Conference Agenda

Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).

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Session Overview
11.2-1 Approaches to Sustainably Develop the Subsurface Potential for Storage and Disposal
Tuesday, 21/Sept/2021:
9:00am - 10:30am

Session Chair: Max Wippich, DEEP.KBB GmbH
Session Chair: Till Popp, Institut für Gebirgsmechanik GmbH

Session Abstract

To accomplish the energy transition, new methodologies and technical solutions for the storage of renewable energies need to be developed. A fundamental challenge lies in the fact that energy production from renewable sources (wind or sun) is subject to fluctuations that do not match the daily and/or seasonal swings of energy demand. Furthermore, the safe long-term disposal of environmentally hazardous nuclear and toxic waste in geological repositories is a social responsibility.With salt caverns and porous reservoirs, the subsurface offers a great potential for the storage of energy carriers (e.g. hydrogen, synthetic methane), potential energy (compressed energy) or thermal energy. Regardless of the time scale (daily seasonal or even over periods of up to 1 million years), barrier formations like salt, clay or crystalline rock ensure the necessary integrity and safety.This session aims to connect research, technical concepts and case studies addressing the geological boundary conditions of the various storage and repository options. The range of topics involve the description and assessment of the properties of storage and barrier formations and the relevant processes that occur during the operation and post-operation/abandonment phases of storages and repositories. These include the development of exploration methods, laboratory investigations to characterise rock properties at various scales, and the modelling-based analyses and simulations of coupled thermal, hydraulic, mechanical and (geo)chemical processes. An elementary part of these efforts is the incorporation of experience gained over the past decades to validate the models and methods used, as well as the linking of different scales of magnitude.

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9:00am - 9:30am
Session Keynote

Storage in the energy transition: A regulator perspective

Wouter van der Zee

State Supervision of Mines, Netherlands, The

The underground storage will play an important role in the energy transition, both for energy storage as for CCS. Current storage activities in the Netherlands are for natural gas, diesel oil and nitrogen are in both in depleted gas reservoirs and salt caverns. These probably will be extended in the near future with storage of CO2, hydrogen and compressed air.

The Dutch State Supervision of Mines is the regulator who oversees that these activities are performed in such a way that they are safe, now and in the future. This means that the full life cycle has to be considered with a broad perspective on the safety of people and the environment.

The predictions of behaviour of the storage and its fluids and related risk will have large uncertainties due to the level of uncertainty in the subsurface data used, and the limited amount of data to calibrate the models which calculate the risk. In most cases this will mean that the risk can’t be calculated probabilistically. In that case for decision making it is necessary to not only investigate the most likely scenario, but to the range of realistic, possible scenarios to identify the real risk. The period after storage will be orders magnitudes longer than the storage activity itself. This will lead to even larger uncertainties for this phase.

We have to face the fact that we can only partly reduce this uncertainty by further research and monitoring. However research and monitoring can help us to quantify the uncertainty. This emphasizes the importance that operators, policy makers and regulators are able to handle the uncertainties in their decisions before, during and after the storage activities, and communicate openly about them.

9:30am - 9:45am

Sustainability in energy storages - How modern geoscience concepts can improve underground storage monitoring

Benjamin Haske, Tobias Rudolph, Bodo Bernsdorf

Technische Hochschule Georg Agricola, Germany

Re-using of large-volume salt caverns for the intermediate storage of liquid and gaseous energy carriers is an indispensable step on the way to a sustainable energy economy. Continuous development of methods for monitoring these facilities is a crucial part of the social license to operate. In the research project "Monitoring system for the safety of cavern storage facilities using satellite and unmanned aerial system (UAS) data" (KaMonSys), safety solutions for critical infrastructures are implemented in an interdisciplinary approach of remote sensing and geoscientific methods. Using underground storage facilities (USF) as an example, multisensory approaches are being developed to monitor the facilities as well as their surroundings by satellite and UAS-based monitoring to detect possible emissions, such as methane, hydrogen and carbon dioxide.

The coupling of classical geological methods of subsurface assessment with innovative approaches from remote sensing shows a huge potential for further research. Although KaMonSys will initially be developed for a cavern storage facility, which have considerable relevance for the "in time" gas supply of Germany, the final process will also be applicable to other industries as a safety solution for secondary markets.

This presentation describes the initial evaluation of available spatial data (INSPIRE and associated project partners Uniper and Salzgewinnungsgesellschaft Westfalen) on the surface/Subsurface situation, the integrated development of a 3D geoinformation system (GIS) to evaluate data and its usage for the development of 3D UAS flight plans.

The project is supported by federal funds within the German BMBF funding framework "Research for Civil Security" (FKZ 13N15366).

9:45am - 10:00am

Large Scale Experiments on the Tightness of Boreholes under Cyclic Loading

Marcel Schulz, Birgit Müller, Frank Schilling

Karlsruhe Institute of Technology, Germany

The transition from nuclear and fossil energy to renewable energy leads to higher fluctuations in energy supply – but storage for power is negligible so far. In underground gas storages (UGS) huge amounts of TWh can be stored to meet the demand consistently. However, this results in increasing injection and extraction frequencies, leading to faster pressure and stress changes and therefore posing additional challenges for reservoir rock, cap rock and technical components.

To evaluate the effects of additional cyclic loading on the rock-cement-steel-compound of the UGS infrastructure, we use an autoclave system on a realistic scale. Mainly abandoned drillings are simulated, the system therefore consists of a 2 m long cemented steel casing with an autoclave chamber at each end and surrounding heating mats. To simulate injection and extraction, gas pressure (N2) is applied and released on both ends. Additionally, temperature can be raised to 100 °C. Between loading cycles, permeability can be measured to determine the effect of pressure and temperature variation on the tightness of the system.

We present results from the analysis of three cemented casings. Since the hardened cement isn’t connected to the steel casing after experiments, we assume an annular gap as main gas path. This gap is modelled and fitted to the experimental data. After pressure variations between 0 bar and 60 bar, tightness of the system decreased in every experiment, which leads to an increased modelled annular gap width. Temperature variations between 30 °C and 70 °C tend to increased tightness slightly.

10:00am - 10:15am

Nachweis der Integrität von Salzkavernen zur hoch-frequenten zyklischen Gasspeicherung

Tobias Fabig, Till Popp, Sebastian Knöfel

IfG Leipzig GmbH, Germany

Untertage-Gasspeicherung stellt eine wesentliche Nutzung des Untergrunds dar. Sie trägt insbesondere zur Stabilität der Energieversorgung bei. Auch in Zukunft kommt der geologischen Kurz- und Langzeitspeicherung stofflicher Energieträger eine große Rolle zu.

Obwohl die Gasspeicherung in Salzkavernen Stand der Technik ist, haben sich die Betreiberanforderungen dahin gehend geändert, dass neben den saisonalen Gasumschlägen zunehmend auch kurzfristige hoch-frequente Speicherzyklen aufgrund veränderter Speichermarktanforderungen gefahren werden. Insbesondere aufgrund der thermo-mechanischen Wechselwirkung beim Ein- und Ausspeichern von Gas resultieren daraus grundlegend neue Fragen zur Betriebssicherheit, d. h. Integrität der geologischen Barriere Salz sowie der technischen Installation des Bohrloch-Casings im Kontakt mit der Bohrlochzementierung sowie dem Salzgebirge.

Unter der Zielstellung einer qualifizierten Bewertung potentieller Risiken bei den verschiedenen Varianten des modernen Speicherbetriebes wurde durch das IfG im Rahmen des BMBF-Forschungsvorhabens SUBI eine umfassende Studie zu den verschiedenen Aspekten durchgeführt.

Ausgehend von einer umfassenden Literaturstudie zum nationalen und internationalen Stand der Fluidspeicherung in Kavernen in Salzgesteinen wurden die aktuellen technischen Konzepte dargestellt und stattgefundene technische Havarien ausgewertet. Die daraus resultierende Arbeitsthese ist, dass bei den in der Literatur beschriebenen Havarien kein integrales Versagen der Salzbarriere stattfand, sondern generell technische (z.B. schlechte Zementation) oder geologisch/geomechanische Bohrloch-Casing-Probleme (z.B. Strukturrandlage, ungünstige Salzbedingungen, Überlagerungen im komplexen Kavernenfeld) ursächlich waren.

Zur Verifizierung dieser Thesen wurden sowohl experimentelle Untersuchungen an natürlichen Salzgroßproben und Bohrlochzement als auch modelltechnische Arbeiten zur Modellierung von zyklisch überprägten saisonalen Belastungen bei der Gasspeicherung in Salzkavernen durchgeführt.

10:15am - 10:30am

The SpannEnD project – Towards a robust prediction of the 3D stress state in the upper crust of Germany

Karsten Reiter1, Steffen Ahlers1, Sophia Morawietz2, Luisa Röckel3, Tobias Hergert1, Andreas Henk1, Birgit Müller3, Oliver Heidbach2

1TU Darmstadt, Institute of Applied Geosciences, Schnittspahnstraße 9, 64287 Darmstadt, Germany; 2Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany; 3Karlsruhe Institute of Technology, Institute of Applied Geosciences, Kaiserstraße 12, 76131 Karlsruhe, Germany

The assessment of the long-term stability of geological units in the context of subsurface use is a complex topic in which various geoscientific and technical aspects play an important role. For example, the geomechanical stability of radioactive waste repositories due to endogenous, exogenous and engineering processes is an important aspect in the long term. For a stability prognosis, an estimation of the recent stress state as well as an assessment of realistic future stress changes is required. However, data on the current stress state in the upper crust are incomplete, sparse and spatially unevenly distributed. Therefore, geomechanical-numerical models are the only possibility to estimate the complete stress tensor at locations where stress observations are not available.

The SpannEnD project, had the goal to estimate the 3-D stress state in Germany. Therefore, a simplified subsurface model was created. Since stress data are essential for the calibration procedure, the first open access database for stress orientations as well as stress magnitudes was developed, which mainly summarises data from the study region. The best-fit stress model is assigned to the model which reproduces the results of many of the available magnitudes of horizontal stresses well. In the model region, there are numerous large-scale faults or fault systems that have an influence on the local stress state. However, the large number of faults could not be implemented as structural features in the geomechanical model. However, the modelled stresses are applied on the fault geometries to assess the fault reactivation potential.

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