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Compensated Neutron

The dual neutron module provides an environmentally compensated porosity log in mud-filled open holes. The tool design has been optimised to provide good performance at acceptable logging speeds while still using a relatively small 92GBq 241Am-Be source. It is combinable with the litho-density, dual induction/ dual laterolog and sonic tools to provide the standard ‘quad-combo’ measurements in a single run.

Principle of Measurement:

The dual neutron measurement uses two 3He proportional detectors and a side-door-entry sealed neutron source. Fast neutrons emitted by the source are scattered and slowed down by light elements (principally hydrogen) in the formation. The ratio of the neutron flux reaching the detectors depends on the formation hydrogen index/formation porosity. Neutron porosity measurements are affected by the borehole environment. These effects are compensated in software by algorithms calculated by Monte Carlo modelling and benchmarked to standards at the Callisto facility in Leicestershire, UK. Slim Compensated Neutron Module


  • Well characterised tool response based on computer calculations for limestone, sandstone and dolomite.
  • Fully digital telemetry combines with density, induction and other logging probes
  • Low-activity source requirements for safe handling and cost reduction
  • High-resolution measurement.
  • Maximum data sampling rate is 1cm (0.4”).


  • Porosity (phi)
  • Ratio long/short (NRAT)
  • Raw long and short-spacing counts


  • Porosity evaluation
  • Lithology identification (in conjunction with other logs)
  • Detection of gas or light hydrocarbons
  • Correlation between logs


Diameter: 63mm (2.5”)
Length: 2.07m (81”)
Weight: 27kg (59lb)
Max. temperature: 125°C
Max. pressure: 86MPa (12,500psi)
Porosity range: -15% to +60% limestone

Operating Conditions

Borehole type: 4” to 12” mud-filled open or cased boreholes

Sales Information

I003942 Dual neutron probe
I013962 92 GBq 241Am-Be source
I004124 Source holder
I004122 Source transport pig
I004123 Source handling tool set
I004137 Field check jig
I004132 Bow spring

Download Compensated Neutron sheet


...Practical Innovation with Global Service & Support...

Robertson Geologging Ltd., 2017

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