ECONOMIC BREAKTHROUGHS FOR GEOTHERMAL ENERGY: SUPER HOT EGS AND THE NEWBERRY DEEP DRILLING PROJECT

Meeting the future electrical demand with clean power is a huge challenge facing the warming planet. The ideal energy source will be carbon-free, dependable, flexible, widely-deployable, have high energy density, and be low cost. Geothermal energy fits these criteria very well. Enhanced geothermal systems (EGS) and deep geothermal heat systems are enjoying economic success, particularly in the EU. However, this success requires a combination of significant pre-engineered formation permeability, nearby thermal-heat users, and large feed-in tariffs for the electricity generated.

A new type of geothermal energy, called Super Hot Rock (SHR), will make EGS more scalable. A productive geothermal well drilled into SHR above 400°C will produce super-critical fluid. At a flow rate of 60 L/s a SHR well could produce 50 MWe compared to 5-7 MWe for the same flow at 200°C. Even though these super hot wells will be cost more, the high energy density means EGS can meet the market if we drill hotter and deeper to directly tap the heat source. The plan is to start where hot rock is close to the surface (~5 km), lowering the cost of SHR EGS drilling, and testing. Eventually, advanced drilling methods such as energy drilling and casing-while-drilling, could allow wells to be economically drilled to 20 km, expanding SHR to 80% of the world’s population.

A suitable SHR site in the PNW is on Newberry Volcano, one of the largest geothermal heat reservoirs in the USA, extensively studied for the last 40 years. Millions of dollars have already been invested in the site by private geothermal developers and the US DOE, resulting in a ready-to-use facility with the necessary infrastructure, environmental permits, land commitments, and monitoring plans. An idle geothermal exploration well drilled in 2008, 3.5 km deep and 320°C at bottom, will be evaluated for deepening another 1.5 km to reach temperatures above 450°C.

The first step toward developing the Newberry SHR site was an International Continental Drilling Program sponsored workshop held at the OSU-Cascades campus in Bend from Sept. 10-14, 2017. Important scientific questions related to breakthroughs in geothermal energy, drilling at extreme temperatures, seismology, and volcanology were discussed by more than 40 engineers and scientists. The final report and funding plan will be available soon.