Over the past decade, laboratory based X-ray computed micro-tomography (micro-CT) has given unique insights in the internal structure of complex porous materials in a broad range of applications, improving the understanding of pore scale processes and providing vital information for pore scale modelling. The non-destructive nature of micro-CT imaging, combined with dedicated X-ray transparent in situ equipment (eg. flow cells, tensile stages, heating and cooling stages) make it possible to monitor a changing pore structure over time in 3D. Recent advances in lab-based micro-CT hardware have pushed the temporal resolution from the hours down to seconds, enabling the visualization of fast dynamic processes and real-time imaging (Bultreys et al., 2016). Dynamic acquisitions however generate a vast amount of raw projection data, which needs to be reconstructed and further post processed. It is therefore key to quickly identify the interesting moments in time prior to reconstruction to optimize the amount of data that is generated, but also incorporated the added time dimension in the 3D analysis workflow to improve image quality.
In this work we present challenges and possibilities in dynamic micro-CT imaging for fast real-time acquisitions, reconstruction and analysis. The methodology and dedicated workflow from acquisition to analysis is illustrated using different flow experiments performed in a custom made X-ray transparent flow cell on limestone, sandstone and sintered glass samples. The first experiment, described in Boone et al. (2016), is single phase solute transport, where during continuous acquisition a tracer salt is injected in the pore space of a limestone sample. The capabilities of dynamic reconstruction of this experimental data is shown and analysis of the resulting 3D images enable distribution mapping of solute in the pore space through time. Other studies to be shown consist of two multiphase flow experiments of drainage and imbibition. In the drainage experiment, described in Bultreys et al. (2015), oil is injected in a brine saturated sandstone and the pore filling process can be visualized. By incorporating the temporal information in the 3D analysis of the pore space, individual pore filling events can be automatically identified and the size of these events monitored. For imbibition, on the other hand, water as wetting phase is injected in a sintered glass sample and the growth of water films and speed of pore filling can be analysed by reconstructing images from different time intervals and merging the appropriate temporal and local information for analysis.
Bultreys, T., et al. 2016. Fast laboratory-based micro-computed tomography for pore-scale research: Illustrative experiments and perspectives on the future. Advances in Water Resources 95:341-351.
Boone, M.A.,et al. 2016. In-situ, real time micro-CT imaging of pore scale processes, the next frontier for laboratory based micro-CT scanning. In 30th International symposium of the Society of Core Analysts. Society of Core Analysts (SCA), 2016.
Bultreys, T., et al. 2015. Real‐time visualization of Haines jumps in sandstone with laboratory‐based microcomputed tomography. Water Resources Research 51, 10: 8668-8676.
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