The National Advanced Drilling and Excavation Technologies (NADET) Program: A New Collaborative Research and Development Initiative

Abstract

Abstract Geothermal energy, heat energy stored in the earth, is exploited for the generation of environmentally clean, reliable electric power and for direct heat applications such as space and water heating, aquaculture and agricultural operations, enhanced oil recovery, mining, and industrial processing. With 2800 megawatts of installed electric capacity generating 15 billion kilowatt-hours per year and 18 trillion Btu per year utilized in direct-heat applications in the U.S., expanded market penetration is often hampered by higher costs associated with geothermal energy development. A significant portion of these higher costs is directly or indirectly dependent on drilling wells to discover, delineate, and produce geothermal resources. The Geothermal Division of the U.S. Department of Energy has proposed a national R&D initiative involving government, national laboratory, industry, and academic stakeholders to develop less costly ways of penetrating rock. The goal of this proposed program is to develop an advanced and innovative drilling system by the year 2000 for use by the geothermal industry and other industry sectors including oil and gas, mining, underground storage, and civil infrastructure. The Potential of Geothermal Energy Geothermal energy, heat energy stored in the earth, originates from the earth's molten interior and from the decay of radioactive elements in the crust. This heat has been used for centuries for cooking, hot baths, and therapeutic purposes. Today, geothermal energy is exploited for the generation of environmentally clean, reliable electric power and for direct-heat applications such as space and water heating, aquaculture and agricultural operations, enhanced oil recovery, mining, and industrial processing. Most commercial geothermal fields were discovered because of nearby hot springs, fumaroles, geysers, and other surface manifestations. There are four types of geothermal resources which are classified according to their predominant properties. Hydrothermal resources have steam and/or hot water trapped in porous or fractured rocks at shallow to moderate depth. Of the resource types, only hydrothermal resources have been commercially utilized. Geopressured reservoirs are highly pressurized and contain hot water and natural gas in sandstones that are overlain by impermeable shales. Heat in hot, but essentially water-free, impermeable rock at accessible depths is known as hot dry rock resources. Molten or partially molten rock at accessible depths in the earth's crust are classified as magma resources. P. 693