eprintid: 1828 rev_number: 16 eprint_status: archive userid: 6 dir: disk0/00/00/18/28 datestamp: 2017-03-02 10:20:53 lastmod: 2017-05-16 12:21:39 status_changed: 2017-03-02 10:20:53 type: article metadata_visibility: show creators_name: Jeanne, Pierre creators_name: Rutqvist, Jonny creators_name: Dobson, Patrick F. creators_name: Walters, Mark creators_name: Hartline, Craig creators_name: Garcia, Julio corp_creators: Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley,USA corp_creators: Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley,USA corp_creators: Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley,USA corp_creators: Calpine Corporation, USA corp_creators: Calpine Corporation, USA corp_creators: Calpine Corporation, USA title: The impacts of mechanical stress transfers caused by hydromechanical and thermal processes on fault stability during hydraulic stimulation in a deep geothermal reservoir subjects: MP4 subjects: MP6 subjects: RU1_1 subjects: SG divisions: SHEER-5 full_text_status: none abstract: We performed a series of 3D thermo-hydro-mechanical (THM) simulations to study the influences of hydromechanical and thermal processes on the development of an enhanced geothermal system, strongly influenced by a network of short fault zones. The model we developed was calibrated by comparing the simulated THM responses to field observations, including ground-surface deformations, well pressure, and microseismic activity. Of particular importance was the comparison between the observed temporal and spatial distribution of microseismic activity, and the calculated shear reactivation of preexisting fractures inferred from simulated elasto-plastic mechanical responses in the short fault zones. Using this approach, we could identify when fault zones were reactivated (as manifested in the field by a surge of local microseismic activity within the fault zone), and we could back-calculate the in situ stress field as being close to the stress conditions required for shear reactivation. Our results show that the main mechanisms of inducing seismicity are related to injection-induced pressure increase and cooling. During injection, the reservoir expansion caused by the pressure increase led to mechanical stress transfer through the reservoir, which prevented or delayed the reactivation of preexisting fractures. After injection stopped, there was an inversion of the mechanical stress transfers that favored shear reactivation, which may explain why microseismic activity occurred after the cessation of the injection. date: 2014 date_type: published publication: International Journal of Rock Mechanics and Mining Sciences volume: 72 publisher: Elsevier Science pagerange: 149-163 id_number: doi:10.1016/j.ijrmms.2014.09.005 issn: 1365-1609 official_url: http://doi.org/10.1016/j.ijrmms.2014.09.005 access_IS-EPOS: limited owner: Publisher citation: Jeanne, Pierre and Rutqvist, Jonny and Dobson, Patrick F. and Walters, Mark and Hartline, Craig and Garcia, Julio (2014) The impacts of mechanical stress transfers caused by hydromechanical and thermal processes on fault stability during hydraulic stimulation in a deep geothermal reservoir. International Journal of Rock Mechanics and Mining Sciences, 72. pp. 149-163. DOI: https://doi.org/10.1016/j.ijrmms.2014.09.005