The QL40-DEN Compensated Density & Caliper probe is a versatile wireline tool that can be used in a wide variety of logging applications. Measurements include SSD (short-spaced density), LSD (long-spaced density), Compensated density (dual density), and Caliper. The tool section is designed for operation in 2 to 12 inch (5 – 30 cm) boreholes.

This dual detector, high resolution density tool is fully characterized, producing accurate near and far density measurements transformed into compensated density by use of stand-off / compensation algorithms. These algorithms produce effective data even when borehole rugosity and fractures adversely affect accuracy of uncompensated logs.

The QL40-DEN tool is stackable within the Quick Link (QL) product line or it can be run as a standalone tool.


  • Quantitative In-situ Density
  • Petrophysical Properties
  • Coal Quality and Delineation
  • Density Porosity
  • Caliper Borehole Volume

Operating Conditions

Borehole Fluid
[X] Water
[X] Mud
[X] Dry

[X] Uncased
[_] PVC Borehole
[_] Steel

[_] Required
[X] Tool is De-Centralized

Features & Benefits

  • Real-time Quantitative Density
  • Improved thin bed resolution
  • Advanced compensation algorithms produce accurate density data even when borehole rugosity and fractures are obstacles
  • Easy to calibrate with Nylon and Aluminum calibration blocks.
  • Cesium-137 or Cobalt-60 source
  • Strong and reliable caliper, driven by gas-charged piston-type actuator
  • Operates on any standard wireline (Mono, 4, 7 conductor, or Coax)
  • Can be combined with other logging tools of the QL product line or operated as a standalone tool.

Example QL40-DEN Density through Coal Seam

Specifications – Metric/English

Specification Metric Imperial
Diameter 50.8 mm 2″
Length 1.85 m 73″
Weight 19.2 Kg 42 lbs.
Max. Temp. 85ºC 185ºF
Max. Pressure 206 bar 3000 psi


Short Spaced Source Detector (SSD): 20 cm (7.87”)
Long Spaced Source Detector (LSD): 35 cm (13.77”)
Density Range: 1 – 4 g/cc (depends on source)
Source: 100 – 250 mCurie Cs-137 or Co-60
Density Accuracy: 0.1 g/cc (100 mC Cs-137)
Density Resolution: 0.05 g/cc (100 mC Cs-137)

Caliper Maximum: 30 cm (12”)
Caliper Accuracy: 2.54 mm (0.1”)
Caliper Resolution: 0.64 mm (0.025”)

QL Stack Possibilities

  • QL40DEN + QL40GR (Gamma): Exploration, Petrophysics Properties
  • QL40DEN + QL40GR (Gamma) + QL40DEV (Deviation) : Exploration, Borehole Deviation
  • QL40DEN + QL4SGR (Spectral Gamma) + QL40ELOG (Resistivity): The ‘Coal Suite’ tool set, Quantitative Analysis, Lithology, Porosity Estimates


Data Sheet
User Guide

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