LAS+ Digital Well Log Processing

The LAS+ log curve set provides the best open hole curve data available for a given well, depth shifted geologically valid curve data that has been edited to remove sections of data adversely affected by drilling or logging (e.g. tool failures, computer glitches, tool pulls, logging drum magnetization). Petrophysicists, Geologists and Geophysicists can work confidently with LAS+ processed curve data that has been quality controlled by our specialists, who have strong backgrounds in geoscience, well logging, and data management.

Well Integrity Validation

The entire wellbore system is validated to ensure accuracy of the well information provided such as API/UWI number, original operator, well name and well number. The following is provided with the qualifiers: locations, elevations, depths, dates. An H-diagram of the well system is provided for each licensed LAS+.

Data Capture

A standard LAS+ curve suite will consist of all available gamma ray, spontaneous potential, caliper, resistivity, conductivity, sonic, density, density correction, neutron, tension and rate of penetration curves.

• Digitized data will be quality controlled against the largest scale hard copy prints
• All missing curves from standard raw LAS will be digitized and included
• All poor quality or incomplete curves will be replaced with the best curves available
• Curve units of measure will be verified against hard copy prints
• Log header parameters and information will be captured and provided in the LAS+ file header

Data Processing

• Data values below first reading will be removed
• Data values in casing will be removed, except the radioactive log curves (GR, NEUT, NPOR, SIGMA, etc.)
• The value -99.25 will be inserted for all removed data values
• All curves will be depth adjusted to the base log, usually a resistivity log, the most common log run top to bottom
• SP mechanical shifts will be removed along with SP drift, and the shale baseline will be adjusted to 0 MV.
• SP will not be flipped unless it is necessary to correct for a digitizing error, only reversing SPWS if it has positive deflection from top to bottom
• CALI will be calculated from DCAL if there is only a DCAL in the log
• A conductivity curve will be calculated from the deep resistivity curve
• Bulk density will be calculated from density porosity using the appropriate matrix and fluid density values, if only density porosity curve is available in the log 
• Where resistivity curves are presented on a log print linearly, the digitized CILD will be reciprocated and the resultant curve will be named CONDWS
• Where the ILD curve values are less than roughly 1 OHMM, the curve values will be replaced with the ILDC values. The resultant curve will be named DREWS
• Original curve mnemonics will be modified to differentiate between the same curves from different logging tool. For example: A Gamma Ray (GR) from Density Log would be named GRD, from the LWD log GRWD if the Gamma Ray doesn't have a mnemonic in the log, or from the SONIC log GRS.
• In the case of overlapping runs, shallower runs at first reading will be merged to subsequent deeper runs
• Processed curves will retain the original logging contractor mnemonics with appended "ED" suffix

LAS+ Curves (WS) - Generic Mnemonics

Using the edited curves, bearing the original logging contractor mnemonics with  the “ED” suffix, key curve types are identified, merged if necessary and given generic well log curve mnemonics with a “WS” suffix to ease identification. Like  curves from multiple run/logs are merged to provide a single curve with maximum  depth coverage. For example, a GRWDED covering the shallower portion of a well  would be merged with a GRDED covering the deeper portion of the well. The resultant curve would be called GRWS. Key curve types from the “ED” curves are  duplicated  and  renamed with  generic  mnemonic. The curve descriptions are added to each curve under the Curve Information section in the LAS+ header.

Listed below are the 17 generic WS mnemonics used and associated units: 

* indicates type of Formation Matrix, either Sandstone (SS), Limestone (LS) or Dolomite (DL)

The standardized  TGS generic WS mnemonics can simplify the workstation environment by allowing the interpreter to use one template, minimizing the complexity associated with multiple logging contractors' mnemonics. 

Final Data Output

• LAS+ processed files ("ED" & "WS") will be output in LAS version 2.0
• LAS+ and raw curves will be output to separate LAS 2.0 files
• Raw and Edited curves will be preserved in original Imperial or Metric units
• Log header parameters and information will be provided in the LAS+ file header
• Data delivery is available via tgsR360.com, FTP, or CD

 TGS has the largest library of immediately available processed well logs in the industry, workstation-ready for correlation, mapping, petrophysical evaluation, and complex integrated analysis.