WP 1.2
The near-surface underground in Northern Germany consists of unconsolidated sediments. These are for instance made up of more or less horizontal deposits of Miocene Lignite Sand as aquifers and Mica Clays as aquitards as well as highly heterogeneous occurrences of Pleistocene sand and till. These near-surface structures were mainly influenced by cycles of glaciation in the last 500,000 years, but also by rising salt diapirs and salt walls. The Miocene Lignite Sand and the Pleistocene aquifers are protected resources as they constitute major sources for potable water in the region.
Using the near-surface underground in the context of changing the energy supply systems („Energiewende“) can influence these protected resources, for instance by heat storage actions in these or adjacent formations or by potential leakages of gases like H2 or CH4, which can be stored in the deep subsurface. However, it cannot be deducted that these induced effects automatically affect the groundwater quality in a negative way. In order to evaluate impacts, which are planned in case of heat storage and undesired in case of gas leakages, laboratory experiments and numerical simulations are conducted in the ANGUS+ project. The presented work package serves the parameterization of near-surface protected resources preparing these further investigations. The parameterization includes the regarded geological structures and their properties. As geological structures, model sites from the Northern German region were selected. The properties comprise for instance aquifer and aquitard permeabilities, the groundwater`s chemical composition, and mineralogical as well as mechanical parameters of the sediments. In addition, potential and realistic leakage pathways and leakage rates are to be defined.
Since these required parameters are not available to equal extents, we start by describing the data inventory and by performing a deficit analysis. Major structures of the near-surface formations are known, but small-scale heterogeneities, which are present especially in glacial sediments, are not determined in detail. Data of the groundwater compositions are available, since they are surveyed by public monitoring networks and by private water suppliers. Mineralogical data of the near-surface sediments were only occasionally analyzed in the past, so that the presented work package also includes analyzing this parameter using drill cores. These analyses are complemented by the geochemical sediment characterization, where the focus lies on trace metal concentrations, sorption, and cation exchange capacities.
For describing leakages (including leakage pathways, leakage rates, and induced reactions) and monitoring their effects, conceptual models are being developed. These regard the geological situation (sequence, position, and characteristics of the formations) in Northern Germany. The parameterization also comprises petro-physical parameters and relations like porosities, permeabilities, water compositions, densities, electric water and rock conductivities, and compression and sheer modules for various near-surface formations from literature data, as they are needed for a geophysical monitoring.
Such data are especially needed for defining realistic scenarios in the work packages WP 3.3 and WP 3.4, but also for designing laboratory experiments such as in WP 1.7 and WP 1.8. In addition, links exist to the WP 1.1 and WP 1.3, which also focus on the acquisition and evaluation of subsurface parameters.
