Geovista - Dual Guard Focused Resistivity Probe

Resistivity is a fundamental property of materials and resistivity logging is one of the most mature geophysical logging techniques. The DLL3 probe provides a deep and shallow resistivity measurement at a higher vertical resolution and offers deeper penetration than is possible with a standard ELOG probe. This is achieved by sending a measure current from the drive electrode to the cable armour beyond the isolating bridle. The current is focused by a bucking current which flows from the connected guard electrode pairs. The potential of these guard electrode pairs is kept equal to the drive electrode, this turns the sonde into an equipotential surface and forces the measure current to flow out perpendicular to the sonde orientation.

Resistivity logging is a staple in mineral exploration, water well drilling, formation evaluation, and many other applications. After natural gamma logging, it is probably the most widely used logging technique.