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Thermal Spallation and of Rock Using Supercritical Water

Researcher: Adam Carr
Principal Investigator: Professor Jefferson Tester

An obstacle hindering implementation of EGS is the large up-front capital costs for drilling and reservoir stimulation. For EGS to become more economically viable, particularly in low grade regions, new drilling technologies such as hydrothermal jet drilling are being developed that could significantly reduce the cost to drill the deeper wells needed for low-garde EGS. Hydrothermal flame drills create a jet of supercritical water which impacts and heats the rock, causing the rock to 'spall', i.e., eject small rock fragments to relieve thermal and mechanical stress. Hydrothermal drilling has the potential to lower drilling costs over conventional methods by increasing penetration rates and avoiding the transit time associated with replacing worn drill bits and transporting the drill string out of the well.

Although focused on experimental studies, the project has also theoretical part in parallel. The drilling rates will be measured by analyzing reactor exit stream chemical compositions, reactor temperature distributions and remnant rock properties. In order to understand drilling mechanics, models of the different chemical processes occurring in the reactor will be made from the current state of the art, and reconciled to experimental results. The developed models will take into account transport of rock spalls in the wellbore and heat transfer effects throughout the process. The research conducted in this project will hopefully lead to an increased understanding of the mechanisms of rock spallation/dissolution, as well as demonstrate the commercial viability of a novel drilling method.