Turan, A. ; Bär, K. ; Afshari Moein, M. ; Sass, I. (2019)
Geothermal Modelling of Variscan Enhanced Geothermal System in Granitic and Metamorphic Rocks.
10th European Geothermal PhD Day 2019. Potsdam, Germany (25.-27.02.2019)
Konferenzveröffentlichung, Bibliographie

Kurzbeschreibung (Abstract)

With the ambition to achieve European Union (EU)’s energy directive, that is 20% final energy consumption from renewable sources by 2020 then upscaled to 30% by 2030, all EU countries have adopted their national energy action plans to include more projects on low carbon thermal and electrical power generation technologies. One sustainable way to achieve this target can be the utilization of geothermal resources since they are capable of not only being utilized for heating purposes as well as power generation but also providing base load that eliminates the need for heat storage. Up to now, hydrothermal systems have restricted the widespread use of geothermal resources by its limited geological application areas. Now, unconventional Enhanced Geothermal Systems (EGS) promise the dissemination of geothermal resources in spite of decreasing know-how and increasing drilling depths. This study, as a part of ‘Multidisciplinary and multi-context demonstration of EGS exploration and Exploitation Techniques and potentials (MEET)’-EU funded project, aims to minimize the uncertainty by providing high quality datasets measured on field analogues of potential reservoir rocks accompanied by developed numerical models and to minimize the drilling costs by focusing on the sites that already have certain infrastructure. To meet these targets; firstly the geological settings of four different test sites, which are representative of the European Variscan basement, will be characterized. To do that, information will be gathered about three main European continental crust rock types i.e. fractured granites, sediments, and non-granitic basement rocks; namely Variscan low-grade metasedimentary and metavolcanic rocks, since all these three represent 70% of EU surface as potential EGS reservoirs. Petrophysical measurements (grain and bulk density, porosity, permeability, compressive and shear velocity, thermal conductivity, thermal diffusivity, heat capacity and radiogenic heat production) and rock mechanical property characterizations (uniaxial compressive strength, tensile strength, shear strength, cohesion, coefficient of friction, Poisson’s ratio, Young’s modulus, bulk modulus, shear modulus, compressibility, Biot and Skempton coefficients) will be done on the representative samples in the laboratory of Applied Geoscience Institute in Technical University of Darmstadt in collaboration with project partners. Secondly, thermal-hydraulic-mechanical-chemical (THMC) simulation concepts will be implemented to increase the stimulation efficiency and to forecast the sustainability of operation at different test sites. Thus, the acquired information at the first step will be used as input parameters in the models. These initial models will be the platform to integrate the obtained data and will improve our understanding of the geothermal system at the outcrop analogue and/or reservoir scale. Finally, chemical stimulation strategies will be drawn up and tested in Variscan fractured granite, based on the experience gained in ongoing EGS projects such as Soultz-sous-Forêts and Rittershoffen. This strategy will be then applied to the United Downs Deep Geothermal Power (UDDGP) project (in Redruth, Cornwall-United Kingdom) where a sub-vertical fault zone within the Variscan Carnmenellis Granite is targeted to be penetrated.

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