Stress-based tomography: potential, open-questions and future developments

Abstract

Fracture network characterization is critical for many subsurface engineering problems in petroleum, mining, nuclear waste disposal and Enhanced Geothermal Systems (EGS). Due to limited exposure, direct measurement of fracture network properties at great depth is not possible and geophysical imaging techniques cannot resolve the fractures. Therefore, tomographic imaging techniques have been proposed and applied to reconstruct the structural discontinuities of rock mass. Stress-based tomography is a novel concept aiming at probabilistic imaging of the fracture network using the stress perturbations along deep boreholes. Currently, this approach has only been successfully tested on two-dimensional fracture networks. However, its great potential to unravel the heterogeneous structure of fractured rocks at great depth motivates further scientific effort. Here, we present the potential, open questions, current challenges and necessary future developments in order to apply this methodology to image three-dimensional multiscale structure of the rock mass in the field. Other tomographic approaches such as tracer and hydraulic tomography invert tracer breakthrough curves (BTCs) and pressure response in an observational well. We suggest a joint and comparative tomographic analysis in a Bayesian inversion framework to reconstruct Discrete Fracture Networks (DFN). This is expected to provide a new view of the strengths of each tomographic variant.

Authors 5

1. Peter Bayer corresponding

   Martin Luther University Halle-Wittenberg

   Affiliation as printed

   Applied Geology, University of Halle, Halle (Saale), Germany (peter.bayer@geo.uni-halle.de)

2. Mohammad Javad Afshari Moein

   Martin Luther University Halle-Wittenberg

   Affiliation as printed

   Applied Geology, University of Halle, Halle (Saale), Germany (peter.bayer@geo.uni-halle.de)

3. Márk Somogyvári corresponding

   Technische Universität Berlin

   Affiliation as printed

   Technical University of Berlin, Institut für Angewandte Geowissenschaften, Berlin, Germany

4. Lisa Maria Ringel corresponding

   Martin Luther University Halle-Wittenberg

   Affiliation as printed

   Applied Geology, University of Halle, Halle (Saale), Germany (peter.bayer@geo.uni-halle.de)

5. Mohammadreza Jalali corresponding Aachen Chair for Engineering Geology and Hydrogeology

   RWTH Aachen University

   Affiliation as printed

   Chair for Engineering Geology and Hydrogeology, RWTH Aachen, Aachen, Germany