A new approach to understanding fluid behavior in porous materials
Gijs Wensink defended his PhD thesis at the Department of Mechanical Engineering on January 16.
Storing gases such as CO₂ and hydrogen underground is expected to play an important role in tackling climate change and supporting the energy transition. To ensure this storage is safe, efficient, and long-lasting, it’s crucial to understand in detail how fluids such as water and gas move through the tiny pores inside rocks and other porous materials. At extremely small scales, water can form films along rock surfaces that strongly influence how easily gas can be injected, stored, and recovered. In his PhD research, Gijs Wensink developed and applied a new experimental approach that makes it possible to observe and measure these water films with unprecedented precision. By combining advanced atomic force microscopy with three-dimensional X-ray imaging, he was able to directly link nanoscale water film behavior to fluid movement at the scale of individual pores.
The results from this research show that water films behave in complex and sometimes unexpected ways. In some rocks, film formation is delayed because water must first slowly pass through very small internal pores. During drying of rocks, such as during injection of dry hydrogen, the films can change rapidly in thickness due to sudden pore-scale fluid rearrangements. When salty water is present, minerals can crystallize within the water films during evaporation, causing the films to persist longer and potentially altering the rock surface itself. These processes can influence fluid movement underground and affect long-term storage behavior.
Fibrous porous materials
Gijs Wensink also studied fibrous porous materials, which are relevant in technical applications such as filters, absorbents, and engineered sponges. Similarly to the rocks that were studied, the fibers contain microporosity, which impacts flow behavior. In fibrous media, a combination of gravity and capillarity was found to play a role in fluid displacement.
Impact on large scales
Overall, this research demonstrates that processes occurring at extremely small scales can have a major impact on large-scale multiphase and reactive transport processes. By improving the ability to observe and understand these mechanisms, this research supports the development of safer underground gas storage and improved material design to advance the energy transition.
This research is part of the NWO DeepNL project.
Title of PhD thesis: Supervisors: Dr. Maja Rücker and Prof. David Smeulders.