Use this geological calculation for a transparent first-pass interpretation of measured rock, soil, fluid, well, stratigraphic, isotopic, geophysical, or seismic data under an explicitly selected model.

Rxo

Flushed-zone resistivity Rxo in ohm metres.

Rmf

Mud filtrate resistivity Rmf in ohm metres.

Sxo

Flushed-zone water saturation Sxo as a fraction.

m

Cementation exponent m.

n

Saturation exponent n.

a

Tortuosity factor a.

Invert the Archie equation in the flushed zone to estimate porosity from Rxo and mud-filtrate resistivity. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Phi xo

Flushed-zone porosity as a volume fraction.

• Log-derived porosity, shale volume, permeability, and saturation depend on tool type, borehole conditions, invasion, lithology, matrix and fluid properties, environmental corrections, calibration, and depth matching. Core and pressure data should constrain interpretation.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Compare independent measurements and models, retain units and analytical metadata, propagate uncertainty, and validate interpretations against logs, cores, maps, laboratory data, or field observations.

• Well Log Water Saturation Archie Calculator

  Invert the Archie equation for water saturation from true resistivity, formation water resistivity and porosity.

• Well Log Porosity Sonic Wyllie Calculator

  Apply the Wyllie time-average equation to a compressional sonic log, with optional shale correction, using slownesses in microseconds per metre.

• Well Log Permeability Wyllie Rose Calculator

  Estimate permeability in millidarcies from porosity and irreducible water saturation with the Wyllie-Rose power-law relation.