Geothermal well technology and potential applications of Subterrene devices: a status review

The past, present, and some future aspects of the geothermal energy (GTE) industry have been reviewed with special attention given to geothermal well-drilling problems. Geothermal wells can be produced with present equipment and methods, mostly derived from the oil and gas industry, but costs are relatively high. Short-term improvements are needed in drilling rigs and auxiliary surface equipment, drill bits, bit-bearing lubrication systems, tubular goods, high-temperature muds and cements, logging and downhole sampling equipment, directional control equipment applicable to geothermal conditions,and in the use of a data bank for GTE wells to help optimize drilling programs. Two types of wells are needed: (1) small-diameter wells for exploration, reinjection, and disposal purposes, and (2) larger-diameter wells for production. To develop and greatly expand the use of GTE in the future, new methods and equipment are needed to penetrate hard abrasive rocks and to provide hole stabilization and support at the very high temperatures and other extreme conditions which can be encountered in GTE wells. New Los Alamos Scientific Laboratory concepts for penetrating rocks by use of rock-melting processes (called Subterrene concepts) offer potential solutions to some difficult GTE well-production problems.