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Geological Field Model (WP2.1)
Knowledge of the subsurface geology is a precondition for all issues associated with the storage of CO2. Consequently, the work package WP 2.1 has a central position within the CO2SINK project and exhibits strong relations to other work packages. The main objective of WP 2.1 is to characterize the subsurface geological conditions at Ketzin. Particular emphasis is given on the geological structure, the reservoir and caprock characteristics, and the geology/hydrogeology of the shallow subsurface. The two latter issues play an important role in the assessment of risk linked with the storage of CO2.
At Ketzin, geological data are available from previous exploration. These data need to be scrutinized and implemented in a database available online to all project partners. The database includes structural, lithological, petrophysical, hydrogeological, and thermal data. Most of the data originated from seismic surveys and from boreholes drilled in the past during several exploration campaigns. These data form the basis for a numerical geological model to be generated at different scale using different software tools.
The drilling of the CO2SINK boreholes will provide valuable geological data in addition to what is known in the area. From the analysis of drill-core and cuttings and of geophysical borehole logs new data on stratigraphy, lithology, and petrophysical properties (WP 2.1, WP 5.1) are expected. Laboratory measurements on core from the reservoir and caprock (WP 2.1, WP 3.1) allow an insight into the mineralogical composition of these rocks and into possible fluid (CO2)-rock interactions. The results from surface and borehole seismics (WP 2.3) prior and after the injection of CO2 provide information on the existence of fault systems (which in the worst case could serve as CO2 pathways to the surface) and on the internal structure of the storage formation. A hydrogeological model of the near-surface Quaternary aquifer system at Ketzin (WP 2.1) will complement the near-surface geochemical monitoring (WP 2.2) contributing to risk assessment (WP 4.1). The geological data and models form the basis for predictive models of the CO2 migration in the CO2SINK reservoir formation, the Stuttgart Formation (WP 6.1).
Work plan
Pre-drilling phase
- Compilation and assessment of geological data from former exploration (e.g. of over 200 boreholes and many seismic sections) and implementation of data into the CO2SINK data information system (CO2SIS)
- Set-up of a computerized geological field model (Landmark system)
- Analysis of lithological features of caprock and reservoir rock including petrography and mineralogy using existing old cores
- Interpretation of the CO2SINK 3-D seismic baseline data and implementation of the results into the numerical geological field model
- Development of a pre-drilling litho-log for the CO2SINK drilling
Drilling phase
- Support of sample handling/sample preparation
- Support by geological expertise of drilling operations, mud-logging, and perforation
- Development of a borehole stratigraphy/lithology log
Post-drilling phase
- Analysis of CO2SINK cores for lithological features and selected petrophysical properties including basic petrographic, mineralogical, and thermal parameters
- Characterization of reservoir rock and caprock for risk assessment
- Update of the geological model on the basis of results from geophysical monitoring prior and after CO2 injection.
Work in WP 2.1 is conducted by the GeoForschungsZentrum (GFZ) Potsdam, Section 5.2 (http://www.gfz-potsdam.de/pb5/pb52/ewelcome.html) and the Geological Survey of Denmark and Greenland (GEUS) in Copenhagen (www.geus.dk).
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