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.

Neutron reading

Neutron log reading as volumetric porosity fraction.

V shale

Shale volume fraction from 0 to 1.

Shale reading

Neutron log reading in pure shale as fraction.

Correct a neutron porosity log reading (limestone porosity units) for shale content using V_shale times the shale neutron reading. 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]

Corrected porosity

Shale-corrected 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 Shale Volume Calculator

  Convert a gamma ray reading in API units to shale volume using the linear or Larionov transforms.

• Well Log Gamma Ray Index Calculator

  Linear gamma-ray index IGR = (GR - GR_clean) / (GR_shale - GR_clean) from log readings in API units; the standard first step toward Larionov-style Vshale estimates.

• 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.