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Institut für Wasser- und Umweltsystemmodellierung - IWS



"CO2 Storage into Dipped Saline Aquifers Including Ambient Water Flow "

In this thesis, the storage of carbon dioxide into saline aquifers or aquifer parts with a dip angle and ambient water flow in down dip direction shall be examined and discussed with the help of numerical models. It will be determined, how different parameters like dip angle, injection pressure or injection depth influence the propagation behavior of the injected CO2. Different occurring processes will be examined and explained. The dimensionless Van-Lookeren number, which describes the ratio of buoyancy forces to viscous forces, will be used to characterize the propagation behavior. Moreover, rough estimations for the expected direction of the propagation will be presented. Finally, recommendations for the use of such aquifers and for the suitability for carbon dioxide storage will be made.

The first part of the thesis gives a brief introduction to CO2-sequestration, the underlying reasons and the dominating physical properties and processes. These are further explored with the help of numerical models. The numerical and mathematical model concepts that are used for the simulations are explained. Then, a reference model is set up and presented. The process of injecting CO2 into a dipped aquifer, where formation water is flowing down dip, is very complex and includes a bunch of parameters that have an influence on the flow and propagation behavior. Several two-dimensional models are used then to simulate CO2 sequestration in such aquifers with different parameters as the reference model like aquifer depth, dip angle or water flow. With the help of these simulations the influence of these parameters on the propagation behavior of the injected CO2 is examined. Two dimensionless numbers are applied to describe the influence of these parameters on the shape of the evolving plume.

In the second part, real world data is used to build up a three-dimensional numerical model of a dipped saline aquifer at a prospective site. Due to high recharge rates >from upstream there is a formation water flow down dip the aquifer. The behavior of CO2, which is injected into this flow is examined and explained with the help of the observations that were made in the two-dimensional models. Statements about the suitability of the given aquifer and different possibilities for long-term storage are made. Various parameter setups are tested and and evaluated.