Geophysical Logging and Hydraulic Testing, Pahute Mesa, Nevada Test Site^a

Abstract

The U. S. Geological Survey, on behalf of the U. S. Atomic Energy Commission, performs a broad range of geologic and hydrologic studies related to underground nuclear explosions at the Nevada Test Site. One phase of the studies involved extensive geophysical logging and hydraulic testing in deep exploratory holes at Pahute Mesa, Nevada Test Site. Various geophysical logs and hydraulic testing techniques used in the study are described in this paper. Interpretations of logs and logging techniques depend on factors such as rock characteristics in a particular area, drilling methods, and the objectives of the hydrologic investigations. From experience gained at Pahute Mesa, some qualitative data on rock lithologies and hydraulic conditions in the borehole may be determined by electric, caliper, temperature, and fluid resistivity logs. Quantitative data on the major water‐yielding intervals in the borehole are obtained from radioactive tracer or spinner surveys. Interpretations of the geophysical logs have been verified by isolating specific zones in the drill holes with inflatable packers and spacers. These intervals were tested by injection or swabbing of fluid and measuring the resultant change in water level caused by fluid outflow from or inflow to the interval of rock isolated by the packers.

Straddle-packer determination of the vertical distribution of hydraulic properties in the Snake River Plain Aquifer at well USGS-44, Idaho Chemical Processing Plant, INEL

“…(B) is a multi-level ported casing with movable inner packer similar to the system described by Bottomley et al (1984). (C) is a straddle-packer system deployed in an open borehole similar to the straddle-packer used for hydraulic testing in Blankennagel (1968) and in this report.…”

“…feet deep (Blankennagel, 1968 3. Characterize and quantify changes in hydraulic conductivity with depth.…”