Sidewall Density, Density/Guard and Iron-ore Density
The sidewall density gamma probe uses dual shielded detectors to provide a borehole- compensated density measurement with good bed-boundary resolution. The sidewall-density/ guard probe offers an additional LL3 focussed electrical measurement with good vertical resolution and depth of investigation.
The iron-ore density probe includes extra collimation, different source-detector spacings and a higher activity source to extend the density range to 5g/cc for iron-ore logging.
Principle of Measurement:
The probes contain a detachable 137Cs gamma source and two scintillation gamma detectors. The active windows of the source and detectors are maintained in contact with the borehole wall by a motorised caliper arm. Gamma radiation back-scattered by the formation (Compton effect) reaches the detectors where the relative count rates provide a measure of formation density.