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Archäologie im Rheinland, 2013(2014)

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2019; Aachen 1 Online-Ressource (192 Seiten) : Illustrationen, Diagramme (2019). = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2019, The generation of hydraulical fractures is not only applied in the production of hydrocarbons, but also in the enhanced activation of geothermical energy. However, comprehensive knowledge of the rocks‘ parameters, the stress regime and other influencing factors are necessary for optimal results. The aim of this study is to identify the mechanical behavior of selected sandstones in regard of their ability to grow fractures under consideration of different fracking-fluid characteristics. The gained results are to give a more thorough concept of fracture growth in the geological subsurface. This will allow for a better understanding of the utilization of artificially generated fractures in reservoirs. As apart from fluid mechanics, fracture mechanics is the controlling factor for fracture propagation, the processes at the fracture tip will be adressed. A short consideration of the theoretical fundamental principles will be followed by an introduction of technical possibilities to evaluate the fracture toughness in a laboratory setting. Mechanical trials will be performed on five different sandstone samples, complemented by the CCNBD-concept. Furthermore, a numerical simulation was conducted, in order to learn about the geometrical modelling influencing the fracture initiation. In the results, a high dependency of the mechanical behavior of the rock on water saturation could be found. Further, the results indicate correlations between different rock characteristics. This partially allows to approximate values for missing parameters, if others are available. It could be shown, that the dielectric constant and the surface tension of a fracking fluid have influence on the tensile strength, but not the fracture toughness., Published by Aachen