Comparison of Hydro-Mechanical Coupled Numerical Simulations with ThermoTriaxial Lab Investigations

Sebastian Weinert1, Wolfram Rühaak2, Kristian Bär1, Ingo Sass1
1 Technische Universität Darmstadt, Fachgebiet Angewandte Geothermie, Schnittspahn Str. 9, 64287 Darmstadt
2 Technische Universität Darmstadt, Darmstädter Exzellenz Graduiertenschule für Energiewissenschaft und Energietechnik, Jovanka-Bontschits-Straße 2, 64287 Darmstadt

P 5.7 in Deep geothermal reservoirs - synergies and conflicts

 

 

The impact of changing fluid pressure on rocks can be described by hydro-mechanical coupling (HMC) and is of special relevance for deep geo reservoirs. HMC can be segmented into fluid-to-structure and structure-to-fluid processes (e.g. Rühaak et al., 2014). For validation of a newly developed HMC FEM code a comparison with laboratory results was performed.

A test series of Fontainebleau sandstone was conducted in a thermo triaxial device (ThermoTriax). Using the ThermoTriax fluid-structural interactions can be simulated and evaluated in a laborative scale. Prepared Fontainebleau sandstone cores were mounted and saturated in the triaxial cell. By increasing the vertical stress (structure-to-fluid), the discharge of pore fluid is quantified using two volume pressure controllers (VPCs) connected to the triaxial cell.

Vice versa, for an evaluation of the fluid-to-structure effect the pore pressure was increased in a second test series of the same sandstone specimens. By applying the same, unaltered pressure conditions for σ1 and σ3, the vertical displacement, and therefore the expansion of the specimen, can be measured.

In addition to the hydraulic and mechanical coupling, the temperature effect was added to the existing model. A second benchmarking of the model and the included temperature effect is planned to be conducted in the ThermoTriax for temperatures up to 165°C.



 

 

Rühaak, W.; Bense, V. F.; Sass, I. (2014): 3D hydro-mechanically coupled groundwater flow modeling of Pleistocence glaciation effects. In Computers & Geosciences, 67 pp. 89-99.