Published on 06 January 2021

Report on ‘Risk assessment for Ultra-Deep Geothermal Energy and Enhanced Geothermal Systems, and an inventory of preventive and mitigating measures’ has been published

An international consortium led by Witteveen+Bos and consisting of VITO, Q-Con, Newell and TU Delft has created a risk inventory and framework for risk management in relation to Ultra-Deep Geothermal Energy (UDG) and Enhanced Geothermal Systems (EGS). The research forms part of the Knowledge Programme on the Effects of Mining (KEM) initiated by the Dutch Minister of Economic Affairs. The results were published on 4 January 2021 by the State Supervision of Mines (SodM).

Dutch society faces a major challenge in increasing the sustainability of its energy systems. Ultra-Deep Geothermal energy is being stimulated as a source of sustainable heating by the Ministry of Economic Affairs and Climate Policy together with Energie Beheer Nederland. In the Netherlands, geothermal systems at a depth greater than 4 km are considered ultra-deep. Temperatures at these depths can range between 120 and 250 °C. At such depths, the application of EGS may be required. EGS uses stimulation methods to improve the permeability of a reservoir.

In the Netherlands, there is currently no experience with UDG or EGS. There is also no risk inventory available in the field, mining legislation in its current form is not suitable for UDG/EGS projects, and there is a general lack of knowledge regarding the deeper subsurface. For this reason, an international team was assembled with experts on drilling, stimulation, testing, operating and induced seismicity from within the Netherlands and abroad. The team combined knowledge obtained from literature with their own experience and translated this to the situation in the Netherlands.

The research provides an overview of the health, safety and environmental risks of UDG and EGS in the Netherlands. The identified risks were translated using a bow-tie analysis into a classification system that allows for project-specific risk assessment which helps identify mitigating measures. The report is intended to assist the State Supervision of Mines in their advisory role to the Ministry of Economic Affairs and Climate on aspects of health, safety and environmental impact with respect to geothermal developments.