The three arm caliper probe provides a single continuous log of borehole diameter as recorded by three mechanically coupled arms in contact with the borehole wall. The caliper is a useful first log to determine the borehole conditions before running more costly probes or those containing radioactive sources. Once opened, the spring-loaded arms respond to borehole diameter variations as the probe is raised up the borehole.
The Elog is the classic water-well combination probe combining shallow, medium and deep penetrating resistivity measurements with self-potential (SP). A low-frequency bi-directional electric current from a source electrode on the probe returns through the formation to the cable armour above an insulated bridle. Potentials due to this current flow are measured on various sense electrodes on the probe with respect to a voltage reference ‘fish’ normally located at the surface. These measurements are converted to apparent formation resistivities within the probe and digitally transmitted to the surface.
The gyroscopic verticality probe acquires borehole inclination/azimuth logs in situations where metal casing or magnetic materials around the borehole prevent use of the standard verticality probe. The 3D-magnetometer version also acquires 3D-magnetic data for location of magnetic ore bodies. Can compute the magnitude and direction of the magnetic field around the probe.