51 Figure 15 Energy applications for different borehole depths. Hole depths above 10km cannot be realized using conventional technologies. Quaise develops a Millimeter Wave Drilling (MMWD) system that originates form MIT’s Plasma Science and Fusion Center. MMWD does not rely on mechanical drill bits to grind through rock, but uses chemical interactions to vaporize the rock, which is returned in particle form to the surface. Quaise aims to build on the Enhanced Geothermal Systems (EGS) concept, leveraging the fact that at high depths the geothermal fluid is in a supercritical phase, allowing for high energy densities. They assume that the electricity output for a wellfield of 8 wells would be 44MWelectric and 750,000lb/hr of heat (using hot water at 125C). Their current estimate is that the technology will be available in 2040 and that it would then take around 2 years for the wellfield development (assuming 8 wells). To realize the project, Quaise proposes conventional drilling for a depth of 1km, followed by MMWD to a target depth of 20km. This second stage would drill through igneous rock (4.8km) and crystalline rock. They propose drilling 8 wells (4 for injection and 4 for production), with each well requiring 5 acres and a separation of 500m between wells, leading to a surface footprint of 0.75km2. To further explore the feasibility of this project will require siting studies and permitting discussions with local governments. The total cost to reduce MIT’s current CUP is estimated by Quaise at $457M. If the project were to be implemented to fully replace the fossil fuels powering, MIT’s CUP, carbon emissions would be zero. According to Quaise, the cost of drilling with the MMWD system increases linearly with depth. The cost of each well is assumed to be $1,133,861 for conventional drilling, $42,926,393 for MMWD, $3,650,000 for stimulation, $2,8M for wellpads. Drilling half of the wells would therefore decrease the cost by approximately $200M, down to $254M (note that the power plant costs – conversion of the CUP – are fixed capital costs).
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