Joanna Dziadkowiec:
Title: Mineral dissolution-replacement reactions under confinement.
Abstract: Interface-coupled, fluid-induced mineral transformation reactions are widespread in porous rocks and materials. These dissolution-replacement reactions frequently occur under the spatial confinement of pores. However, it is experimentally challenging to access the in-situ nanoscale information about these dynamic processes. In this talk, I will present recent surface forces apparatus (SFA) experiments that address these challenges. SFA is a white light interferometry-based force measuring technique that can provide information about the changing distance between dissolving and growing confined surfaces in real time. Based on the SFA results, I will show how the outcome of mineral dissolution-replacement reactions under confinement depends on the relative solubilities of the dissolving mineral and the new precipitating phases. I will also discuss how these findings can be related to weathering processes observed at the macroscale.
Paiman Shafabakhsh:
Title: Neutron imaging of fluid mixing in rocks with carbonate precipitation
Abstract: Flow and mixing processes in porous media control many natural and industrial systems, such as microbial clogging, oil extraction, and effluent disposal. Mineral precipitation in porous media takes place locally and controls permeability evolution. Fluid mixing properties under the influence of evolving porosity can be explored through flow visualization in laboratory experiments. Neutron imaging has proven very useful for in-situ studies of fluid flow imaging in porous rocks. In this talk, I will present the results of the performed experiment of fluid mixing in Bentheim sandstone before and after in-situ carbonate precipitation. The precipitation of calcium carbonate (calcite) crystals was induced by reactive mixing between two aqueous solutions containing of CaCl2 and Na2CO3. Using the neutron beamline at the Paul Scherrer Institute, we explored the mixing of two miscible fluids, a solution of heavy water (D2O) and a solution with cadmium (CdCl2), an element that provides good contrast with neutron imaging. The findings of this experimental study are useful in progressing the knowledge in the domain of reactive solute and contaminant transport in the subsurface.
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