A History of Nuclear Spectroscopy in Well Logging

This paper provides a history of nuclear spectroscopy in well logging from its beginnings in 1939 up until the present day. After the invention and implementation of gamma ray logging, this paper traces the technological development of the pulsed-neutron capture (sigma) log, the spectral gamma ray log, the carbon-oxygen log, tracer identification logs, small-diameter reservoir characterization tools, and finally the geochemical log. The key to the science of nuclear spectroscopy has been the detection of gamma rays, their energies, and the identity of their parent atomic nuclei. From this, the properties of the formation can be better understood. There have been many advances in technology that have led to the current state of nuclear spectroscopy tools. The most notable has been the ability to detect the presence of a gamma ray. After this came numerous advances in scintillator crystal detector technology, the pulsed-neutron generator, the energy digitization of gamma ray pulses, fast-timing electronics, and powerful computers. These advances have made possible the complex, gamma ray-centric logging tools that we have today that have helped petroleum engineers in the energy industry locate and produce hydrocarbon, kerogen, and natural gas reservoirs for the benefit of each individual in the world. This paper discusses the rich history of these historic developments.