| Abstract |
Geothermal power promises clean, renewable, reliable and potentially widely-available energy, but is limited by high initial capital costs. New drilling technologies are required to make geothermal power financially competitive with other energy sources. One potential solution is offered by Thermal Spallation Drilling (TSD) - a novel drilling technique in which small particles of rock (spalls) are released from the rock surface by rapid heating. While TSD has the potential to improve drilling rates of brittle granitic rocks, the coupled thermomechanical processes involved in TSD are poorly described, making system control and optimization difficult for this drilling technology. In this presentation, we discuss results from a new modeling effort investigating thermal spallation drilling. In particular, we will focus on results from explicit small models investigating the grain-scale mechanics of thermal spallation and compare these simulations with existing theories concerning spalling mechanisms. We will report how microstructure (particle size distributions and volume fractions), grain properties and borehole conditions influence spall production, and discuss implications for macro-scale models of drilling systems. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. |