Geochemical Spectroscopy Tool

Enables quantification of mineralogy, lithology, and organic carbon for improved saturations and reservoir characterization


  • Mineralogical quantification, including clay types
  • Detailed lithological analysis
  • Matrix density and matrix-corrected porosity
  • Enhanced porosity and oil saturation calculation
  • Total organic carbon (TOC) determination
  • Formation sigma

Features and Benefits

  • The geochemical spectroscopy instrument (GSI) functions as an integrated answer product that generates mineralogy and detailed lithology.
  • The service combines 15 elements: 12 from the GSI (Al, Ca,C, Cl, Gd, H, Fe, Mg, O, Si, S, Ti) with three from spectral gamma ray (K, Th, and U) for complete mineralogy determination.
  • Diffusion-corrected sigma aids in formation evaluation and reservoir characterization.
  • Real-time lithology and elemental concentrations are available at the wellsite, which enables time-sensitive decision-making.
  • A 14 MeV pulsed-neutron generator provides for comprehensive inelastic and capture gamma ray detection.
  • No chemical radioactive source is required, which enhances safety in the case of a fishing incident or lost-in-hole event.
  • The lanthanum bromide (LaBr3) detector exhibits enhanced energy resolution with fast emission and temperature linearity characteristics.
  • The instrument can be deployed using advanced Assure conveyance techniques.
  • Memory capabilities enable cost-effective horizontal logging.

Tool Description

The geochemical spectroscopy instrument (GSI) uses a pulsed-neutron generator to induce inelastic and capture gamma rays. Measuring the gamma rays enables identifying key formation elements. The final lithological and mineralogical interpretation is guided by these elemental concentrations, as well as by the measurement of intrinsic sigma. The interpretation software processes the input, analyzes the lithology, and improves the identification of matrix properties for use in further reservoir characterization.

The tool is offered solely as a limited release, with no guarantees of availability or deployment in all locations, for the purposes of research, development, and experimentation. Weatherford does not warrant or represent that the tool will provide all desired functionality or will meet the requirements of a particular customer application.




Vertical resolution

18 in. (457 mm)

DOI inelastic events

8.5 in. (216 mm)

DOI capture events

10.5 in. (267 mm)

Measurement energy range

0.6 to 9 MeV

Energy windows


Capture elements

Ca, Cl, Fe, Gd, H, Mg, S, Si, Ti

Inelastic elements

Al, C, Ca, Fe, Mg, O, Si

All elements (GSI + SGR)

Al, C, Ca, Cl, Fe, Gd, H, K, Mg, O, S, Si, Th, Ti, U



Tool diameter

3.25 in. (83 mm)

Tool length

11.5 ft (3.5 m)

Temperature rating

302°F (150°C)

Pressure rating

15,000 psi (103 MPa)

Maximum hole size

24 in. (610 mm)

Minimum hole size

3.75 in. (95 mm)

Neutron source

14 MeV pulsed-neutron generator

Answer Products

Field deliverables

Elemental concentrations including Al, Ca, C, Fe, Gd, K*, Mg, S, Si, Th*, Ti, U*

Formation sigma

Dominant lithology

Qualitative elements (H, Cl, O)

Standard interpretation

Formation mineralogy (in dry weights and volumes)

Detailed lithology (lithofacies)

Matrix density

Clay types and volumes

Organic carbon

Matrix-corrected porosity

Advanced interpretation


TOC/kerogen volume

Integrated answer products

*Th, U, and K come from the spectral gamma ray.

Geochemical Spectroscopy Instrument

The geochemical spectroscopy instrument is used in a Weatherford service that measures 15 elements to provide real-time lithology and elemental concentrations. The instrument can be deployed using advanced Assure conveyance techniques.

Reach out to optimize reservoir performance

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