Modellung permeability an simulation for deep heat mining

Permeability is the decisive rock property that determines whether or not geothermal energy in non- volcanic areas such as Central Europe can be generated at significant levels, including electricity production. In addition, permeability is a fundamental control on heat and mass transfer during geologic processes in the Earths crust. At the depth of deep geothermal reservoirs (>4 km) permeability is bound to fractures and typically too low for geothermal operations. There is currently no quantitative theory for the permeability of fractured rock masses at these depths and how it depends on factors such as rock type, regional and local stress, temperature and depth or whether it can sufficiently be enhanced by the technique of hydraulic stimulation. The lack in understanding fracture permeability is the most crucial and fundamental scientific problem for determining if geothermal electricity generation is an option in countries such as Switzerland and Austria. It stems from the fact that it is basically impossible to make sufficiently comprehensive and detailed, quantitative observations and measurements of it in situ. Numerical simulation is a key tool to close these knowledge gaps. Current commercial and academic simulation codes are insufficient to provide the level of rigor and computational efficiency needed to perform research on fracture permeability of large, complex systems. Our project Modelling permeability and stimulation for deep heat mining integrates the experience and complementary expertise of four internationally leading groups in reservoir engineering, geothermal fluid flow simulation, numerical mathematics and geomechanical modeling, respectively. Together, we will implement the next generation of numerical simulation tools to address the fundamental scientific questions of complex fractured reservoirs outlined above and to explore their impact on geothermal energy operations. The four collaborative subprojects will Advance the functionality of the CSMP++ simulation platform that can rigorously simulate a wide range of component physics on geometrically complex (i.e., geologically realistic) reservoir representations in the form of discrete fracture and matrix models (Subprojects A and B, led by Prof. Dr. Stephan Matthai, MU Leoben, and Dr. Thomas Driesner, ETH Zurich). Develop cutting edge algorithmic and high performance computing (HPC) methods (Subproject C, led by Prof. Dr. Rolf Krause, Universita della Svizzera italiana, Lugano) for simulating shearing and other mechanical processes on rough fracture surfaces. Combining this functionality with the CSMP++ code will allow the simulation of the complex interactions of fracture mechanics and fluid circulation scenarios on the highest technical level currently possible. Develop a complementary modeling approach that is continuum-based but employs extremely fast, GPU-accelerated simulation methods (Subproject D, led by Prof. Dr. Stephen Miller, University of Neuchatel). Mutual benchmarking and comparison with subprojects A to C will explore the potential of this approach as a fast but sufficiently reliable tool that can be run on normal computers for future near real-time application in actual projects. In subprojects A, B, and D the new simulation tools will then be used for research (A) to quantify the influence of hydraulically induced shearing and other mechanical and material parameters on the permeability of fractured reservoir rocks, (B) to characterize the controls that complex fracture networks exert on heat extraction by circulating fluids, and (D) to approximate the evolution, growth, and coalescence of fracture networks associated with the injection of fluids when developing an enhanced geothermal system (EGS).