[FISH] Andrew Seltzman (MIT PSFC)

“Brimstone: A New Computational Model Integrating Microwave Physics with Drilling Economics for Ultra-Deep Geothermal Access”

Superhot-rock geothermal energy could provide clean power generation over broad geographic areas if economical access to deep crystalline rock becomes feasible. Conventional drilling becomes prohibitively expensive beyond 5 km depth, while millimeter-wave (MMW) drilling offers an alternative by using high-power electromagnetic radiation to ablate rock without mechanical contact. We present Brimstone, a simulation package that couples microwave physics to drilling economics – providing the first comprehensive model for evaluating economic viability of MMW drilling for superhot-rock geothermal access at 10–15 km depths. This simulation integrates first-principal RF transmission physics, borehole pressure management, drilling operations, and project economics. RF losses from ohmic dissipation are small compared to loss contributions from waveguide junction angular misalignment and pressure-driven absorption on the nitrogen-filled waveguide.

By coupling RF simulations with drilling simulations tracking pressure constraints and casing requirements, an economic analysis reveals that rig time dominates borehole cost, largely due to time for waveguide segment insertion and casing operations to maintain borehole pressure between blowout and fracturing limits as a nitrogen borehole fill provides lower hydrostatic pressure than conventional drilling mud. Frequent casing operations are necessary, demanding time-consuming waveguide withdrawal and reinsertion. For 15 km boreholes in crystalline rock, predicted costs range from $160–250 million and LCOE of $250–395/MWh-e for a 250 MWe plant when utilizing currently available casing operations used in mechanical drilling applications. MMW drilling may enable in-situ generation of a vitrified glass borehole casing, increasing the incremental depth between casing operations and reducing borehole cost. Development of vitrified glass casings, improved waveguide insertion times, and transmission line engineering may reduce the LCOE of superhot-rock geothermal to be competitive with near surface plants.

Friday Informal Seminar Hour —

Postdoc-run seminar series within the Earth Resources Laboratory (ERL). Features talks by ERL members as well as special guests from academia and industry on earth science and energy transition topics including geothermal energy, carbon sequestration, geologic hydrogen, and critical minerals / in situ mining.

Contact:  fish_seminar_organizers@mit.edu