Hydrothermal Spallation for the Treatment of Hydrothermal and EGS Wells: A Cost-Effective Method for Substantially Increasing Reservoir Production and Flow Rates

Abstract

A hydrothermal spallation-based approach to altering the geometry of wellbores to reduce near wellbore impedance and increase well productivity has been demonstrated for the first time under controlled laboratory conditions and in shallow field trials. In the laboratory, hydrothermal spallation-based wellbore shaping tools have been used to create vertical slots in existing boreholes. Prototype slotting tools created deep channels in the granite walls of existing boreholes with both single and dual opposing slot geometries. The interaction of the hydrothermal jet with tight fractures, various reservoir rock types, and the effect of in-situ rock temperature has also been examined. The hydrothermal spallation slotting concept was also deployed in a shallow, non-geothermal field environment. A prototype bottom hole slotting assembly mounted on a coiled tubing drilling unit was fielded in the competent granite in the Sierra foothills near the town of Raymond, CA. Both single and triple slotted holes were produced at a depth of 300 ft. Slots up to 16 inches deep with increases in effective borehole diameters of up to ten fold were readily achieved as determined by volumetric measurements. Combined with 3D reservoir modeling studies presented in a separate paper at this meeting, this work suggests that the hydrothermal spallation slotting technology can be used to reduce near wellbore impedance and increase the productivity or injectivity new and existing hydrothermal wells. Plans to demonstrate the technology in hydrothermal environments will be presented.