Research Projects

Contact person at RUB: Prof. Dr. Joerg Renner

In petrothermal geothermal reservoirs, hydraulic stimulation processes are used to create artificial fracture networks in the rock. These networks are the prerequisite for optimal heat exchange and geothermal energy extraction. The fracture formation in the stimulated rocks is associated with small-scale mechanical fracture processes that generate weak seismic signals. These induced microseismic events are used to track and control crack propagation in the subsurface. However, the relationship between the structural changes and the induced events is largely unresolved. Usually, there is no possibility to drill the deep-seated stimulated rocks and surface monitoring techniques do not reach the necessary resolution. However, the correct identification of the mechanical processes taking place is of great importance for predictions on the long-term operation of petrothermal geothermal reservoirs.

Within the framework of the joint project STIMTEC, hydraulic stimulation methods are to be optimized and further developed, and the hydromechanical processes occurring during hydraulic stimulation are to be characterized. It is planned to investigate the formation and propagation of hydraulic pathways under known boundary conditions in field tests. For this purpose, boreholes will be drilled in an experimental mine and used for controlled stimulation tests. Following the tests, validation boreholes are planned to verify the effects of the stimulation. The tests will be accompanied by hydraulic pumping tests, laboratory experiments, high-resolution seismic monitoring and numerical modeling. Subsequent drilling of a stimulated area will for the first time provide unambiguous evidence of the hydromechanical processes taking place as well as the associated seismic and hydraulic fingerprints.

STIMTEC is divided into five subprojects with a total of seven work packages. After geological and structural exploration, several boreholes will be drilled in a selected section of the mine. Pumping tests will be used to determine the initial hydraulic parameters of the boreholes. Furthermore, a monitoring network will be set up to record seismic and acoustic signals during the stimulation.After completion of the stimulation experiments, so-called validation wells will be drilled and pumping tests will be carried out again in order to narrow down the hydromechanical processes and to assign the corresponding diagnostic phenomena.  The work is accompanied by laboratory experiments and numerical simulations. The possibility to investigate a rock package directly after hydraulic stimulation for the first time allows us to expect a considerable gain in knowledge about stimulation processes on a field scale. The result should be a concept for the optimized implementation and monitoring of hydraulic stimulation measures.

To the STIMTEC Website

Coordinators of the Subprojects: Prof. Dr. Joerg Renner, Prof. Dr.-Ing. Arne Roettger

Wear and the associated service life of tools are counteracting the efficiency of tunneling processes. Till today an insufficient knowledge about the acting wear mechanisms and the interactions between the ground to be excavated and the tunneling tools are given. Based on this circumstance, no reliably predictions about the wear condition and the remaining service time of tunneling tools can be obtained. It is the aim of C5 to describe the complex tribological system of tunneling tools in soil and soft rock. In addition, tool-ground interaction is being thoroughly investigated so that crack initiation, crack propagation and ultimately ground degradation can be fundamentally understood. Thus, in subproject C5, geophysical investigations of rock-fragmentation and examinations of the tool wear from a materials technology perspective will go hand in hand, so that the entire tribosystem can be considered and understand comprehensively and interdisciplinary. Furthermore, subproject C5 intensively interacts with the subprojects C4 and C6. Thereby, C4 and C6 are focusing on numerical methods and questions with respect to fragmentation of the ground and the wear of the tools. Subproject C5 will support both numerical projects by providing input data as well as by validating the calculations by experimental tests.

To the SFB 837 Website

PI: Dr. Marieke Rempe
Project duration: 01/19 - 12/21

In this DFG-funded project, we explore the kinetics of processes that govern the alteration and deformation of pseudotachylytes and associated microstructural characteristics to quantify the likelihood of their preservation and recognition by combining laboratory and field investigations. We are conducting high-temperature, high-pressure alteration and deformation experiments on natural pseudotachylytes and synthetic analogue materials representing a range of generation scenarios and alteration stages. The experiments will provide diagnostic features against which we will compare microstructures of natural fault-generated pseudotachylytes collected in the field to evaluate their alteration history. As fault-generated pseudotachylyte, a type of fault rock that preserves evidence of frictional melting, appears to be relatively rare considering the frequency of earthquakes and commonly accepted source models that predict melting conditions to be coseismically reached for large crustal earthquakes, the proposed study will provide answers to the pressing question whether pseudotachylytes are in fact rarely generated or rarely preserved in a recognizable form. Answering this question is a mandatory prerequisite to fully exploit the field record for the derivation of earthquake-source parameters and the properties of fault rocks at depths. Complementary to seismological analyses of recent earthquakes, the proposed experiments and microstructural work will provide independent constraints on the energy budget of earthquakes.

Contact person for the subproject: Dr. Ralf Dohmen, Prof. Dr. Joerg Renner

Carbonates are arguably the most important rock type for reconstructing Earth system evolution with respect to the physical and chemical evolution of the oceans, as well as changes in atmospheric composition and global climate. The evolution of the climatic and physico-chemical parameters on Earth's continents and in the oceans throughout the Phanerozoic can be inferred by analysing marine and continental carbonate archive proxies including the geochemistry, fabrics, and mineralogy of these deposits. All carbonates are subject to variable degrees of post-depositional/post-mortem alteration, often commencing at a very early stage and continuing into the deep burial and anchimetamorphic domain.

Diagenesis, i.e. the overprint of environmental and metabolic signatures, represents the single most significant obstacle in deep-time carbonate archive research. Moreover, the interpretation of individual proxy data sets from carbonate archives requires a detailed understanding on the distribution behaviour of elements and isotopes during the formation of biogenic, abiogenic and organomineralic calcium carbonate.

