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Geofluids
Volume 2017, Article ID 4653278, 15 pages
https://doi.org/10.1155/2017/4653278
Research Article

On the Role of Thermal Stresses during Hydraulic Stimulation of Geothermal Reservoirs

Center for Hydrogeology and Geothermics (CHYN), Laboratory of Geothermics and Geodynamics, University of Neuchâtel, Neuchâtel, Switzerland

Correspondence should be addressed to Gunnar Jansen; hc.eninu@nesnaj.rannug

Received 30 March 2017; Accepted 18 May 2017; Published 28 June 2017

Academic Editor: Weon Shik Han

Copyright © 2017 Gunnar Jansen and Stephen A. Miller. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Massive quantities of fluid are injected into the subsurface during the creation of an engineered geothermal system (EGS) to induce shear fracture for enhanced reservoir permeability. In this numerical thermoelasticity study, we analyze the effect of cold fluid injection on the reservoir and the resulting thermal stress change on potential shear failure in the reservoir. We developed an efficient methodology for the coupled simulation of fluid flow, heat transport, and thermoelastic stress changes in a fractured reservoir. We performed a series of numerical experiments to investigate the effects of fracture and matrix permeability and fracture orientation on thermal stress changes and failure potential. Finally, we analyzed thermal stress propagation in a hypothetical reservoir for the spatial and temporal evolution of possible thermohydraulic induced shear failure. We observe a strong influence of the hydraulic reservoir properties on thermal stress propagation. Further, we find that thermal stress change can lead to induced shear failure on nonoptimally oriented fractures. Our results suggest that thermal stress changes should be taken into account in all models for long-term fluid injections in fractured reservoirs.