POSC PWLS V2.0 Reference Data Release
POSC Practical Well Log Standards
A Standard for Well Log Curve Classification

Release History
Version 2.030-Sep-2003PWLS Revised and Expanded Results
General release.
Version 2.a 01-Jul-2003 PWLS Revised and Expanded Results 
Review release.

PWLS Revised and Expanded

  • Briefly, PWLS Version 2 is both a revision and expansion to Version 1.0.
    • Version 2 reflects the resolution of the dual classification issue from Version 1.0.
    • Version 2 is presented in a more structured way that identifies clearly service company provided information versus industry-oriented, PWLS-provided information.
    • Version 2 includes additional service company tool/channel/curve data and pseudo service company data defining PWLS curve mnemonics for oil company calculated interpreted and composited curves.
    • There are no substantive content changes between Versions 1.0 and 2 for acquisition curves. Version 2 includes POSC defined standard mnemonics for joined (composite) and interpreted (processed) curve classes.

Quick Access to the PWLS V2 Specifications

Project Information

Why Do This?

The formation of the Practical Well Log Standards (PWLS) was motivated by several Well Log management business issues. Users have difficulty finding the important Well Log data, because there are so many types of curves. Names for both individual curves and collections of curves are complex and are changing at an ever increasing rate. The lack of consistency over time is confusing for experts and generalists alike. Until now, there has been no recognized central source for Well Log naming standards. POSC organized the PWLS project to establish and promulgate such standards for use throughout the industry.

  • Most of the business value of Well Log data is concentrated in a relatively small number of types of curves. There are on the order of 50,000 visible acquisition curve types of which about 1,000 deliver the majority of the value. 
  • The goal is to remove the mystery surrounding curve names caused by the current proprietary and esoteric naming systems.


Tool Names

Tool names for acquisition data will maintain their full technical / marketing names for continuity. Generic service class names are defined to be understandable to all and to remain consistent over time. Specific tool string names will be created by concatenating component tool names. [?]

Consider these Tool Type examples:

Tool Types  Tool Type Descriptions
ARIN Array Induction Resistivity
ARLL Array Laterolog Resistivity
AUX Auxiliary
DEN Density
DEN.NEU Density, Neuron
GR Gamma Ray
NMR Nuclear Magnetic Resonance
SP Spontaneous Potential
Curve Names

For curve names, the service company mnemonic is retained as the fundamental curve identification. Generic, cross-vendor classifications are defined to increase understandability and for use in conducting processing activities. In Version 2, the curve classes are a proper subset of an broadly defined hierarchy of Property Types. In addition, each Property Type used to express a curve class is defined with a set of characterizing attributes: object in which measurement is made (usually formation), special measuring technique, basic property being measured, property modifiers, and mathematical function applied to formulate the result.  

Here are the same examples:

Baker Atlas Curve Mnemonics Halliburton Curve Mnemonics Schlumberger Curve Mnemonics Property Types Curve Class Attributes
ATT1, ATT2, ... LSA1, LSA2, .. Acoustic_Amplitude Technique=Acoustic, Property=Amplitude
    ISSA, STIK, ... Sonic_Data_Density Technique=Acoustic, Property=Data_Density
CAL, CALX, ... HSI, SDK2, ... LCAL, RLCA, ... Caliper Property=Caliper
    DCAL Differential_Caliper Prosperity=Caliper, Modifier=Differential
M2C1, M2C2, ...   AIBC, AIFC, ... Induction_Array_Conductivity Property=Conductivity, Modifier=(Induction, Array)
CLLD, CTBR   CLLD Deep_Laterolog_Conductivity Property=Conductivity, Modifier=(Deep, Laterolog)
BDCM, BDCX, ... RHOB, BD2, ... HDEB, HRHL, ... Bulk_Density Property=Density


The V2 Release

The goal for V2 is to publish an effect set of specifications that effectively supports the main purpose of PWLS, i.e. to support the classification of well log curves that are commonly used by oil companies and to use this classification as a tool to support general queries over large populations of curves. 

PWLS V2 carries forward the results published in V1 classifying the following categories of logging tools from the participating service companies:

  • Nuclear Tools
  • Resistivity Tools
  • Acoustic Tools
  • Electromagnetic Propagation Tools
  • Magnetic Resonance Tools

In addition, V2 includes recommended curve mnemonics for oil company produced interpreted and composite curves. V2 also includes the structure to enable the application of classification to high-level logging services, to computational processes, and to log header parameter specifications.

PWLS V2 reflects the resolution of the dual classification approach adopted in V1, eliminating the inherent ambiguity in that approach. This was accomplished with the active encouragement and support of the PWLS Special Interest Group, formed in 2002, and through the cooperation of the participating service and software companies. The key concept used to achieve this resolution was that the characteristics of a class are not and should not be interpreted from the name of the class.


The technical work to formulate PWLS V2 was performed by the POSC staff with support from participating organizations for consultation and, above all, for company specific data. As mentioned, the encouragement to achieve an effective and useful PWLS standard from the Special Interest Group was essential.

Future Planning

In parallel with the publication of PWLS V2, there is active dialogue in progress with service and software vendors to ensure a common understanding, to encourage and assist in the deployment of PWLS V2 in products and in oil company data management procedures, and to ensure that service companies maintain a complete and current flow of new and updated information to POSC. 

The PWLS Special Interest Group is the formal user group for the PWLS standard. As such, it will continue to highlight requirements and needs that will be addressed by POSC and will influence future releases of the standard.

POSC is prepared to contribute and/or to organize resources, as necessary, to expand the scope of PWLS classified well log curves. Some service companies are comfortable taking the lead to select the high and medium value curves and to determine the proper classification, i.e. Property Type and associated Curve Class Attribute Values. In other cases, POSC will work with service companies and oil companies to form expert groups that can perform this task. If there are general technical issues that need consultation with a full cross-section of service company and/or oil company support experts, then POSC will announce and convene a technical working meeting for that purpose.  

Another process undertaken by POSC is to consult with groups (inside or outside the POSC community) that manage standards related to well log curve data to ensure that the maximal beneficial value of using the PWLS standards is understood, enabled, and encouraged.

Among the candidate subjects previously deemed worthy of future consideration are:

  • Classify additional high and medium value acquisition curves currently in use
  • Classify high and medium value acquisition curves for tools previously in use
  • Classify historical acquisition tools
  • Classify dipmeter/image tools
  • Classify formation pressure tools
  • Classify core data
  • Classify deviation data (survey and interpolated)
  • Classify mud log data
  • Classify VSP data

Comments about this work may be directed to Jana Schey.

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Last modified: September 25, 2003
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