Stringent legislation on the transport and handling of radioactive materials increasingly prevents use of conventional density logging probes. The small-source density probe provides calibrated and borehole-compensated density logs at sensible logging speeds using a very low activity 60Co gamma source that may not require a radiation licence in certain territories.
Principle of Measurement:
The probe contains a detachable collimated gamma source and two high-sensitivity scintillation gamma detectors. The detectors are protected against direct radiation from the source or via the borehole by extensive heavy- metal shielding. The active windows of source and detector are maintained in contact with the borehole walls by a motorised caliper arm. The detected backscattered gamma radiation depends on the formation density. The probe includes a third gamma detector mounted remotely from the source for ‘stripping’ natural background radiation.