The project aims at demonstrating different stimulation techniques in order to allow for an economic provision of geothermal energy from low productive reservoirs.
Enhanced geothermal systems (EGS) allow a widespread use of the enormous untapped geothermal energy potential. EGS measures are generally intended to improve productivity (or injectivity) of a geothermal reservoir by increasing the overall transmissivity of the reservoir rocks. This goal can be achieved by various methods that are dependent on the geological system, comprising the rocks, the rock structures, the tectonic situation as well as the stress field. Besides the controlled enhancement of the reservoir, the sustainable operation of the system presents a challenge, as newly opened fractures may close again with reduced reservoir pressure and because of chemical interaction with the fluid, which may lead to neoprecipitation and reduced permeability. Another challenge lies in the side effects of hydraulic treatments, as the high fluid pressures applied and the large fluid volumes injected in such treatments sometimes induce seismic events that can, in some cases, be felt at the surface and jeopardize the public acceptance of a project. These issues will be addressed by the DESTRESS project. The project aims to demonstrate a concept-based approach to develop an EGS that takes the site-specific geological requirements into account. DESTRESS has three overall objectives: i) increase transmissivity of the reservoir, ii) maintain productivity of the system and iii) minimise the level of induced seismicity. The concepts are based on experience in previous projects, on developments in other fields, mainly the oil & gas sector, and on scientific progress made on topics such as fluid-rock interaction, the improved determination of the stress field and on the analysis of induced seismicity. For the demonstration in various geological environments representative for large parts of Europe (representing ~80 % of rock types and adequate settings), the DESTRESS concept will be applied at several sites. In general, we will use a “soft stimulation” approach, which implies a stimulation treatment with minimised environmental hazard, to enhance the reservoir performance in several geological settings covering granites, sandstones, and other rocks, and systems where operations have caused significant reduction in productivity due to mineral precipitation. In all cases, risks will be managed at the specific sites with a demonstration of the reduced environmental footprint, and lessons learned will be disseminated to the public. Risk management will also include the demonstration of non-standard risk monitoring or tools controlling performance. The business cases will be shown with cost and benefit estimations based on the proven changes of system performance. All the steps included in the DESTRESS approach are designed to be transferrable to other sites, such that the concepts can become the basis for a standardized procedure in the development of EGS projects.