Conventional petrophysics

The classic interpretation chain from the standard logging suite: shale volume, porosity, saturation, permeability and flow units — with chart-book methods and tool support for the main service contractors.

Pre-processing

• Alpha-SP, dGR and dNK pre-calculations.

Shale volume

• By GR — gamma-ray index with linear and non-linear (Larionov, Stieber) transforms.
• By density / neutron — shale volume from RHOB–NPHI separation.
• By resistivity — shale volume from resistivity index.

Porosity

• Density porosity — effective and total.
• Wyllie (sonic) — total and effective porosity from DT.
• Chart methods — neutron-density (GGKP-NK), neutron-gamma & caliper, and sonic-neutron charts.
• Fomenko method and neutron porosity (DNK) linear models.
• Neutron-porosity correction and matrix/fluid adjustments.

Saturation

• Saturation node — Archie with adjustable a, m, n, and water-resistivity inputs.

Permeability and flow units

• Permeability node — core-calibrated transforms from porosity.
• FZI — flow-zone indicator and flow-unit classification.
• Permeability from the volumetric model.

Lithology and cutoffs

• Lithology by cutoffs — litho- and pay-cutoffs applied per zone.

Post-processing

• Layering — split wells into beds / net-to-gross intervals.
• Squaring / averaging — block curves to bed resolution.
• Statistics by zones — summarised reservoir parameters.

Pre-calculations

• Formation-water resistivity from porosity — Archie–Dakhnov equation.
• Salinity / Rw — Arps–Batesman equations.

This page summarises the Petrophysics section of the Wellbore.AI / Gamma technical manual.

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