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.

Delta t log

Compressional sonic slowness from the log in microseconds per metre.

Delta t matrix

Matrix slowness in microseconds per metre.

Delta t fluid

Pore-fluid slowness in microseconds per metre.

V shale

Shale volume fraction from 0 to 1.

Delta t shale

Shale slowness in microseconds per metre.

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

Porosity

Wyllie time-average 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 Simandoux Calculator

  Solve the Simandoux shaly-sand equation for water saturation including shale-conductivity correction.

• Well Log Permeability Wyllie Rose Calculator

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

• Well Log Porosity Density Calculator

  Density-log porosity phi_D = (rho_ma - rho_b) / (rho_ma - rho_f) from bulk, matrix and pore-fluid densities in kilograms per cubic meter; the standard formation-density porosity relation.