GEOX — RATLAS v0.1 Reference Atlas of Earth Materials

Typical Well Log Response Patterns — RATLAS v0.1 (Reference Only)

LITHOLOGY

GR [API]

CAL [in]

DEN [g/cc]

NPHI [v/v]

DT [μs/ft]

RT [Ωm]

Clean Quartz Sandstone

LOW 10–25

CLEAN

2.65

LOW 0.00

~55

HIGH 500+

Shale (Illite)

HIGH 80–150

SWOLLEN

2.45–2.70

HIGH 0.30–0.45

~90

LOW 8–15

Clean Limestone

LOW 5–15

CLEAN

2.71

LOW 0.00

~47

HIGH 1000+

Dolomite

LOW 5–15

CLEAN

2.87

LOW 0.04

~43

HIGH 2000+

Anhydrite

LOW 5

CLEAN

2.98

NEG −0.02

~50

VERY HIGH 50k+

Halite (Salt)

LOW 5

CLEAN

2.03

NEG −0.05

~67

EXTREME 100k+

Serpentinite

LOW 10

VUGGY

2.60

HIGH 0.30

~60

LOW 100

Coal / Lignite

LOW 40–60

CLEAN

1.10–1.50

HIGH 0.20–0.60

~100

HIGH 500–1000

Granite (K-feldspar)

HIGH 140–200

CLEAN

2.63–2.65

NEG ~0.01

~55

VERY HIGH 3k–5k

Basalt

LOW 15–30

CLEAN

2.95

LOW 0.03

~50

VERY HIGH 10k+

Material Families — 11 Families · 99 Canonical Cards

ALL 99

Showing 99 of 99 materials RATLAS v0.1 — reference only · not a classifier

SYMBOL

MATERIAL

ρm [g/cc]

NPHI [v]

GR [API]

RT [Ωm]

NOTES

Forward-Model Physics — Triple-Combo Reference

ρb — Bulk Density (Gardner Mixing Law)

Matrix + fluid linear mixing:

ρ_b = (1 − φ) · ρ_m + φ · ρ_f

ρ_b bulk density [g/cc] φ porosity [v/v] ρ_m matrix density [g/cc] ρ_f fluid mix density [g/cc]

Fluid fills: SW × ρ_w + (1−SW) × ρ_hc
Water ≈ 1.0 · Oil ≈ 0.85 · Gas ≈ 0.001–0.3

NPHI — Neutron Porosity (Hydrogen Index)

Fluid hydrogen index mixing:

NPHI ≈ φ · Σ(S_i · HI_i)

HI_w = 1.0 (bound water) HI_oil ≈ 0.95–1.0 HI_gas ≈ 0.25–0.35 S_i = saturation fraction

Limestone matrix scale · Negative NPHI = matrix-mineral effect (anhydrite, halite)
Gas effect: NPHI depressed relative to density porosity

RT — Resistivity (Archie, 1942)

Clean sand / carbonate:

R_t = a · R_w / (φ^m · S_wⁿ)

a = 0.62–1.0 (tortuosity) m = 1.5–2.2 (cementation exponent) n = 1.8–2.5 (saturation exponent) R_w = formation water resistivity

Shaly formations: Simandoux or Indonesia model with explicit C_sh
Steel/concrete: galvanic casing effect — do not apply Archie

VSH — Shale Volume (GR Linear)

Gamma ray index method:

V_sh = (GR_log − GR_min) / (GR_max − GR_min)

GR_log = measured API GR_min = clean sand baseline GR_max = shale baseline

Clavier (1971): V_sh = 1.7 − √(3.4 − I_GR)
Larionov older rocks: V_sh = 0.33(2^IGR − 1)

ΔT — Sonic Transit Time (Wyllie Time-Average)

Matrix + fluid addition:

ΔT = (1 − φ) · ΔT_ma + φ · ΔT_f

ΔT_ma matrix transit time [μs/ft] ΔT_f = ~189 (water) / ~220 (oil) / ~100 (gas) φ_s = sandstone total porosity (not shale-corrected)

Gas effect: ΔT inflated (slow) relative to density/neutron · Use for gas detection
Shale correction: φ_s = φ_total − V_sh · φ_sh

Symbolic Token Vocabulary — Geo-Reasoning Engine

These tokens encode lithology + fluid state for GEOX symbolic reasoning. Each token maps to physics constants in the RATLAS database. Not a classifier — reasoning agents interpret tokens in context.

