LAS Digital Well Log Curves

Specification Guidelines

Well Integrity

  • The entire wellbore system is validated to ensure accuracy of the well information provided such as API/UWI number, orginal operator, well name and well number. The following information is provided with qualifiers: locations, elevations, depths, dates. An H-diagram of the well system is provided for each licensed LAS
  • Image logs will be checked for quality and coverage before  digitizing
  • Digital data will be read, loaded and processed using QC tools

Sonic

  • Typical sonic curves processed and provided 

Curve Type Range
Delta DT, DTL...

Data Capture

  • An LAS file created from original digital data recorded at the well head (“truck data”), or digitized from images, that typically includes as a minimum and where available, the following curves: gamma ray, spontaneous potential, caliper, resistivity (shallow, medium and deep), sonic and density (bulk, correction, and neutron/density porosity, PE). In addition operator reported formation tops will be provided where included in the original digital data
  • Additional logs such as micro logs, dipmeter and other tools, are considered non-standard but may be offered upon request for an additional charge
  • Mud logs (lithology log, strip log, sample log) are available separately as LAS files. See your account manager for details

FDL/CNL 

  • The following curve types are included, where available
Curve Type Example Comments
Bulk Density RHOB, RHBB... Take regardless of log scale
Density Correction DRHO, CORR, DRBB...
Neutron Porosity NPHI, NPOR, CNC, CNF...
Density Porosity DPHI... Take regardless of log scale

Resistivity

  • Where available three curves from a resistivity log will be processed, typically "shallow, medium, and deep resistivity"
Curve Type Range Example Comments
Shallow 10", 20" ASN, AT10, ASFL
Medium 30" ILM, AT30
Deep 60", 90" ILD, AT90 60" of most continuous
Deep (lateral) 8', 18' LAT Digitize all lateral curves

GR, Caliper, SP

  • One each of shared curves in priority as shown available
Curve Type Digitizing Priority #
Most Continuous Res FDC / CNL Sonic
Gamma Ray "GR" 1 4 2 3 1- Digitize the most continuous curve. 2- Infill missing data from next priority log.
Caliper "CALI" 1 4 2 3 Same as above
Spontaneous Potential SP 1 2 4 3 Same as above
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Data Processing

1. Data processed from images:

  • Data values below first reading will be removed during digitizing 
  • Data values in casing will be removed during digitizing , except radioactive curves: (GR, NEUT, NPOR, SIGMA, ect)
  • -999.25 will be inserted for all removed data values
  • Negative values on resistivity will be set at .0004
  • Negative values on GR will be clipped to 0
  • Negative values on DT will be clipped to 0
  • Curves with the same curve name/description will be merged into one continuous curve covering the entire depth available, and curves with different names (eg. AIT 90, AOI 90) will not be merged
  • In case of overlapping runs, shallower runs first reading will be merged to subsequent  deeper runs 
  • All processed curves will retain the original logging contractor mnemonics
  • Header information will be captured for the last run
  • All LAS are subject to a rigorous quality control process to provide both complete curve coverage and a match between the digits and the image
  • With direct correlation, curves such as DPHI and RHOB, and resistivity and conductivity, are overlaid to ensure acccurate digitizing

2. Data processed from digital data:

  • Curves with the same curve name/description will be spliced into one continues curve covering the entire logged depth available
  • In case of overlapping runs a mid point between the logging runs will be used to splice the curves
  • All processed curves will retain the original logging contractor mnemonics
  • Header data will be preserved, including operator formation tops where available
  • Minimal processing of the curve data is applied to preserve as much original data as possible 
  • Multiple data files for a single well will be merged into a single LAS file for easier data handling
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Final Data Output

  • LAS file will be output in LAS version 2.0
  • All standard resolution LAS data will be output at depth increments of 0.5 ft for imperial and 0.1 m for metric
  • TVD curve data, as available may be added as a separate file for an additional charge 
  • High resolution curve data, identified as sampled at less than .1m, may be offered as a separate file where available for an additional charge
  • Log header parameters and information will be provided in the LAS file for the last run available
  • Data delivery is available via R360, LOG-LINE PLus!, FTP, or CD 
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