Techn. Universiẗat, Diss., 2005--Chemnitz.

Universiẗat, Landw. Fak., Diss.--Halle, 2005.

We theoretically and experimentally investigate the impact of pore space structure, wettability, and surface roughness on the displacement front, trapping, and sweeping efficiency at low capillary numbers. The microstructure of (i) 2D geologically-realistic media (2D natural sand and sandstone), (ii) a topological 3D-2D-transformation (2D sand analog), and (iii) geometrically representative media (Delaunay Triangulation) were studied over a wide range of wettability from water-wet to oil-wet systems provided by using various fluid-pairs. We observed the transition (compact to fractal) in the displacement front caused by local instabilities identified by Cieplak and Robbins. The trapping efficiency of 2D natural microstructures showed a non-monotonous dependency on wettability, whereas a crossover from no trapping to maximal trapping was observed in 2D patterns of circular grains. For the first time, we compared identical experimental microstructures with simulation, capturing the key elements of the invasion process. We demonstrated that corner flows occur particularly in low-porosity media, where the smaller grain-grain distance hindered the corner-flow bridging. These insights could improve the CO2 geological storage and Enhanced Oil Recovery processes.

The field of geosciences, including geophysics, plays a crucial role in addressing society's pressing concerns related to energy demand, climate change, resource preservation, and environmental protection. Reactive systems encountered in this context are characterized by intricate interactions among various phases, environmental conditions, physical and chemical processes. Achieving a comprehensive understanding of these processes and quantitatively evaluating reactive systems necessitates a holistic scientific approach. This approach encompasses efficient categorization of reactive systems, the development of appropriate experimental and computational tools, and the collection and dissemination of relevant data. In this context, this thesis contributes to geophysics and petrophysics with a focus on reactive systems. It presents and interprets laboratory datasets that address various complex aspects of rock behavior, including the presence of graphite, resulting anisotropy, and the challenging petrophysical characteristics of carbonate rocks. This compilation of research results provides a multifaceted perspective on the complex nature of rocks, including their mineralogical, physical, and chemical properties. It thus contributes to a deeper comprehension of electrical rock properties and their practical utility. Upon examining carbonate rocks and the response of graphitic schist to CO$_\mathrm{2}$ under reservoir conditions, it becomes clear that the impact of increased reactivity in a system on geophysical parameters varies depending on the specific characteristics of the rocks and systems under investigation. Consequently, geophysical methods aiming at a quantitative assessment of reactive systems must exhibit robustness and efficiency in order to be effectively applied in a site- and system-specific manner. Expanding on this foundation, computational methods have been developed to aid in the quantitative analysis of reactive processes in laboratory experiments. These methods also serve as tools for gaining insights into the origin of rock properties and the impact of microstructure variation. Furthermore, inversion techniques are introduced in conjunction with custom-designed experiments within the field of petrophysics. The resultant software tool is made publicly accessible. The research further delves into the exploration of how physical properties of rocks are influenced by their microstructure, as well as how the stochastic nature of pore space geometry can introduce variability and uncertainty in rock physics data. This investigation was carried out through microstructure modeling and finite element simulations. Leveraging these tailored computational techniques allowed for a comprehensive understanding of laboratory data, facilitating robust generalizations and contextualization for field applications and site-specific integrated interpretation. To illustrate the application in a complex natural reactive system, a field study focusing on coastal fumarolic vents in volcanic terrain was carried out and is presented. The challenges, prospects and visualization strategies for integrating simulation or inversion results from different methods are examined. Effective evaluation of complex sites requires open access to existing knowledge, including laboratory datasets. Consequently, this work documents and provides openly accessible examples of complex multi-method laboratory datasets to facilitate better understanding, re-evaluation and application in the field. Finally, the handling of multi-reactive systems in field applications is discussed. It involves the integration of three-dimensional subsurface models with petrophysical insights related to multi-reactive systems. These models are calibrated using additional complementary data from surface or borehole sources. This integrated approach enables a quantitative assessment of site-specific multi-reactive systems.

Capillary trapping plays a central role in the geological storage of CO2, oil recovery, and water soil infiltration. The key aim of this study is to investigate the impact of surface properties (wettability, roughness, heterogeneous mineral composition) on the dynamics of quasi-static fluid displacement process and capillary trapping efficiency in porous medium. We concluded that for homogeneous wet smooth glass beads surfaces, a transition in fluid displacement pattern occurs from a compact (for θ < 90°; imbibition process) to a fractal front-pattern (for θ > 90°; drainage process) leading to a crossover in capillary trapping efficiency from zero to maximum. The impact of surface roughness on capillary trapping efficiency was also studied, and an opposite trends in terms of wettability dependency was observed. Rough natural sands surfaces depicts a non-monotonous wettability dependency, i.e. a transition from maximal trapping (for θ < 90°) to no-trapping occurs (at θ = 90°), followed by an increase to medium trapping (for θ > 90°). For a fractional-wet media, the percolating cluster of hydrophobic sediments (connected hydrophobic pathways) characterize the fluid displacement pattern and trapping efficiency.