Multi-functional Borehole Logging Tool Based on Pulsed-neutron Generator Technology

摘要

Heathgate has implemented advanced prompt fission neutron (APFN~+) technology for comprehensive borehole logging. It is ideally suited for the exploration of sedimentary-hosted uranium deposits as well as the characterisation of in situ recovery (ISR) wellfields. The technology can also be applied to metal prospects in various geological formations.APFN~+ combines pulsed-neutron generator technology with multi-scaling neutron detection by six ~3He counters at several positions and energy ranges as well as y-ray spectroscopy by the use of a high-performance CeBr_3 scintillator. A magnetic/gravity sensor system has been integrated to measure borehole inclination.The main logging functions of the APFN~+ tool include: ? accurate uranium grade (PFN method with important in-tool corrections for systematic influences)- abundance of U and Th progenies as well ~(40)K based on natural y-ray spectroscopy (deduced U/Ra disequilibrium)- geophysical parameters including hydrogen index, density, macroscopic neutron (absorption) cross-section, neutron scattering strength and clay indicator- deduced (free-fluid) porosity and estimated (hydraulic) permeability- high-resolution (quantitative) lithological profiling following Shepard's nomenclature (extended)- borehole diameter (deduced from intensity of thermal neutron capture by hydrogen)- abundance of main minerals (from spectroscopy of neutron-induced y-rays in multiscaling mode).The diversity of functions integrated in one tool enables a highly efficient logging, potentially replacing the requirement to use several conventional logging tools entirely. The tool functions were calibrated by the combination of extensive computer simulations (software MCNP6) based on detailed lithological modeling with new dedicated calibration pits and reference boreholes installed by Heathgate.