Log ASCII Standard
Encyclopedia
Log ASCII Standard is a standard file format
common in the oil and gas
industry to store wellbore log information. Well logging
is used to characterize subsurface stratigraphy
in a wellbore.
A single LAS file can only contain data for one wellbore but it can contain any number of curves for that well. Common curves found in a LAS file might be gamma ray logging
, sonic logging
, or resistivity logging
.
One of the restrictions of the LAS format is that data must be saved in the same interval. This usually is not an issue with most log curves.
File format
A file format is a particular way that information is encoded for storage in a computer file.Since a disk drive, or indeed any computer storage, can store only bits, the computer must have some way of converting information to 0s and 1s and vice-versa. There are different kinds of formats for...
common in the oil and gas
Petroleum industry
The petroleum industry includes the global processes of exploration, extraction, refining, transporting , and marketing petroleum products. The largest volume products of the industry are fuel oil and gasoline...
industry to store wellbore log information. Well logging
Well logging
Well logging, also known as borehole logging is the practice of making a detailed record of the geologic formations penetrated by a borehole. The log may be based either on visual inspection of samples brought to the surface or on physical measurements made by instruments lowered into the hole...
is used to characterize subsurface stratigraphy
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
in a wellbore.
A single LAS file can only contain data for one wellbore but it can contain any number of curves for that well. Common curves found in a LAS file might be gamma ray logging
Gamma ray logging
Gamma ray logging is a method of measuring naturally occurring gamma radiation to characterize the rock or sediment in a borehole. It is sometimes used in mineral exploration and water-well drilling, but most commonly for formation evaluation in oil and gas well drilling . Different types of...
, sonic logging
Sonic logging
Sonic logging shows a formation’s interval transit time, designated Dt. It is a measure of a formation’s capacity to transmit sound waves. Geologically, this capacity varies with lithology and rock textures, notably porosity....
, or resistivity logging
Resistivity logging
Resistivity logging is a method of well logging that works by characterizing the rock or sediment in a borehole by measuring its electrical resistivity. Resistivity is a fundamental material property which represents how strongly a material opposes the flow of electric current...
.
One of the restrictions of the LAS format is that data must be saved in the same interval. This usually is not an issue with most log curves.
External links
- Canadian Well Logging Society: LAS files, accessed 24 January 2009.
- version 3 file format specification, accessed 21 March 2009.
- US Geological Survey: Log ASCII Standard (LAS) files for geophysical wireline well logs and their application to geologic cross sections through the central Appalachian basin, accessed 24 January 2009.