In the oil field, exploration of the subsurface through well logging provides measurements of the characteristics of rock formations and fluids to help identify and evaluate potential reservoirs. Downhole nuclear measurements focus on formation properties such as natural radioactivity, formation density, and hydrogen content, as well as the identification of the elemental and mineralogical composition of the rock through spectroscopy. Accurate nuclear modeling is a fundamental part of nuclear well logging tool development, from concept through design to response characterization. Underlying the accuracy of nuclear modeling is a good knowledge of nuclear cross sections of the elements in the tool, borehole, and subsurface formations. The recent focus on replacing tools based on radio-isotopic sources with those based on D-T neutron generators opens many opportunities for new measurements but highlights the deficiencies of current cross sections. For example, in neutron-induced inelastic and capture gamma ray spectroscopy, major obstacles come from a lack of or inaccuracies in the cross sections of essential materials.
Electro-permanent magnetic weight release mechanism for buoyancy control of an autonomous well-logging tool
