AU34169 - Conversion of well log data
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This job involved transcription of 1381 9-track tapes containing mostly LIS format data.


      - Tapes shipped as per client transmittals - 1384 (1371 + 1 fm Kestrel; 12 fm PIVIC)
      - Total tapes as per client spreadsheet    - 1370 (Kestrel); 1369+12 (PIVIC) 
      - Total tapes physically received          - 1384 (then 3 returned to Kestrel)
      - Total tapes transcribed                  - 1381
      - Total tapes NOT transcribed              - 0 (apart from 3 returned)


OUTPUT ORGANISATION
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      Data Type      #Input Tapes     Output Media                Comments   
      Well          1381              HDD-USB  


PROCESS
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        - Read tapes, applying data recovery as required, create TAP format file
        - Convert from TAP/LIS format to DLIS; run DLIS verification (.html)
        - Convert from DLIS to LAS; run LAS certification (.log)
        - If not LIS, identify format and handle as appropriate


MEDIA QUALITY
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The tapes were mostly 800bpi and 1600bpi and data recovery techniques were required to be applied.  Despite this, many tapes still exhibited some level of data loss with 281 tapes exhibiting hard errors while reading - even after multiple attempts.


FORMAT ISSUES - TAP
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The raw data read from tape was TIF-encapsulated in a file with ".tap" extension.  Some of these files were subsequently "repaired" as they were found to have bogus End-Of-File marks or rubbish data blocks preceding the good data.  TAP files contain the original tape data including blocking and EOF information - this is effectively a disk version of the original tape content.  LIS data in TAP format is a standard accepted by many well log software programs.


FORMAT ISSUES - DLIS
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These TAP files were then checked for LIS content and 1373 of 1381 were converted to DLIS on disk.  Of the remaining 8:
       - 4 tapes were SEGY format - PE010542, PE010760, PE010808, PE010754
       - 3 tapes appear to be LIS but missing valid LIS headers - PE010789, PE011279, PE011097
       - 1 tape was apparently blank - unable to recover any data - PE011218

In addition, 1 tape was missing LIS headers for the first file, but the subsequent files on tape were converted to DLIS (i.e. one dataset lost) - PE010579.

Of the 1373 DLIS files created, all were verified for content and 311 reported DLIS errors - many of these are associated with the hard errors encountered while reading.  In addition, 523 files reported "empty frame" errors.  These errors appear to be inherent in the data regardless of hard errors.


FORMAT ISSUES - SEGY
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The 4 SEGY files were written to raw SEGY on disk.

Of the 4 SEGY tapes, one was blocked as SEGY (3200 byte block, then 400 bytes, etc.) but the internal data was clearly not SEGY format.  The data on this tape is considered to be useless.


FORMAT ISSUES - LAS
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Where possible, the DLIS files were then converted to LAS files - a total of 927 LAS files created.  The main reason for LAS files to NOT be created was the existence of "empty frame" errors in the DLIS files.  If the first DLIS frame was empty, no LAS would be created.  If subsequent DLIS frames were empty then the LAS would be created but prematurely terminated.

Of the 927 LAS files created, 79 reported errors in structure, although there will be more than these 79 that are incomplete.