Mount Sopris Instruments

QL40-DEN

Dual Density + Caliper

Near and far density measurements transformed into compensated density

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Description

The QL40-DEN measures the density in g/cc of the formation crossed by a borehole.

Density is a typical property of minerals, fluids and rocks. Density measurement is often used in geophysics, petrophysics, sedimentology and geotechnics. The technique requires a 137-Cs or 60-Co radioactive source attached at the bottom of the tool to excite the formation with gamma radiation. In addition the QL40-DEN is implementing a single arm caliper used to record a continuous diameter log and to push the gamma detectors against the borehole wall while measuring the density.

The QL40-DEN is a bottom sub. It can be combined with other logging tools of the QL40 (Quick Link) product line or can be operated as a standalone tool.

Applications

  • Density – porosity estimation
  • Lithology determination
  • Bed thickness
  • Sedimentology - determination of depositional environment, diagenesis and compaction
  • Detection of fractures and cavities
  • Rock mechanical parameters (in combination with sonic logs)

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QL40-DEN — Dual Density + Caliper — Near and far density measurements transformed into compensated density

Technical Specifications

Tool

  • Diameter: 51mm (2.01”)
  • Length: 1.83m (72.24”)
  • Weight: 19.2kg (42.33 lbs)
  • Temp: 0 - 85°C (32 - 185°F)
  • Max. Pressure: 200bar (2900psi)

Sensor

  • Short spaced source detector (SSD): 1.27 cm x 1.27 cm (0.5” x 0.5”) CSl(TI) scintillation crystal 20cm (7.87”) spacing

  • Long spaced source detector (LSD): 3.81 cm x 1.27 cm (1.5” x 0.5”) CSl(TI) scintillation crystal 35cm (13.77”) spacing

Operating Conditions

  • Cable type: Mono, multi-conductor, coax
  • Compatibility: Scout Pro / Opal (Scout / Bbox / Matrix)
  • Digitaldata transmission Telemetry: Variable baudrate telemetry according to cable length/type & surface system
  • Logging speed: 5-6 m/min recommended
  • Centralisation: Decentralized
  • Borehole conditions:
    • Water filled
    • Open hole (quantitative data)
    • cased hole (qualitative data only)
  • Measurement range:
    • Caliper Max : 29.2 cm (11.5”)
    • Caliper Accuracy : 2.54 mm (0.1”)
    • Caliper Resolution : 0.64 mm (0.025”)
    • Density Range : 1 - 4 g/cc (depends on source)
    • Source : 137Cs or 60Co
    • Density Accuracy : 0.1 g/cc (with a 100 mCurie 137Cs)
    • Density Resolution : 0.05 g/cc (with a 100 mCurie 137Cs)

Principle of measurement

The compensated density measurement is accomplished using a radioactive source and a set of two CsI(Th) scintillator crystals coupled to two photomultiplier tubes. The detectors are designed for use with a 137Cs or 60Co sources and are configured to respond to gamma particles having energies from 0.2 to 2 Mev (the Compton energy band). They are shielded so that they only respond to gamma radiation from the side of the tool in contact with the borehole wall. Gamma radiations emanating from the source collide with electrons in the atomic structure of the formation. By a process known as “Compton scattering” the gamma rays pursue their travel with a lower energy and a change of direction. These scattered gamma rays are counted by a Short Spaced Detector (SSD) and a Long Spaced Detector (LSD) providing two different depths of investigation. The number of gamma rays counted is directly proportional to the number of electrons in the formation or in other words to electron density. Electron density is closely related to bulk density. To derive the bulk density of the formation in g/cc the tool is calibrated using two reference jigs of well known bulk density.

Measurements features

  • SSD: in CPS
  • LSD: in CPS
  • SSD density: in g/cc
  • LSD density: in g/cc
  • Compensated density (RHOB): in g/cc
  • Compensation (DRHO): in g/cc
  • Caliper: in mm or inch