Resistivity tool

Drilling Fluids & Logging

A resistivity tool measures how strongly a rock formation opposes the flow of electric current. Since hydrocarbons are insulators (high resistivity) and formation salt water is conductive (low resistivity), this measurement is the key indicator used to differentiate between water-bearing and oil/gas-bearing zones.

There are two main types: Induction tools (using magnetic fields for non-conductive muds like OBM) and Laterologs (using injected current for conductive muds). Advanced resistivity tools can also provide 360-degree borehole images and measure resistivity at multiple depths of investigation to detect invasion profiles.