The Cheb Basin (Czech Republic) as a Potential Natural Analogue Site for Geological Carbon Storage - Past, Current and Planned Activities
Abstract
General difficulties for evaluating methods for the detection and monitoring of CO2 spreading and degassing to the atmosphere induced by CO2 sequestration are the time scale of transport processes and the desired situation of a non-release of sequestered CO2 from the subsurface. The unique structures of the Cheb Basin (western Eger rift / Czech Republic) provide excellent opportunities for further direct investigations of transport processes along migration paths caused by cap rock failures and the development and validation of adequate monitoring tools. The Eger rift belongs to the European Cenozoic rift system and represents an approximately 50 km wide and 300 km long ENE-WSW striking continental rift that formed during the Upper Cretaceous-Tertiary transition. This rift zone is one of the most active seismic regions in Central Europe. This rift zone is one of the most active seismic regions in Central Europe. There are a lot of gas emanations (cold vents) with high CO2 contents (> 99 vol% CO2). The CO2-fluxes vary in a wide range between smaller than 1 up to 4000 L/h per vent. The degassing activity is assumed to be generally connected to the seismic activity, which has mainly a swarm-like character, and is originated in the upper mantle. Comprehensive studies of CO2-rich fluids have been started 20 years ago and have in particular included two extended chemical and isotope monitoring studies lasting for several years. These studies result in the identification of the fluid component sources. The CO2 stems from the lithospheric mantle - a deeper source area as in the case of CO2 sequestration. A distinct relationship was found between the steadily magmatic CO2-degassing and the recurrence of swarm earthquakes in the Novy Kostel focal zone close to the Cheb basin. Such areas with permanent CO2 fluxes from a well-known characterized deep source are especially suitable to study and test methods and method combinations for CO2 degassing monitoring. Several past and ongoing geophysical investigations concerning the geodynamical activity and the structural settings have been carried out to characterize the active fault systems. The lateral distribution of swarm seismicity is limited to a small number of focal zones, which have been periodically reactivated during the last years. The migration of fluids, uprising in permeable channels, is assumed to be the trigger of these earthquake swarms. Tectonic setting and sedimentary layers in the area have a great influence on the degassing situation of CO2 at the surface. Due to their permeability, faults act as preferential pathways for the upward migration and deep gases can escape to the atmosphere. Furthermore, regional patterns of diffuse CO2 emissions have been intensely studied to obtain insights into spatial and temporal variations of soil gas fluxes and concentrations.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.H23B1249S
- Keywords:
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- 1800 HYDROLOGY;
- 1848 HYDROLOGY / Monitoring networks;
- 8045 STRUCTURAL GEOLOGY / Role of fluids