Benjamin Blykers

Bio: Benjamin Blykers is an academic researcher from Ghent University. The author has contributed to research in topics: Medicine & Permeability (earth sciences). The author has an hindex of 2, co-authored 3 publications receiving 22 citations.

In Situ Triaxial Testing To Determine Fracture Permeability and Aperture Distribution for CO2 Sequestration in Svalbard, Norway

Abstract: On Svalbard, Arctic Norway, an unconventional siliciclastic reservoir, relying on (micro)fractures for enhanced fluid flow in a low-permeable system, is investigated as a potential CO2 sequestration site. The fractures' properties at depth are, however, poorly understood. High resolution X-ray computed tomography (micro-CT) imaging allows one to visualize such geomaterials at reservoir conditions. We investigated reservoir samples from the De Geerdalen Formation on Svalbard to understand the influence of fracture closure on the reservoir fluid flow behavior. Small rock plugs were brought to reservoir conditions, while permeability was measured through them during micro-CT imaging. Local fracture apertures were quantified down to a few micrometers wide. The permeability measurements were complemented with fracture permeability simulations based on the obtained micro-CT images. The relationship between fracture permeability and the imposed confining pressure was determined and linked to the fracture apertures. The investigated fractures closed due to the increased confining pressure, with apertures reducing to approximately 40% of their original size as the confining pressure increased from 1 to 10 MPa. This coincides with a permeability drop of more than 90%. Despite their closure, fluid flow is still controlled by the fractures at pressure conditions similar to those at the proposed storage depth of 800-1000 m.

Tunable X-ray dark-field imaging for sub-resolution feature size quantification in porous media.

Abstract: X-ray computed micro-tomography typically involves a trade-off between sample size and resolution, complicating the study at a micrometer scale of representative volumes of materials with broad feature size distributions (e.g. natural stones). X-ray dark-field tomography exploits scattering to probe sub-resolution features, promising to overcome this trade-off. In this work, we present a quantification method for sub-resolution feature sizes using dark-field tomograms obtained by tuning the autocorrelation length of a Talbot grating interferometer. Alumina particles with different nominal pore sizes (50 nm and 150 nm) were mixed and imaged at the TOMCAT beamline of the SLS synchrotron (PSI) at eighteen correlation lengths, covering the pore size range. The different particles cannot be distinguished by traditional absorption µCT due to their very similar density and the pores being unresolved at typical image resolutions. Nevertheless, by exploiting the scattering behavior of the samples, the proposed analysis method allowed to quantify the nominal pore sizes of individual particles. The robustness of this quantification was proven by reproducing the experiment with solid samples of alumina, and alumina particles that were kept separated. Our findings demonstrate the possibility to calibrate dark-field image analysis to quantify sub-resolution feature sizes, allowing multi-scale analyses of heterogeneous materials without subsampling.

Detecting thin adhesive coatings in wood fiber materials with laboratory-based dual-energy computed tomography (DECT)

Abstract: Abstract The distribution and good spreading of adhesive resins is critical for the wood-based panels industry. Full 3D non-destructive characterization is necessary, but methods are limited due to the chemical similarities between the resins and the wood fibers. For X-ray microtomography ( $$\mu $$ μ CT), the doping of the resin with a highly attenuating contrast agent is necessary to visualize the resin distribution. However, the attenuation signal remains hard to segment clearly due to partial volume effects in the image, and phase mixing in the material. To help in the identification of the doped resin, dual-energy X-ray CT (DECT) is used to exploit the contrast agent’s K-edge, based on simulations which take into account the polychromatic properties of the X-ray tube and detector response. The contrast agent’s identification with DECT is validated with elemental mapping using scanning electron microscopy combined with energy-dispersive spectroscopy (SEM-EDX) on the surface of a wood-based panel sample, using data fusion between DECT and SEM-EDX. Overall, DECT results here in the first 3D identification of doped resin inside wood fiberboards, guiding the industry’s efforts in further improving the durability of wood-based panels.

Exploration of the X-ray Dark-Field Signal in Mineral Building Materials

Abstract: Mineral building materials suffer from weathering processes such as salt efflorescence, freeze–thaw cycling, and microbial colonization. All of these processes are linked to water (liquid and vapor) in the pore space. The degree of damage following these processes is heavily influenced by pore space properties such as porosity, pore size distribution, and pore connectivity. X-ray computed micro-tomography (µCT) has proven to be a valuable tool to non-destructively investigate the pore space of stone samples in 3D. However, a trade-off between the resolution and field-of-view often impedes reliable conclusions on the material’s properties. X-ray dark-field imaging (DFI) is based on the scattering of X-rays by sub-voxel-sized features, and as such, provides information on the sample complementary to that obtained using conventional µCT. In this manuscript, we apply X-ray dark-field tomography for the first time on four mineral building materials (quartzite, fired clay brick, fired clay roof tile, and carbonated mineral building material), and investigate which information the dark-field signal entails on the sub-resolution space of the sample. Dark-field tomography at multiple length scale sensitivities was performed at the TOMCAT beamline of the Swiss Light Source (Villigen, Switzerland) using a Talbot grating interferometer. The complementary information of the dark-field modality is most clear in the fired clay brick and roof tile; quartz grains that are almost indistinguishable in the conventional µCT scan are clearly visible in the dark-field owing to their low dark-field signal (homogenous sub-voxel structure), whereas the microporous bulk mass has a high dark-field signal. Large (resolved) pores on the other hand, which are clearly visible in the absorption dataset, are almost invisible in the dark-field modality because they are overprinted with dark-field signal originating from the bulk mass. The experiments also showed how the dark-field signal from a feature depends on the length scale sensitivity, which is set by moving the sample with respect to the grating interferometer.