SAND_QZ_CLEANClean quartz sandstone — Archie applies

SAND_ARKArkosic sandstone — K-feldspar increases GR

SAND_LITHLithic sandstone — rock fragments

SHALE_ILLIllite-rich shale — high NPHI, high GR

SHALE_SMCSmectite-rich shale — swelling clay, very high NPHI

SHALE_KAOKaolinite-rich shale — moderate NPHI, lower GR

SHALE_ORGOrganic-rich shale — high GR from U, low density

LIMESTONE_CCCalcite limestone — NPHI ~ 0 on limestone scale

DOLOMITE_DOLDolomite — denser than limestone, slight N-D sep

CHALK_MICChalk/micrite — high porosity, low density

ANHYDRITEAnhydrite — negative NPHI, very high density

GYPSUMGypsum — very high NPHI, low density

HALITERock salt — negative NPHI, lowest density

SYLVITEPotash salt — extremely high GR from K-40

CHERT_SILChert/flint — very low NPHI, high RT

COAL_BITBituminous coal — very low density, high NPHI

COAL_ANTAnthracite — higher rank, lower H

COAL_LIGLignite — lowest rank, high moisture

DIATOMITEDiatomite — biogenic silica, very high porosity

GRANITE_KK-feldspar granite — very high GR, radiogenic

RHYOLITERhyolite — volcanic equivalent of granite

PEGMATITEPegmatite — coarse K-feldspar, very high GR

BASALT_MAFBasalt — high density, low GR, high RT

GABBROGabbro — highest density of common igneous

DIABASEDiabase/dolerite — intrusive basalt texture

PERIDOTITEPeridotite — mantle slice, very high density

SERPENTINESerpentinite — altered peridotite, high NPHI

KIMBERLITEKimberlite — ultramafic pipe, diamond-bearing

SLATESlate — low-grade metamorphic, chlorite/mica

SCHIST_BTBiotite schist — mica foliation, high NPHI

GNEISS_FELSFelsic gneiss — banded, high GR from K-feldspar

GNEISS_MAFMafic gneiss — amphibole layers, high density

MIGMATITEMigmatite — partial melt fabric

MYLONITEMylonite — shear zone fault rock, fine-grained

QUARTZITEQuartzite — recrystallized silica, very high RT

MARBLE_CARMarble — recrystallized limestone

HORNFELSHornfels — contact metamorphic, dense

ECLOGITEEclogite — garnet-rich, very high density 3.45

SKARN_CXSkarn — calc-silicate metasomatite

GREENSCHISTGreenschist — chlorite/epidote, moderate NPHI

BLUESCHISTBlueschist — high-pressure assemblage

SILT_SATSaturated silt — fine-grained aquifer

CLAY_SATSaturated clay — very high NPHI, conductive

PEATPeat — organic, very low density

TOPOIL_ORGTopsoil — organic-rich, variable

LATERITE_FELaterite — Fe-oxide duricrust, tropical

LOESSLoess — wind-blown silt, homogeneous

CONCRETE_RFPortland cement — artifact marker, high RT

STEEL_FeSteel casing — FERRIC spike, very high RT

BRICK_CLAYFired clay brick — artifact marker

ASPHALTAsphalt — hydrocarbon binder, high H index

SLAGIndustrial slag — variable, often conductive

LANDFILLLandfill/waste — highly variable, organic