High-temperature directional drilling turbodrill

The development of a high-temperature turbodrill for directional drilling of geothermal wells in hard formations is summarized. The turbodrill may be used for straight-hole drilling but was especially designed for directional drilling. The turbodrill was tested on a dynamometer stand, evaluated in laboratory drilling into ambient temperature granite blocks, and used in the field to directionally drill a 12-1/4-in.-diam geothermal well in hot 200/sup 0/C (400/sup 0/F) granite at depths to 10,5000 ft