Logging

The new suite of slimline, stackable tools allows customizing the tool stacks for specific applications, therefore improving downhole logging data quality since multi-parameter measurements are gathered in a single run, in turn leading to reduced logging time. Each tool is equipped with its own telemetry board, power supply element and A/D converter, so they can also be operated as stand-alone probes if necessary.

The following logging tools are available to scientists at Leicester (subject to availability), but are provided by the University of Montpellier (Laboratoire de Géosciences-Montpellier, France), as part of the EPC under ESO. Learn more about the tools.

• ANTARES
• Mount Sopris Instrument Company, Inc.
• GeoVista
• Advanced Logic Technology (ALT)

Spectral natural gamma probes (ASGR and QL40 GAM)

Primarily a lithological tool, formation gamma rays are detected and counted by a either a Sodium Iodide or Bismuth Germanate scintillation crystal which converts incident rays into light pulses. Energies of the incoming rays are proportional to the brightness of the light pulse and thus determine the size of the electrical pulse produced by the photomultiplier. This allows identification of individual elements that emit gamma rays (e.g., potassium, uranium, and thorium), which can then be interpreted, i.e. for the identification of specific clay types, like kaolinite or illite. Since natural gamma emission is partially volume dependent the logs can also be used for identification of fractures, bedding planes, facies changes, for (groundwater) exploration purposes and lithology characterization.

Induction conductivity probe (DIL45) and Dual Laterolog tool (DLL5)

Tools that measure electrical conductivity of the surrounding geological formation. The output of these tools comprise two logs: induction electrical conductivity of medium investigation depth (ILM; 0.57 m) and induction electrical conductivity of deeper investigation depth (ILD; 0.83 m). These logs are used in the identification and qualification of ores, as an indicator for hydrocarbons as well as an indicator of permeable zones (fractures) and porosity of the surrounding rocks.

Magnetic susceptibility probe (EM51)

Magnetic susceptibility is the degree of magnetisation of a mineral in response to a magnetic field. This tool measures magnetic susceptibility in a wide range of formations for use as a lithological indicator (by way of mineral identification), and for stratigraphic correlation. It can also be used in the identification of ores for exploration and the economic evaluation of deposits.

Acoustic borehole televiewer (AB140)

Acoustic imaging operates by pulsing acoustic energy using a rotating transducer and detecting two-way travel times to the borehole wall. This produces a 360 degree image of the borehole with the slimline tool achieving millimeter-scale, high-resolution (72 parts per thousand [ppt]) images. Images can be used for the detection and evaluation of fractures, breakout analysis, lithology characterization, the detection of thin beds and determination of borehole deformation (stress field analysis).

Optical borehole televiewer (OB140)

Operating similarly to an endoscope, the OB140 produces millimeter-scale, high-resolution image of the borehole wall. This tool is operated where seawater is used instead of drilling mud, such as Expedition 325: Great Barrier Reef.

Full waveform sonic probe (2PSA)

Sonic tools are those that measure compressional wave velocities of the formation. Sonic logs are widely used to provide porosity, permeability and geomechanical properties of rocks, including Elastic moduli, Poisson’s ratio, shear modulus and bulk modulus and compressibility. In addition, sonic logs can be used for the identification of lithologies and fractures as well as the hydraulic characterization of the latter.

Caliper tool (2PCA-1000)

Continuously records borehole diameter of the by means of three mechanically coupled arms in contact with the borehole wall. The logs can be used for the localisation of fractures and cavities and the evaluation of rock integrity, but can also provide information on the quality of other tools’ data. This is where distance to the borehole wall affects signal quality such as in natural gamma tools.

Hydrogeological probes (IDRONAUT and QL40 Ocean)

Both tools measure hydrogeological properties of the borehole fluid, including borehole fluid pressure and temperature, electrical conductivity, pH and Eh. Produced data informs on sea and fresh water properties, the location of aquifers and logging of geothermal gradients.

Spinner flowmeter (QL40 SFM)

Designed to measure impeller rotation caused by fluid flow in the borehole. Logs can be used for the identification of hydrostratigraphic units and the provision of pumping flow profiles in screened or perforated cased holes.

Fluid temperature and conductivity probe (QL40 FTC)

Provides temperature and fluid conductivity measurements in the borehole. Logs can be used for salt-water intrusion studies, the identification of fluid flow in the hole, for geothermal gradient logging and water table location identification.