GUIDE

Raster vs digital well logs

Scans and PDFs compared with LAS data

In short

A raster log is a picture. A digital log is a table of depth and curve values.
Only digital logs can be analyzed, crossplotted, computed on or loaded into interpretation software.
Digitizing converts the picture to values using the log’s printed scales.

Raster logs

A raster log is an image of a printed log: a scan, a TIFF, a PDF made from a scan, or a photograph. You can look at it and read approximate values, but the software holds only pixels.

Digital logs

A digital log is a table of depth and curve values, usually stored in a LAS file. Software can plot it with new scales, compute porosity or saturation, crossplot curves, and load it into interpretation packages.

Why convert raster logs

Older wells often exist only on paper or as scans.
Curve values let you compare old and new wells in one correlation chart.
Digital data can be used in calculations that a picture cannot support.

What digitizing involves

You calibrate depth and each curve using the printed scales, then trace the curve. The software converts the traced position to depth and value and exports the curves at a sampling interval you choose. See how to convert a scanned well log to LAS.

Limits to keep in mind

Accuracy depends on scan quality, calibration and tracing care, so check results against the scan.
Digitized curves carry the original log's own errors, such as depth shifts and hole effects.
Where a log is faded or a curve is hidden, the traced curve is an interpretation.