Description: Permeability of quartz monzonite from the Los Alamos hot-dry-rock geothermal well GT-2 was experimentally measured as a function of pressure and temperature. Permeability of the GT-2 rocks from depths of 8580 ft and 9522 ft behaves like Westerly granite for changes in effective confining pressure. However, permeability of these rocks behaves much differently with increasing temperature. As temperature is increased, the permeability of Westerly granite passes through a slight minimum and then increases exponentially above 100/sup 0/C. Upon cooling the permeability shows a permanent increase of up to four times its original value. The permeability of GT-2-9522', on the other hand, drops off exponentially with increasing temperature, reaching a minimum near 140/sup 0/C; above 150/sup 0/C, permeability rises slowly. These changes in permeability with temperature are postulated to be caused by differential thermal expansion (DTE), a phenomena related to the anisotropic and inhomogeneous coefficients of thermal expansion of the mineral grains in the rock. Scanning electron photomicrographs of unheated and heated samples of Westerly and GT-2 rocks support the DTE hypothesis. Differences in the behavior of these rocks with temperature are believed to be due to the respective temperature and pressure environments in which they became equilibrated, since both GT-2 rocks had existed at moderately high temperatures and pressures for some time. Temperature disequilibrium of the GT-2 rocks in their present in situ environments is believed to have caused the differences in the behavior between the two samples and may provide a method for determining the pre-intrusion geothermal gradient of the Jemez area. Flow channels were observed in GT-2 samples using radioactive tracer techniques. Several radioactive isotopes were tried in these experiments, including /sup 22/Na, /sup 63/Ni, and /sup 35/S.
Date: May 1, 1978
Creator: Potter, J.M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department