Book Description

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.