| Quantity | Common units | What to check |
|---|---|---|
| Bulk density | g/cm³, g/cc; sometimes kg/m³ | 1 g/cm³ = 1,000 kg/m³. RHOB/RHOZ/DEN are candidate names, not guaranteed interchangeable channels. |
| Neutron porosity | v/v, decp, fraction; %, pu | 0.25 v/v = 25%. Sandstone and limestone calibration are different; multiplying by 100 does not convert the matrix basis. |
| Sonic slowness | µs/ft; µs/m | DT in µs/m = DT in µs/ft ÷ 0.3048. Check compressional versus shear channels. |
| Resistivity | Ω·m, ohmm, ohm.m | Use only positive values on a logarithmic scale. Check depth of investigation and tool type. |
| Gamma ray | API, gAPI | A baseline of 75 is a display choice for the example, not a universal shale cutoff. |
| Depth | m, ft | 1 ft = 0.3048 m. Measured depth, TVD and TVDSS are not interchangeable. |
No silent conversions
v4 does not convert measured values or neutron calibration. Log Viewer adapts some suggested limits when familiar units are recognised, but this only changes the display. If units are unknown, check the LAS header and source documentation before setting the scale. The scene format stores original curve IDs, mnemonics and units and rejects a mismatch.
Missing values and sampling
The parser reads the LAS NULL sentinel (default −999.25 if absent, with a warning). Missing values are excluded, never replaced with zero. Samples are paired by their source row in Crossplot. The viewer uses a detected depth curve and reports missing, reordered or duplicate depths. No resampling or depth matching across different files is performed.
Calibration and model assumptions
NPHI calibration is not automatically inferred by the API. Review the LAS parameter section, curve description and acquisition information. Our synthetic NPHI is sandstone-calibrated; that does not establish the basis of another LAS. Density–sonic overlays also need independent scales; curve separation is not a computed fluid indicator.
Density–neutron example and pitfalls · Synthetic model assumptions