HELP: Save data as Log ASCII Standard (LAS) version 2.0 File

The LAS (Log ASCII Standard) is rapidly becoming the accepted industry standard for electronic transmission of digital wireline logs. Earlier digital formats were commonly coded in binary (such as LIS) and so required specialized software to read them. The LAS standard was introduced by the Canadian Well Logging Society⁽¹⁾ in 1989 to standardize the organization of digital log curve information for personal computer users. It did this very successfully and the standard became popular worldwide. Version 1.2 was the first version and followed in September 1992 by version 2.0 to address some inconsistencies. A more versatile version LAS 3.0 was released in 1999 however at present LAS 2.0 remains the dominant product. LAS 3.0 clarifies several of the poorly defined specifications of LAS 2.0 and provides expanded data storage capabilities, but has seen limited implementation.

This program will write a Log ASCII Standard (LAS) version 2.0 file.

The sections defined for the LAS 2.0 standard are as follows (see reference below for the complete document):

• "~V" (also known as "~VERSION INFORMATION SECTION") is a required section; has formatting requirements; must be the first section; identifies the version number and whether data is in "wrapped" or "un-wrapped" mode. The following are considered required fields in the ~Version information section for the LAS version 2.0 standard,

  ~Version Information
  Mnemonics	.Units	Value	: Description
  VERS	.	2.0	: CWLS log ASCII Standard -VERSION 2.0
  WRAP	.	NO	: One line per depth step

• "~W" (also known as "WELL INFORMATION SECTION") is a required section; has formatting requirements; is preferably the second section; contains information on the well name, location, and start and stop values of the data in this file. The following are considered required fields int the ~Well Information Section for the LAS version 2.0 standard,

  ~W(Well Information)
  Mnemonics	.Units	Value	: Description
  STRT	.F	nnnn.nn	: Start Depth
  STOP	.F	nnnn.nn	: Stop Depth
  STEP	.F	nnnn.nn	: Step Depth
  NULL	.	nnnn.nn	: Null Value; Common Null Values are -999.25, -9999, etc.
  COMP	.	aaaaaaaaaaaaaaaaaaaaaaaa	: Company Name
  WELL	.	aaaaaaaaaaaaaaaaaaaaaaaa	: Well Name
  FLD	.	aaaaaaaaaaaaaaaaaaaaaaaa	: Field Name
  LOC	.	aaaaaaaaaaaaaaaaaaaaaaaa	: Well Location
  PROV	.	aaaaaaaaaaaaaaaaaaaaaaaa	: Province; Canadian
  CTRY	.	aaaaaaaaaaaaaaaaaaaaaaaa	: Country; Outside Canada
  STAT	.	aaaaaaaaaaaaaaaaaaaaaaaa	: State
  CNTY	.	aaaaaaaaaaaaaaaaaaaaaaaa	: County
  UWI	.	aaaaaaaaaaaaaaaaaaaaaaaa	: Unique Well ID; Within Canada 16 character string
  API	.	aaaaaaaaaaaaaaaaaaaaaaaa	: API-Number
  SRVC	.	aaaaaaaaaaaaaaaaaaaaaaaa	: Logging Company
  LIC	.	aaaaaaaaaaaaaaaaaaaaaaaa	: Regulatory Licence Number
  DATE	.	aaaaaaaaaaaaaaaaaaaaaaaa	: Date logged, prefferred date MM/DD/YYYY

• "~C" (also known as ~CURVE INFORMATION SECTION") is a required section; has formatting requirements; contains curve mnemonics and their definitions in the order that they appear in the data section.
• "~P" (also known as ~PARAMETER INFORMATION SECTION") is an optional section; has formatting requirements; contains information on parameters or constants relevant to the wellbore such as mud resistivity, wireline engineer, truck number, elevation data, etc.
• "~O" (also known as "~OTHER") is an optional section; has no formatting requirements; contains other information or comments.
• "~A" (also known as ~ASCII LOG DATA") is a required section; has formatting requirements; is the last section in the file and also referred to as the data section. The index of the data columns is either Depth or Time. The index values always appear in the first column and each column of data must be separated by at least one space (ASCII 32). All values in the ASCII log data section must be floating point or integer (long) values. Other formats such as Text or Exponential values are not supported.

REFERENCE:
(1) Canadian Well Logging Society, LAS - Log ASCII Standard http://www.cwls.org/las_info.php

• LAS Version 2.0: Update July 2009 http://www.cwls.org/docs/las_20_updated_july2009.pdf
• LAS Version 3.0 (Adobe Acrobat File) http://www.cwls.org/docs/LAS_3_File_Structure.PDF

Author: John R. Victorine jvictor@kgs.ku.edu