Hannes Krietsch

TL;DR: The In situ Stimulation and Circulation (ISC) experiment at the Grimsel Test Site in Switzerland as discussed by the authors was designed to address open research questions in a naturally fractured and faulted crystalline rock mass, and two hydraulic injection phases were executed to enhance the permeability of the rock mass.

TL;DR: In this paper, the authors present the rationale, concepts and initial results of stimulation experiments in two underground laboratories in the crystalline rocks of the Swiss Alps, where a first experiment series at the 10 m scale was completed in 2017 at the Grimsel Test Site, GTS, and the Bedretto Underground Laboratory for Geoenergies, BULG, are planned to be at the 100 m scale, closer to conditions of actual EGS projects, and a step closer towards combining fundamental process-oriented research with testing techniques proposed by industry partners.

TL;DR: In this paper, an extensive campaign to characterize rock stresses on the decameter scale was carried out in three 18-24m long boreholes drilled from a tunnel in foliated granite at the Grimsel Test Site, Switzerland.

TL;DR: In this article, a series of hydrofracturing and overcoring tests were performed to characterize the stress field at the Grimsel Test Site (GTS) underground rock laboratory, and the fracture growth direction from microseismicity is consistent with the principal stress orientations from the overcoring stress tests, provided that an anisotropic elastic model for the rock mass is used in the data inversions.

TL;DR: In the framework of a hydraulic stimulation experiment in crystalline rock at the Grimsel Test Site, a deterministic 3D geological analog is compiled that may serve as a decameter-scale analog of crystalline basement rocks, which is often targeted for enhanced geothermal systems.