • Formation-water resistivity and Archie exponents are representative.
  • Input resistivities use consistent temperature correction and units.

Common mistakes

  • Applying Archie directly to conductive shaly formations.
  • Using uncorrected water resistivity.
  • Assuming default Archie exponents are valid for every reservoir.