Accelerators have been integral to subsurface probing for decades. Tools with deuterium-tritium (D-T) generators and scintillators utilizing gamma rays from thermal neutron capture, inelastic scattering, and activation are routine in cased-hole logging tools for reservoir and well monitoring to locate and quantify remaining hydrocarbons prior to initiating secondary or tertiary production. X-ray and neutron generators field-tested to, respectively, replace 137Cs and americium-beryllium (Am-Be) source tools that measure two bulk parameters, formation density and neutron porosity critical for initial characterization of formations, have yielded mixed results. D-T generator-based spectroscopy tools with advanced scintillators that can record both inelastic and capture n-gamma spectra, faster and with much better energy resolution, to provide a more complete mineralogy appear poised to replace Am-Be–based mineralogy tools. In view of their ability to measure both bulk and spectral parameters, accelerator-based nuclear methods appear attractive to extract additional geological information needed to transition to a low-carbon energy future.
The paper discusses the current state of application of accelerator-based subsurface probing techniques, notes their potential for nonpetroleum applications, and concludes by briefly exploring technology advances that could significantly advance the state of the art.