Laboratory Study and Field Demonstration of Hydrothermal Spallation Drilling

Abstract

Hydrothermal spallation drilling has been demonstrated for the first time under controlled laboratory conditions and deployed in shallow field trials. Multiple laboratory-scale drilling experiments have produced 1-inch diameter boreholes in 4-inch diameter rock cores under conditions simulating deep boreholes at drilling rates up to 30 ft/h in rocks such as granite, granodiorite, sandstone, and quartzite. In addition, 4-inch diameter boreholes have been produced in 24 x 24 x 36-inch granite monoliths at rates up to 40 ft/h. The hydrothermal spallation drilling technology has also been tested in the field. A prototype bottom hole drilling assembly deployed on a coiled tubing unit was fielded in competent granite in the western Sierra foothills of northern California. This paper describes the results of the new drilling technology in the laboratory and field trialsas well asits application to reducing hard rock drilling costs of hydrothermal and EGS reservoirs.