Resistivity logging is a fundamental material property and one of the oldest logging techniques. It works by characterizing the rock or sediment in a borehole by measuring electrical resistivity. This represents how strongly the material opposes the flow of electric current. This ability of the rocks to conduct electrical current is scaled in ohm-meters and is the inverse of conductivity. The ability to conduct electric current depends on the volume of water, temperature and salinity of the formation.
Resistivity logging is used for mineral exploration, water well drilling and formation evaluation and is probably the most widely used logging technique after natural gamma logging.
Resistivity measurements are used for:
– Correlation and source rock identification
– Over pressure identification
– Formation water salinity and Hydrocarbon saturation
Geovista manufacture 2 types of resistivity sondes:
1. Normal Resistivity Combination Probe – Includes 16” & 64” Normal resistivity, SP and SPR (this is the traditional sonde used widely in industry)
2. Dual LL3 Focused Resistivity probe - Includes LLD & LLS Focussed Resistivity and SP
A comparison of the measurements acquired by the two sondes is shown below: