Roman Koch

Lithofazielle Reservoircharakterisierung zur geothermischen Nutzung des Malm im Großraum München

ZusammenfassungDie zunehmende geothermische Nutzung des Malm im Untergrund des Großraums München erforderte ein besseres Systemverständnis des Tiefengrundwasserleiters. Auf Basis einer lithofaziellen Bewertung von 17 Malm-Geothermiebohrungen als ein Baustein einer integrierten Reservoircharakterisierung, konnte nun ein direkter Zusammenhang zwischen Lithofazies und Hydraulik abgeleitet werden. Demnach stellen im Malm des tiefen Untergrunds vorwiegend dolomitisierte Massenkalke den Grundwasserspeicher dar. Die Bohranalysen führen zu einer vereinfachten hydrostratigraphischen Gliederung, wonach der liegende Malm alpha bis gamma als Grundwassergeringleiter fungiert, Malm delta und epsilon einen großräumig, flächig verbreiteten, relativ homogenen Grundwasserleiter darstellt und der Malm zeta aufgrund der lateral stark variierenden Fazies sowohl als Grundwasserleiter, als auch Geringleiter ausgeprägt sein kann. Primärfaziell unterschiedliche Ablagerungsräume der Malmkarbonate in Schwellen- oder Beckenposition bedingen, zusammen mit der später erfolgten Dolomitisierung, ob eine Geothermiebohrung in einem hydraulisch „guten“ oder „ungünstigen“ Gebiet niedergebracht wurde. Aus den Daten ergibt sich eine neue Explorationsstrategie, die neben dem bisherigen strukturgeologischen Fokus nun vor allem auf die fazielle Ausprägung des Malm gerichtet ist.AbstractThe significant increase of geothermal energy production from the Malm reservoir in the greater area of Munich requires better understanding of the associated aquifer system. In this article, a good correlation between lithofacies and hydraulics is found on the basis of lithofacies evaluation of 17 geothermal wells. The main reservoir capacity within the Malm is made up by predominantly dolomitized massive limestones. Well analyses led to a simplified hydrostratigraphic profile, in which the lower Malm units (alpha to gamma) act as aquitards while Malm delta and epsilon units show a two-dimensional widespread and relatively homogeneous aquifer. Malm zeta can develop both aquifer- and aquitard-characteristics due to significant lateral facies changes. Facies changes depend largely on the basin position and subsequent dolomitisation is a crucial factor for the yield of wells drilled in this area. Based on these results, a new exploration strategy should focus more on facies characteristics than on structural features within the Malm Reservoir.

Petrographical and petrophysical properties of sandstones: statistical analysis as an approach to predict material behaviour and construction suitability

Most studies dealing with material properties of sandstones are based on a small data set. The present study utilizes petrographical and petrophysical data from 22 selected sandstones and ~300 sandstones from the literature to estimate/predict the material and weathering behaviour of characteristic sandstones. Composition and fabric properties were determined from detailed thin section analyses. Statistical methods applied consist of data distributions with whisker plots and linear regression with confidence regions for the petrophysical and weathering properties. To identify similarities between individual sandstones and to define groups of specific sandstone types, principal component and cluster analyses were applied. The results confirm an interaction between the composition, depositional environment, stratigraphic association and diagenesis, which leads to a particular material behaviour of sandstones. Three different types of pore radii distributions are observed, whereby each is derived from different pore space modifications during diagenesis and is associated with specific sandstone types: (1) bimodal with a maximum in capillary and micropores, (2) unimodal unequal with a maximum in smaller capillary pores and (3) unimodal equable with a maximum in larger capillary pores. Each distribution shows specific dependencies to water absorption, salt loading and hygric dilatation. The strength–porosity relationship shows dependence on the content of unstable lithic fragments, grain contact and type of pore radii distribution, cementation and degree of alteration. Sandstones showing a maximum of capillary pores and micropores (bimodal) exhibit a distinct hygric dilatation and low salt resistance. These sandstones are highly immature sublitharenites–litharenites, characterized by altered unstable rock fragments, which show pointed-elongated grain contacts, and some pseudomatrix. Quartz arenites and sublitharenites–litharenites which are strongly compacted and cemented, show unimodal unequal pore radii distributions, low porosity, high strength and a high salt resistance. The presence of swellable clay minerals in sublitharenites–litharenites leads to a medium to high hygric dilatation, whereas quartz arenites show little hygric dilatation. Sandstones with unimodal equal pore radii distribution mostly belong to weakly compacted and cemented mature quartz arenites. These are characterized by high water absorption and high porosity, low to medium strength and a low salt resistance. The data compiled in this study are used to create a sandstone quality catalogue. Since material properties are dependent on many different parameters of influence, the transition between different lithotypes is fluent.

Path Heuristics Using ACO for Inter-domain Routing in Mobile Ad Hoc and Sensor Networks

We investigate the use of biologically inspired routing heuristics in the field of inter-domain routing in sensor networks. Instead of relying on classical topology control techniques for routing in sensor networks, the use of geographical coordinates has been investigated for self-organized and fully distributed message forwarding. However, the identification of the nodes’ positions is either expensive in terms of necessary equipment or message exchange. Therefore, the use of virtual coordinates has been investigated in this domain. The key advantage is that these virtual identifiers can also be used for data management similar as in a DHT. It is, however, extremely challenging to provide routing functionality between multiple independent networks or network domains. In previous work, we developed the VCP that provides all the means for creating and maintaining such virtual identifiers and that is even able to route between neighboring network domains. This paper extends VCP by providing a generalized inter-domain routing framework using ACO for optimizing routes between multiple network domains. In extensive simulations, we evaluated this routing bio-inspired heuristic. The obtained results clearly demonstrate that ACO is very efficient even in highly mobile scenarios.