LAS 2.0 Log Viewer
Open a LAS 2.0 file from your device to read the header and curves, and plot multiple depth tracks: gamma ray GR, resistivity on a log scale, and bulk density RHOB with neutron porosity NPHI.
This tool runs entirely in your browser: your data is not uploaded to any server. Free, no signup.
Educational tool for preliminary analysis. It is not a substitute for certified software or a qualified engineer’s review for major decisions.
File information
Curves
Explanation and formulas
LAS (Log ASCII Standard), published by the Canadian Well Logging Society (CWLS), is a text file made of sections starting with ~: version ~V, well ~W, curve definitions ~C, parameters ~P and data ~A.
The tool reads each header line as MNEM.UNIT DATA : DESCRIPTION, collects every number in ~A and splits them into records by curve count, so both WRAP NO and WRAP YES files work. The NULL value (usually −999.25) is treated as missing.
Tracks are chosen from common mnemonics: GR in track 1, resistivity (ILD, LLD, RT…) on a 0.2–2000 ohm.m log scale, and RHOB on 1.95–2.95 g/cc with NPHI on 0.45 to −0.15 (v/v), the standard limestone-compatible scale on which gas crossover shows.
~W STRT.M STOP.M STEP.M NULL. -999.25 WELL. ...
~C DEPT.M : depth GR.GAPI ILD.OHMM RHOB.G/C3 NPHI.V/V
~A 1670.000 45.2 12.3 2.35 0.21 ...
Resistivity track: x = log10(R), 0.2 – 2000 ohm.m
Density 1.95 → 2.95 g/cc ; Neutron 0.45 → −0.15 v/v
Validation
Validation: the data line of the CWLS LAS 2.0 specification example (depth 1670.000; DT, RHOB, NPHI, SFLU, SFLA, ILM, ILD = 123.450, 2550.000, 0.450, 123.450, 123.450, 110.200, 105.600) is read back exactly, −999.25 becomes missing, and the same file written in WRAP YES mode gives identical values. The tool’s example file is synthetic.
References
- Canadian Well Logging Society (CWLS). LAS Version 2.0: A Digital Standard for Logs (updated 2009). cwls.org.
- Asquith, G. & Krygowski, D. (2004). Basic Well Log Analysis, 2nd ed., AAPG Methods in Exploration 16.
- Schlumberger (2009). Log Interpretation Charts — density and neutron chart scales.