Two categories of resistivity logs are: induction and laterolog. The laterolog tools use electrodes to inject a current on the formation and to measures voltages at different points in the tool.

The induction tools use coils and magnetic fields to develop currents in the formation whose intensity is proportional to the conductivity of the formation.

The intensity of these currents is measured on receiver coils in the tool. Halliburton provides offerings of both types.

Nuclear tools measure the interactions between radiation emitted from logging tools and the formation, as well as naturally occurring radiation.

Gamma-Ray and Spectral Gamma-Ray tools measure the naturally occurring radiation. The spectral tools provide Potassium, Uranium and Thorium concentrations helping in the detection of producible zones by distinguishing typical conventional reservoir rocks from those containing clays

Spectral Density and Neutron tools are designed to measure formation porosity and lithology. Spectral Density tools provide measurements of bulk density (ρb) and borehole-compensated photoelectric factor (Pe) through measurements of the attenuation of  gamma-rays from a Cs-137 source. A Neutron tool measures porosity from neutron-nuclei interactions from a Am241Be chemical source. Neutron porosity logs provide total fluid information for use with resistivity logs and/or pulsed neutron logs in determining formation water saturation. Density and Neutron tools are typically run together and can an indication of formation gas saturation, and also run with the Sonic log to provide indications of formation lithology

The GEM™ is an Elemental analysis tool used for evaluations of complex mineralogies and provides elemental contributions contained within the total measured gamma-ray spectrum.  The tool utilizes the same Am241Be source as the Neutron porosity tool and measures the energy level of gamma-rays which are emitted from the various elements once the neutrons are captured by those elements.  The energy level of the gamma-rays identifies and quantifies the elements in the formation.

Sonic, or Acoustic, tools measure the traveltime (Δt) of a compressional, P, wave as it travels through a formation, they can also measure shear, S, velocity, which is useful in understanding rock mechanical properties. In hard-rock sediments, acoustic logs are used to calculate secondary, or vugular, porosity. In complex lithology’s, to measure porosity Sonic logs are run in combination with compensated density and neutron tools.

The latest generation of Sonic tools can measure Sonic Anisotropy, which can be used to determine the orientation of natural fractures. Sonic attributes such as P-wave slowness, fast and slow S-wave travel time, identification of compressive fluids in the pore space, and anisotropy orientation all allow for better 3D seismic analysis.

These tools impose an external magnetic field in the formation and make a measurement that is proportional to the porosity, regardless of lithology.

This allows identification of the free- and bound-fluid volumes and the free-fluid type (gas, oil or water). It also provides an indication of permeability