Environmental corrections for a neutron-induced gamma-ray spectroscopy logging system in an air-filled borehole

When a nuclear explosive is tested underground, rock in the immediate vicinity of the explosion is heated to very high temperatures. If any of that rock contains carbonates (dolomite or calcite), these are dissociated and the carbon may combine with oxygen to form carbon dioxide, thereby increasing the hazard of a delayed leak. The authors are trying to adapt a commercial neutron-induced gamma-ray spectroscopy log to estimate carbonate content in emplacement (2-4-m diameter) boreholes at the Nevada Test Site. Tests were conducted and showed that the log is sensitive not only to carbonate content but also to the water content of the formation as well as the gap between the logging sonde and the wall of the borehole. Tests in boreholes have shown good qualitative agreement with the trends in the sample data but generally indicated somewhat higher equivalent CO₂ content. It appears that the corrections developed in the laboratory may result in an overcorrection. Moreover, other minerals present in the field may decrease the accuracy of the measurement