Compensated Neutron Log (CNL)

The Compensated Neutron Log tool contains a neutron emitting source, which produces fast neutrons that bombard the formation. The emitted neutrons are slowed (thermalized) by collision mainly with hydrogen nuclei in the formation. Some of the slowed neutrons return to the tool where they are counted by two He3 detectors, spaced at different distances from the source. The dual outputs supply compensation for rugose borehole conditions.

CNL measures the formation porosity based on the presence of hydrogen in the formation. The tool comprises a radioactive source of either Cf or AmBe isotopes and a set of two detectors.

CNL – Key features
  • It is modeled for both Am-241Be and Cf-252 sources.
  • It is compensated for:
    - borehole conditions
    - correct for casing
    - cement
  • Can be run in combination with other UW tools, or by itself.
  • The short tool length eases rig up.
Benefits of CNL

The CNL can be used to determine formation porosity and highlights the presence of gas when run in combination with other tools. It is compensated for various environmental conditions, and can be run in a cased hole environment to determine porosity through casing. The CNL incorporates a bowspring decentralizer.

The bowspring decentralizer helps to ensure that both it and the LDT are against the borehole wall, facilitating consistent high quality data.

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