Final Report Of Geothermal Energy And High Performance Drilling Collaborative Research Program Gebo

The superior goal of the gebo research association was making important contributions for the future reliable drilling under the existing “hot-hard-rock” conditions in Niedersachsen and their development to the geothermal drillings with sustainable geological subsurface heat exchangers. This goal should be achieved due to the solid research and innovative technology approaches in their combination within one concept for pioneering methods in deep geothermal drillings in hard rock, to be more exact - in interdisciplinary cooperation on engineers and scientists - in cooperation between industry and University, researchers and users Gebo research association comprised scientists and technicians of different research institutions and universities who are working in 33 projects. The individual projects were assigned to one of the 4 main research fields or focus areas. Gebo research association started its activities with 7 project partners participating: - Technische Universität Braunschweig (TUBS) - Technische Universität Clausthal (TUC) - Gottfried Wilhelm Leibniz Universität Hannover (LUH) - Georg-August-Universität Göttingen (UGOE) - Leibniz-Institut für Angewandte Geophysik (LIAG) - Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) - Energie-Forschungszentrum Niedersachsen (EFZN) Baker Hughes, an industrial partner, participated in the association and supplies it with its experience and additional funds.

The Federal program's goal, strategy, plans, and achievements are summarized. In addition, geothermal development by state and local governments and, where available, by the private sector is described.

One of the major factors presently inhibiting the exploitation of geothermal energy is the high cost of drilling and completing geothermal wells. The cost of these wells typically ranges from $1 M to $3 M, which are several times that of an oil or gas well of comparable depth. These high costs are primarily driven by the harsh environment associated with geothermal reservoirs. The high temperatures which are inherent to the resource cause rapid degradation of conventional drill bits and preclude the use of conventional drilling fluids. Geothermal formations are typically hard and highly fractured. This results in low rates of penetration, high rates of drilling fluid loss, and difficulties in obtaining competent completions. The chemical composition of the downhole geothermal fluids causes extensive scaling, and combined with high temperatures, cause corrosion of drill pipe, casing, and logging equipment. Current activities include development of high temperature drilling fluids, methods for plugging lost circulation zones, advanced rock cutting techniques, and borehole instrumentation. Three specific projects which are being pursued, each at a different stage of development include: a method for locating fractures which do not intersect the wellbore, a laboratory for simulating lost circulation zones--to be used for development of new materials and techniques, and the understanding of the capabilities and limitations of PDC bits in the geothermal environment.