Borehole Wire‐line Logging for Uranium - 2009

Uranium (Nuclear Minerals) / Exploration, Mining, Marketing, & Acquisitions

Skidmore presented a discussion on borehole logging during a SMEDG Symposium 11 in September, 2009. This is the PDF he used for his presentation.

Why use borehole logging?

• Cost effective
• Instantaneous results
• Very accurate depth control
• Excellent resolution of narrow intervals (typically 1 cm compared to ~1 m with physical sampling)
• Measures larger sample volume compared to collection of physical sample
• Measures a wide range of petro-physical properties

Wire‐line Tools – Uranium Grade

• Total Gamma

– Indirect measurement of uranium (²¹⁴Bi & ²¹⁴Pb)
– Cheap and reliable equipment
– Measures all radio‐nucleotides (Sum of K+Th+U+…)

• Spectral Gamma

– Measures the energy spectrum of gamma radiation and to a degree can discern between different radio‐nucleotides
– Only cryogenic high‐purity germanium systems can potentially discern peaks directly associated with uranium (e.g. 1.001MeV of Protactinium ²³⁴Pa)

• PFN (Prompt Fission Neutron)

– Direct measure of ²³⁵U
– Provides spontaneous measure of disequilibrium
– Expensive, complex, high maintenance system
– Requires specialist radiation licensing
– Limited availability
– Very slow logging speed (~0.5m/min)
– Restricted access to appropriate calibration facilities

Wire‐line Tools ‐ Geology

• SP & Resistivity

– Commonly used in historic logs with variable success discerning permeable strata
– Poor results with modern digital systems due to drift and with modern saline drilling mud, which results in insufficient resistivity contrast

• Neutron Porosity

– Generally excellent at determining variations in porosity
– Uses sealed neutron source (AmBe) requiring licensed operators and radioactive substance management

• Induction (single or dual)

– Good results in dry holes and saline conditions
– Be careful of sulphides as give very high conductivities

• Focused Resistivity (Guard/ Laterolog)

– Very useful at picking lithological boundaries
– Only useable below the water table
– Safety considerations as requires long bridle and can expose operator to potential electrocution

• Magnetic Susceptibility

Wire‐line Tools – Others

• Caliper

– Borehole diameter (critical factor for grade determination)

• Deviation

– Borehole orientation

• Optical

– Expensive additional cost (typically ~$5 per meter)
– Geology, structure, well casing integrity etc.


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