The Los Alamos scientific laboratory dry hot rock geothermal project (LASL Group Q-22)

Abstract

An exploratory hole 785 m (2576 ft) deep was drilled in Barley Canyon, about 5 km (3 miles) outside the western geologic rim of the Valles Caldera in New Mexico. This hole, identified as ''GT-1'', penetrated about 143 m (470 ft) into the granitic Precambrian rock. Bottomhole temperature was 100.4/sup 0/C. Hydraulic fracturing was accomplished repeatedly in the granitic section of the hole at pumping pressures of the order of 10.3 MPa (1500 psi). The fractures appeared to be essentially vertical and to have a consistent northwest-southeast orientation. The fractures could be held open by pumping pressures of the order of 6.9 MPa (1000 psi), and at such pressures the rate of fluid loss from the system was very low. It was concluded that the basement rock penetrated by GT-1 was well suited to creation and containment of a pressurized-water energy-extraction loop. A second deep exploratory hole, GT-2, has been drilled to a present depth of 2042 m (6701 ft). It is located on top of Fenton Hill, a flat-topped mesa about 2.5 km (1.5 miles) south of GT-1. It is being used primarily to investigate the structure, temperature, permeability, and fracturing behavior of the Precambrian basement rock at amore » second location and at greater depth than was reached in GT-1. Discussions of the geology, site selection, drilling, core studies, heat flow and hydraulic fracturing primarily for the GT-2 exploratory hole are presented.« less