Geophysical Borehole Logging in the Unsaturated Zone, Yucca Mountain, Nevada

by Ulrich Schimschal, U.S. Geological Survey, Denver, United States,
Philip H. Nelson, U.S. Geological Survey, Denver, United States,

Document Type: Proceeding Paper

Part of: High Level Radioactive Waste Management 1991


Borehole geophysical logging for site characterization in the volcanic rocks at the proposed nuclear waste repository at Yucca Mountain, Nevada, requires data collection under rather unusual conditions. Logging tools must operate in rugose, dry holes above the water table in the unsaturated zone. Not all logging tools will operate in this environment, therefore; careful consideration must be given to selection and calibration. A sample suite of logs is presented that demonstrates correlation of geological formations from borehole to borehole, the definition of zones of altered mineralogy, and the quantitative estimates of rock properties. We show the results of an exploratory calculation of porosity and water saturation based upon density and epithermal neutron logs. Comparison of the results with a few core samples is encouraging, particularly because the logs can provide continuous data in boreholes where core samples are not available.

Subject Headings: Boring | Radioactive wastes | Geology | Rocks | Rock properties | Waste disposal | Waste sites | Volcanic deposits | Nevada | United States

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