Subproject No 3
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Propagation of elastic waves in hydro mechanically damaged media

Doctorate Researchers: Thomas Möller, Nele Pollmann
Principal Investigators: Wolfgang Friederich, Holger Steeb

Deep geothermal reservoirs consist of rocks with systems of joints or fractures. They exhibit networks of high-aspect-ratio geometries. Motivated by this peculiar geometry, the hydro-mechanically coupled processes are modeled using a hybrid-dimensional modeling approach (HDA). Furthermore, the simulation of wave propagation in such media is performed by means of a nodal discontinuous- Galerkin-approach (NDG).

Quasi-static poroelastic equations are combined with a dimensional reduced Poiseuille-type flow between parallel plates . The simulations show that two main processes occur for simple fracture networks, fracture flow within and between the connected fractures and leak-off from the fractures to the surrounding rock (c.f. Fig 1) . The aim is the implementation of natural fracture systems, i.e. three dimensional hydro-mechanically coupled processes within complex systems of fractures (c.f. Fig 2).

The existing NDG software for the simulation in homogenous and isotropic media will be expanded using the concept of linear slip interfaces developed by Schoenberg (1980). The NDG method uses numerical fluxes at the element boundaries to calculate the propagationas well as boundary conditions. These fluxes will be modified by the interface condition to include fractures as well as fracture networks in the simulation. Fig. 3 shows a one-dimensional wave propagation over one interface.

The general aim is to replicate typical seismic surveys to study the effect of fracture networks. Thus, typical seismic attributes will be provided by numerical investigations. Additionally the effect of these networks should be examined on the localisation of induced quakes. The modeling will improve the current methods with regard to structural exploration and will be able to predict seismicity induced by stimulation processes.

Conference Proceedings

Conference Date Title Author
5th GACM Colloquium on Computational Mechanics, TUHH, Germany September 30-Oktober 1, 2013 Numerical Homogenization of Interlayer Flow Processes Nele Pollmann, Ralf Jänicke, Holger Steeb
85th Annual Meeting of GAMM hosted by FAU , Germany March 10-14, 2014 Consolidation of a poroelastic sphere: Numerical investigations of Cryer’s problem Nele Pollmann, Holger Steeb
10th Euroconference on Rock Physics and Rock Mechanics, Aussois, France May 10-15 2014 Consolidation in spherical domains: A time and frequency domain analysis Nele Pollmann, Holger Steeb
6th European Geothermal PhD Day, Delft, The Netherlands February 25–27 2015 On the hydro-mechanical properties of fluid flow through fractured rock: A 3-dimensional hybrid-dimensional approach Nele Pollmann, Carlo Vinci, Jörg Renner, Holger Steeb
75. Jahrestagung der DGG, Hannover, Germany March 23-26 2015 Numerical Simulation of Seismic Wave Propagation in Fractured Media Thomas Möller, Wolfgang Friederich