Presenter
Prof. Dr. Ernst Huenges
Senior Scientist
Section 4.8 Geoenergy
Helmholtz Center Postdam
GFZ German Research Centre for Geoscience
Abstract
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 is envisaged 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 precipitation 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 be felt at the surface or even provoke damage and jeopardize the public acceptance of a project. These issues are addressed by the DESTRESS project (Demonstration of soft stimulation treatments in geothermal reservoirs). 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) minimize the level of induced seismicity. The concepts are based on experience in previous projects, on developments in other fields, mainly the oil & gas sector, 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.
