European Geothermal PhD Days 27-29 April 2022

3D geological modeling has become an imperative tool to contribute to studies of geothermal exploration and production over the last few decades. It has been applied and is still in progress with the cooperation of geological and geophysical excursions, leading to solutions for structurally complex settings in geothermal operations and developments. New, interesting opportunities and application domains are emerging, challenging geomodellers to integrate data and improve methodologies from a variety of sources (e.g., remote-sensed and subsurface data) and addressing integrated data. Therefore, this meeting is encouraging contributions in 3D-geological modeling for the improvement of geothermal applications.

Geophysical methods play an important role in geothermal exploration and contribute to the initial characterization of the system. New developments in the areas of joint inversion of geophysical methods have led to significant amounts of research applied to geothermal characterization. Advances in geological modeling have also contributed substantially to the quality of prior information used for geophysical interpretation. Additionally, developments in geophysical equipment, such as resistant downhole sensors and higher resolution systems have opened new avenues for geothermal research.

In this session we feature abstracts that use geophysical methods to better characterize geothermal systems in different geological settings with a special focus on different independent and joint inversion approaches.

Monitoring of geological quantities in (Enhanced) Geothermal Reservoirs is key for both safety and efficiency of geothermal operations. This session features diverse contributions and case studies concerned with the application of novel methods and technologies involved in the monitoring process of geothermal systems. A special focus will be put on real-world monitoring applications and on advances and burdens of joint-inversion approaches in multi physics setups.

Successful management and improvement of a geothermal energy system requires a holistic approach dealing with all the different components in the reservoir and the power plant. With regards to the reservoir, monitoring changes in temperature, pressure and formation stresses, movements of cold fronts and changes in geochemistry all play a crucial role in maintaining the reservoir health and integrity. Concerning the power plant, advances in plant technology are desirable not only to improve efficiency, reliability and safety of operations but to expand the viability envelope to lower temperatures as well. Abstracts regarding the reservoir management and power plant design and optimisation are called for improving the performance and reliability of future geothermal energy systems.

Reinjection is a key process that partly controls the success of geothermal projects. It can benefit to waste water disposal, reservoir pressure maintenance and supplement of heat carrier. Maintaining and enhancing the injectivity are thus of great importance. However, the injectivity is sensitive to various operations. For example, the silica scaling which forms in the reservoir during reinjection can decrease the injectivity. To maintain the injectivity and sustain the geothermal projects, mechanisms contributing to decrease in injectivity are expected to be figured out. In addition, various stimulation techniques have been used to enhance the injectivity, such as hydraulic fracturing and thermal stimulation. How these techniques contribute to increasing injectivity of the geothermal reservoirs, especially the fractured geothermal reservoir, is of great significance for designing and managing the projects. With this respect, abstracts regarding experimental and numerical works on maintaining and enhancing the injectivity of geothermal reservoirs are welcome.

Geothermal reservoirs are complex, underground systems that can be found under a wide range of geologic and thermodynamic conditions. As such, geothermal systems can exhibit different properties in terms of their mineral composition, structural style, and fluid geochemistry, among others. During geothermal operations, various rock-fluid interactions occur, along with chemical reactions between brines and injected fluids. These processes, namely fluid mixing, mineral precipitation, dissolution, and phase separation are observed when the initial equilibrium in the reservoir is disturbed. Such hydrogeochemical reactions often introduce uncertainty in regards to the way the reservoir will perform--both in the short and long term-- as they have a direct effect on the amount of thermal power we can extract from a geothermal system and its evolution over time. Additionally, renewed (supplementary) interest in geothermal fluids has arisen recently due to the occasional high presence of rare chemical constituents such as lithium, zinc, lead, rare earth minerals, etc. that can be co-produced along with geothermal energy. Understanding the role that geochemistry and fluid-mineral equilibria have to play in these systems is of key importance to ensure the efficiency, technical viability, and profitability of geothermal energy worldwide. In this session, we are looking for abstracts that aim to understand the role of geochemistry and profitability of hydrogeochemical processes to geothermal energy.

Geothermal exploration has the priority over gas and oil exploration for a number of reasons, being environmentally friendly, renewable and sustainable, its low cost and high efficiency. Among other challenging parameters of geothermal exploitation, sustaining its efficiency and safety stands out as the major concern. In that sense, reducing the risks of failure in its multi-phased procedures necessitates making reliable estimates of risks and costs of the project in hand. One of the adopted scientific approaches is the quantification of uncertainties of in-situ subsurface structural properties and heterogeneity parameters of the reservoir bodies such as temperature, pressure, porosity, permeability, etc. By gaining knowledge from these quantifications, more reliable decisions can be made for the pre- and post- geothermal operations like targeting the drilling fields, increasing the accuracy of hydro-geo-mechanical tests and establishing enhanced geothermal systems. Within this respect, abstracts regarding uncertainty quantification and risk & cost estimations are called to contribute to geoenergy systems for future.

Geothermal systems occur in different geological configurations where the complexity of their systems requires detailed analysis of the reservoir and the geological properties that allow an adequate understanding of them. The importance of these studies was associated with the study of factors that control the flow of liquid associated with primary / secondary porosities to estimating the dimensions or geomechanical properties of the rocks, among others. The presented section will cover approaches in quantitative assessment of geological, geophysical and geomechanical properties for an integrated reservoir model as well as highlighting the understanding of different topics within structural analysis such as fault, deformation, stress, etc.. The other section is in charge of the characterization of thermal, hydraulic, mechanical and chemical processes in a geothermal reservoir.

Understanding injection-related seismicity caused by the operation of geothermal power plants is a key challenge for running such plants efficiently and safely. It has been shown that geothermal and volcanic systems are frequently linked to higher levels of natural and/or induced microseismic activity. Accurate interpretation of source mechanisms combined with high-resolution hypocenter locations can potentially lead to a better understanding of the reservoir boundaries, location of fractures or faults, and track the migration of the injected fluids. Furthermore, advanced seismic monitoring techniques are required to prevent inducing large earthquakes that may jeopardize wellbore stability and/or damage surface infrastructure.

In this session, we invite contributions that seek a deeper understanding of induced and triggered seismicity related to the operation of geothermal power plants. We particularly encourage novel contributions on seismic monitoring techniques as well as microseismic-source characterization. We also welcome research on traffic-light systems for decision making during the injection and extraction of geothermal fluids.