| Title | Assessing the Environmental Impacts of Deep Geothermal Drilling in the ORCHYD Project |
|---|---|
| Authors | Vasileios Papakostas, John Paravantis, Nikoletta Kontoulis, Naveen Velmurugan, Florian Cazenave |
| Year | 2023 |
| Conference | World Geothermal Congress |
| Keywords | Life Cycle Assessment, Ecological Footprint Assessment, environmental impacts, deep geothermal drilling, ORCHYD project |
| Abstract | This paper examines the environmental impacts of the ORCHYD (Novel Drilling Technology Combining Hydro-Jet and Percussion For ROP Improvement in Deep Geothermal Drilling) Horizon 2020 project in a holistic manner. ORCHYD’s goal is to increase the rate of penetration (ROP) of hard rock drilling from 1 to 2 meters per hour (m/h) to 4 to 10 m/h by combining two previously distinct, mature technologies: High Pressure Water Jetting (HPWJ) and Percussive Drilling. Based on a literature review, the environmental impacts of deep geothermal energy development on the lithosphere, atmosphere, hydrosphere, and biosphere were cataloged and assessed. These were compared to the novel drilling techniques developed by ORCHYD. Lithospheric impacts concerned soil subsistence; microseismicity; soil profile; groundwater; solid waste; land use; and visual intrusion. Impacts related to the hydrosphere concerned water quantity and quality as well as wastewater. Atmospheric impacts concerned greenhouse gas emissions; local air pollution; odors; and noise. Lastly, impacts on the biosphere concerned ecosystems; human health; socioeconomic issues; material use; energy consumption; and energy security. Impacts were characterized on the basis of six different categories. Positive/negative to the environment; temporary/long term; reversible/irreversible; direct/indirect (nature): direct or indirect; not likely/potential/certain; and local/regional/national/international. The importance of impacts was assessed by the partners via an online scoping survey. The assessment of impacts considered most important was complemented with a Life Cycle Assessment (LCA). The LCA was based on an assessment of alternate drilling scenarios. LCA considered ozone depletion, smog, acidification, eutrophication, and energy use for drilling, in addition to carbon emissions, which were measured in carbon dioxide equivalents. The effect of the distance between geothermal operations and major urban areas, as well as the effect of drill bit usage lifetime, were also taken into account. In comparison to ROP rates of 2 m/h in hard rock formations, scenarios with ROP rates of 4 to 10 m/h may result in the following reductions: carbon dioxide equivalent by 65.2%; energy consumption (as MJ surplus) by 68.9%; chlorofluorocarbons (CFC) equivalent by 3.8%; ozone equivalent by 66.2%; sulfur dioxide equivalent by 66.7%; and nitrogen equivalent by 67.1%. An Ecological Footprint Assessment (EFA) supplemented the LCA study from a biocapacity perspective expressed in global hectares, and found that the ecological footprint of geothermal drilling was reduced by 65.2%. All in all, most impact categories were inversely proportional to ROP. It was concluded that ORCHYD technologies may reduce emissions and the average energy required for drilling per meter, thus improving the environment profile of deep geothermal drilling. Dhar, A., Comeau, P.G., Karst, J., Pinno, B., Chang, S., Naeth, M.A., Vassov, R., & Bampfylde, C.: Plant Community Development Following Reclamation of Oil Sands Mine Sites in the Boreal Forest: A Review. Environmental Reviews, 26(3), (2018), 286–298. Lacirignola, M., Meany, B. H., Padey, P., & Blanc, I.: A Simplified Model for the Estimation of Life-Cycle Greenhouse Gas Emissions of Enhanced Geothermal Systems. Geothermal Energy, 2(8), (2014). Thomas, L. K., Tinjum, J. M., & Holcomb, F. H.: Environmental Life Cycle Assessment of a Deep Direct-Use Geothermal System in Champaign, Illinois. In 45th Workshop on Geothermal Reservoir Engineering. Stanford University, Stanford, California (2020). Vidal, J., Genter, A., & Schmittbuhl, J.: How Do Permeable Fractures In the Triassic Sediments of Northern Alsace Characterize the Top of Hydrothermal Convective Cells? Evidence from Soultz Geothermal Boreholes (France). Geothermal Energy, 3(1), (2015). Wackernagel, M., Schulz, N. B., Deumling, D., Linares, A. C., Jenkins, M., Kapos, V., Monfreda, C., Loh, J., Myers, N., Norgaard, R., & Randers, J.: Tracking the Ecological Overshoot of the Human Economy. Proceedings of the National Academy of Sciences, 99(14), (2002), 9266–9271. |