Triaxial testing and hydraulic–mechanical modeling of sandstone reservoir rock in the Upper Rhine Graben

• Main Authors: Robert Egert, Robin Seithel, Thomas Kohl, Ingrid Stober
• Format: Article
• Language: English
• Published: SpringerOpen 2018-11-01
• Series: Geothermal Energy
• Subjects: Triaxial test; HM modeling; Mechanical characterization; Hydraulic implication; Buntsandstein; Upper Rhine Graben
• Online Access: http://link.springer.com/article/10.1186/s40517-018-0109-0

Abstract The Upper Rhine Graben (URG) is a highly favorable location for deep geothermal energy utilization. One of the main reservoir horizons is the lower Triassic Buntsandstein formation. While quantification of thermal and hydraulic parameters and their coupling is common, geomechanical factors are often neglected due to high costs and the expense in gathering data. Equivalent experiments with analog rocks, like triaxial tests, can help to improve this knowledge. Triaxial tests have been performed and evaluated on two different Buntsandstein rock examples as analogs to quantify the mechanical behavior under stress conditions found in the Buntsandstein of the URG. Both samples, Tennenbach (TenSst) and Pfinztal (PfSst) Sandstone, show high Young’s moduli under axial loading. With confining pressures up to 90 MPa, the axial failure strength is up to 448 (TenSst) and 561 (PfSst) MPa. The results demonstrate the usability of linear elasticity for the expected stress range in the Buntsandstein reservoir of the URG. The deformation behavior is described and a linear failure criterion is derived, predicting failure strength with a high accuracy. These experimental results can be further employed as calibration parameters for a hydro-mechanical evaluation of the deformation processes.