In Phase II of the CHARON research project, we move from calibration of our tools to application using a wide range of experimental and natural carbonate materials. Among others, examples of our research include corals and their earliest diagenesis, the early diagenetic microbe-sediment interaction in shallow marine cores, patterns in the crystallography and material properties of diagenetically altered biogenic carbonates as well as limestone-to-dolostone transition zones. Similar to Phase I, a wide range of traditional and non-traditional geochemical proxies are applied to test the resilience to diagenetic overprint for various carbonate mineral archives.

To the CHARON Webpage

PI: Prof. Dr. Jörg Renner

The SHynergie project consists of a total of six subprojects:

• Experimental investigation and hydro-mechanical modeling of the propagation mechanisms of stimulation-induced cracks.
• Development of the storage capacity of fractures and shear cracks under the influence of solution-precipitation processes
• Propagation of elastic waves in hydro-mechanically damaged media
• Frequency dependence of poro-elastic properties of fractured rocks
• Cross-scale modeling of inelastic processes in hydraulic stimulation
• Tool development for representing the mind of an ideal expert

Hydraulic stimulation is the primary means of developing subsurface reservoirs in terms of the extent of fluid transport. The associated creation or enhancement of a hydraulic conduit system involves a number of hydraulic and mechanical processes, but chemical reactions such as dissolution and precipitation can also affect the stimulation outcome on time scales of only a few hours. Given the scale and complexity of these processes, the control potential for those operating a stimulation depends critically on the ability to integrate maximum site-specific information with a deep understanding of the process and a wide range of experience.

Various subprojects

• Rheology of eclogitic rocks (Prof. Dr. Joerg Renner, Prof. Dr. Bernhard Stoeckhert)
• Particle size distribution of hydrous silicate melts and viscous compaction of partially molten aggregates (Prof. Dr. Joerg Renner)
• Fluid transport in and frictional strength of fractured and fractured rocks (Prof. Dr.-Ing. Joern Mosler, Prof. Dr. Joerg Renner)
• Microstructure evolution in peridotites during deformation at high stresses and subsequent recrystallization at decreasing stresses - experiment and nature (Prof. Dr. Joerg Renner, Prof. Dr. Bernhard Stoeckhert, Prof. Dr. Claudia Trepmann)
• The influence of mechanical stress on transport processes at interfaces (Prof. Dr. Klaus Hackl, Prof. Dr. Joerg Renner)
• The microstructural evolution of polycrystalline aggregates during high temperature deformation: numerical modeling taking into account experimental observations (Prof. Dr. Klaus Hackl, Prof. Dr. Joerg Renner)

PI: Dr. Yuval Boneh
Partner at the RUB: Dr. Sarah Incel, Prof. Dr. Joerg Renner

As the subducted slab penetrates the Earth’ mantle, its crustal layer experiences intensive shearing with regions where the slab is coupled and decoupled from the overriding plate in a way that affects the regional seismicity, the distribution of volcanism, and the dynamics of the subducted slab. During subduction the crustal layer of the subducted slab will be sheared due to the resistant frictional force between the subducted slab and the overriding plate. Often it is an oceanic slab that is subducted with a typical basaltic oceanic crust. At the increased pressure conditions, subduction may change its mineralogical composition (i.e., metamorphose) into a rock called amphibolite, mainly comprised of the minerals amphibole and plagioclase. One of the most common features of naturally deformed amphibolites is their strong foliated texture (also seen in the figure), which can significantly affect the strength of amphibole rocks, as widely seen in other anisotropic minerals. The experiments done by Dr. Boneh and Dr. Incel at RUB Rock Deformation lab will use a natural sample with a strong pre-existing texture to simulate the unique conditions and mechanical anisotropy of a subducting slab with implications for subduction zone dynamics and seismic potential.  

PI: Dr. Anna Rogowitz, University of Vienna
Project partners at the RUB: Dr. Sarah Incel, Prof. Dr. Joerg Renner

The rheological behaviour of rocks is directly reflected by the formation of tectonic structures like folds, boudins or shear zones and is one of the main controlling factors of deformation at the plate boundaries and interiors. Besides temperature the rheological behaviour of a rock is largely controlled by the relative amount, distribution and strength of its minerals.

In this project we will study the rheological behaviour and microstructural evolution of eclogites composed of omphacite and garnet in varying fractions and in different strain, strain rate, pressure and temperature conditions. Owing the formation and presence of potentially large amounts of eclogite their deformation behaviour is of great importance for the rheology of the lithosphere in continental collision and subduction zones. The investigations will be based on triaxial deformation tests at high temperature and high pressure conditions characteristic for in-situ conditions at plate boundaries. The samples will be synthesized in a piston cylinder apparatus to control the relative proportions of omphacite and garnet. Rheological laws for eclogites of different compositions in different regimes will be determined suitable for large scale modelling. Additionally detailed microfabric analysis of experimentally and naturally deformed eclogites from the Type-locality (Koralpe and Saualpe, Austria) will be performed using optical microscopy and high resolution techniques (scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy). By comparing experimental microstructures and associated deformation mechanisms to natural ones we will get information on deformation conditions and mechanisms of the natural deformed eclogites.

The results of this study will provide important constraints for our understanding of the rheology and deformation behaviour of eclogites, and thus improve the understanding of processes at greater depths in subduction and collision zones. Additionally crucial insights for the behaviour of two-phase rocks will be gained.

To the Webpage of the University of Vienna