2018 Volume 71 Pages 148-160
Muography, a density tomography technique using cosmic-ray muons, is widely used to visualize the internal structure of large objects, such as pyramids or volcanos. However, because large muon detectors are used in existing muography technology, the development of a smaller logging tool is required for muography in boreholes to visualize underground structures. We developed a muon density logging tool that can be installed in a borehole around 10 cm in diameter. In this logging tool, plastic scintillators were scaled down to achieve a high angular resolution for the incoming muon direction and were rotated mechanically to give a wider view of incoming muon particles. The verification of the logging tool function was conducted in a horizontal borehole located beneath a small mountain at a depth of 50 m. The density distribution of the mountain obtained via muography with the logging tool was roughly consistent with the density values measured by using cores in a borehole drilled adjacent to the mountain. We also discussed the application of muography in a deep borehole using the logging tool and the tool’s suitability for muography in oil and gas resource development, CO2 geological storage, methane hydrate resource development, underground hydrocarbon energy storage, compressed air energy storage, and geothermal power.
