October 13, 2009

Office of Groundwater Technical Memorandum 2010.01

Subject: PROGRAMS AND PLANS — Update of the National Policy to Archive Borehole-Geophysical Logs

In 2000, a national policy to archive borehole-geophysical logs was established by OGW Technical Memorandum 00.03. Since that time, the Log ASCII Standard (http://cwls.org/las_info.php) has become the accepted format for storage and transmittal of log data in the geophysical and groundwater science community.  All widely used software for geophysical log collection and analysis now automatically generates and reads LAS-formatted data.   Although the present archive policy allows for archive of log data in other ASCII formats, the current situation strongly indicates that LAS should become the standard format for log archival within the USGS.  This memorandum updates OGW Technical Memorandum 00.03 and establishes a new requirement that geophysical logs be archived on the USGS Water Science Center’s computer database in LAS format.   This memorandum clarifies archiving of image-log data, log-type codes, corrections/shifts/post processing, log annotations, and NWIS Logs records. This memorandum introduces a web-based system to be used for the proper archiving of log data files and headers. 

LAS Formatted Logs:
Borehole-geophysical logs are to be archived in LAS 2.0 unwrapped format as one the following groups of log types:

  1. Individual log of a single parameter collected with a single probe (such as a caliper log);
  2. Combination log of multiple depth-adjusted parameters collected with a single probe (such as a multi-function electric log); or
  3. Composite logs of multiple depth-adjusted parameters collected with multiple probes that have been depth corrected.

As policy, an NWIS site must be established for each logged borehole.  Geophysical logs should be archived by the Water Science Centers on a locally-based computer system under a main directory called LOGARCHIVE.  Subdirectories for each NWIS 15-digit Site ID number, as previously required, are no longer needed.   Each geophysical log file name will include the NWIS 15-digit Site ID number, date of log collection (year month day), two-letter log-type code, and a sequence number.  In addition, the file name will include the “.LAS” extension to indicate it is archived in LAS format. The first log of the same type collected on a particular day would have a sequence number of 01, the second, 02, etc.  An example path name for an archived log would be:

LOGARCHIVE>424531077564201.20000601.MI01.LAS

Image-Log Data:
Image-log data from acoustic- and optical-televiewers are not conducive for conversion to the LAS format, so they should be archived in their original binary format and if desired in commonly used image formats such as jpeg, tiff, or PDF.  An executable file of any software needed for analysis of original binary formatted geophysical log files should be included in the LOGARCHIVE with explanation of security measures for proprietary programs.  Files archived in an original binary format should be archived with the same naming convention as a LAS file except that it will include the file extension assigned by the software manufacturer (.log or .rd for example).  The file naming convention for extracted images (jpeg, tiff) and PDFs will use a zero date, must be sequentially numbered (IMG01 … IMG02, PDF01 … PDF02) and include the proper extension depending on the type of file archived. Examples of archived files would be:

LOGARCHIVE>424531077564201.20000601.AT01.log (acoustic televiewer archived as an original binary file)
LOGARCHIVE>424531077564201.00000000.PDF01.pdf (the first PDF file archived for this site)
LOGARCHIVE>424531077564201.00000000.IMG01.jpg (the first image file archived for this site)

Log-Type Codes:
The master list of geophysical log-type codes is available from the OGW internal web page (http://water.usgs.gov/usgs/ogw/bgas/borehole_archiving/).  All efforts should be made to properly categorize the log into one of these existing log types.  Requests for additional log types should be directed to the OGW Borehole Geophysics Advisor (jhwillia@usgs.gov)

Corrections/Shifts/Post Processing
Borehole-geophysical logs archived in the Water Science Center’s database should be the final corrected version of the logs.  All corrections, depth shifts, and post processing must be complete to assure the log is referenced to the designated measuring point and that the data are complete and accurate.  If necessary, any notes on post processing can be included in the remarks field of the log header.

Log Annotations
The condition of the borehole (mud- or water-filled for example) and size of the hole at the time of logging should be noted in the remarks or hydrologic conditions section of the log header.  This information is critical for log analysis and interpretation.  In addition, any conditions that influence depth-specific log data should noted along with the depth of the occurrence.  For example, if a caliper tool sticks and the diameter readings are influenced, then a notation for that depth should be made.  If numerous depth-specific annotations are required, then a posting text file can be archived along with the borehole logs to provide additional information.  New software has been developed for log annotations.

NWIS Logs Records
A log record must be entered into NWIS for each borehole-geophysical log archived in the Water Science Center’s database.  These records are not automatically added but are necessary to assure conformity with NWIS architecture.  New software has been developed for generating the logs records.

Web-Based Archiving System:
A new USGS web-based system has been developed for archiving LAS files as well as addressing many of the issues described in this memorandum.  Users can access the system from the following URL:  http://logarchiver.usgs.gov .  The web-based system should be used to archive newly collected geophysical logs and to transfer existing logs archived in each Centers’ computer database to the approved format.  Through the application of the web-based system and associated software, the OGW will assist each Center in the transfer of their geophysical logs that have been previously archived following the guidelines presented in OGW Technical Memorandum 00.03.

Header templates for the widely used WellCAD log-analysis software are available from the OGW internal web page (http://water.usgs.gov/usgs/ogw/bgas/borehole_archiving/).  The templates are interfaced with the new USGS web-based system to generate LAS-compatible headers for individual, combination, and composite log archives in English or metric units.

The Regional Groundwater Specialists are to act on behalf of the Office of Groundwater to assure that the borehole-geophysical logs collected by the Water Science Centers are properly archived.

Adherence to the updated policy of archiving borehole-geophysical logs will ensure that data collected by the USGS Water Science Centers will remain available in a readily usable format for support of published reports, future scientific investigations, and data requests from the public.

 

William M. Alley
Chief, Office of Groundwater

 

Distribution:      Senior Staff
                        Water Science Center Directors
                        Regional Groundwater Specialists, NR, SR, CR, WR
                        Water Science Center Groundwater Specialists
                        Chief, Branch of Geophysics, CT
                        Office of Groundwater Borehole Geophysics Advisor