General solution for quantitative dark-field contrast imaging with grating interferometers

Abstract: Dark-field contrast imaging with grating interferometers has proven to hold huge potential for numerous applications with X-rays and with neutrons conveying biology and medicine as well as engineering and magnetism, respectively. However, a concept to extract quantitative information is still missing. Here a general theory as well as a measurement strategy is introduced, allowing extraction of quantitative small-angle scattering information such as structure sizes and scattering cross sections. The validity of the description is demonstrated by a specific example from literature.

Influence of loading and unloading velocity of confining pressure on strength and permeability characteristics of crystalline sandstone

Abstract: The triaxial compression test of crystalline sandstone under different loading and unloading velocity of confining pressure is carried out by using the self-made “THM coupled with servo-controlled seepage apparatus for containing-gas coal”, analyzed the strength, deformation and permeability characteristics of the sample, the results show that: with the increase of confining pressures loading-unloading velocity, Mohr’s stress circle center of the specimen shift to the right, and the ultimate intensity, peak strain and residual stress of the specimens increase gradually. With the decrease of unloading velocity of confining pressure, the axial strain, the radial strain and the volumetric strain of the sample decrease first and then increases, but the radial strain decreases more greatly. The loading and unloading of confining pressure has greater influence on axial strain of specimens. The deformation modulus decreases rapidly with the increase of axial strain and the Poisson’s ratio decreases gradually at the initial stage of loading. When the confining pressure is loaded, the deformation modulus decrease gradually, and the Poisson's ratio increases gradually. When the confining pressure is unloaded, the deformation modulus increase gradually, and the Poisson’s ratio decreases gradually. When the specimen reaches the ultimate intensity, the deformation modulus decreases rapidly, while the Poisson’s ratio increases rapidly. The fitting curve of the confining pressure and the deformation modulus and the Poisson’s ratio in accordance with the distribution of quadratic polynomial function in the loading-unloading confining pressure. There is a corresponding relationship between the evolution of rock permeability and damage deformation during the process of loading and unloading. In the late stage of yielding, the permeability increases slowly, and the permeability increases sharply after the rock sample is destroyed. Fitting the permeability and confining pressure conform to the variation law of the exponential function.

Innovations in laboratory-based dynamic micro-CT to accelerate in situ research.

Abstract: In the past few years, dynamic computed tomography (CT) approaches or uninterrupted acquisitions of deforming materials have rapidly emerged as an essential technique to understand material evolution, facilitating in situ investigations ranging from mechanical deformation to fluid flow in porous materials and beyond. Developments at synchrotron facilities have led this effort, pointing to the future of the technique. In the laboratory, recent developments at TESCAN XRE have made it possible to image, reconstruct and inspect dynamic processes in the laboratory with a temporal resolution below 10 s, meaning that an entire acquisition from 0 to 360° is completed within 10 s. The aim of this study is to explore the challenges and innovations that have led to the ability to perform high speed, dynamic acquisitions. A unique horizontally rotating gantry based micro-CT system was developed to facilitate complex in situ experiments. In doing so, the sample stays fixed while source and detector are uninterruptedly rotating around a vertical axis. In this work, the dynamic CT method with this rotating gantry based system will be described by two application examples: (1) deformation and collapse of a delicate beer foam and (2) in situ baking process of pastry. For the pastry baking process, an oven was needed to reach baking temperature. In a conventional micro-CT system, where the sample rotates, it is not so obvious to rotate an oven with sensor and heating cables. On the other hand, the delicate foam of a collapsing beer head is able to rotate, but because of the tangential convection during fast rotation (<10 s), it could influence the bubble detachment and liquid drainage and thus also the foam degradation. To investigate both processes, a horizontally rotating gantry based micro-CT is required. For both examples it was possible to quantify the key parameters such as pore size and distribution to better understand the rise and fall of porous foams. These examples will highlight the recent progress in adapting micro-CT workflows to accommodate uninterrupted imaging of dynamic events and point to opportunities for future continued development. LAY DESCRIPTION: Micro-CT allows the nondestructive visualisation of internal structures and is being used routinely in the field of Material Science, Geoscience, Life Science and more. Because of its nondestructive aspect, micro-CT is optimal to take repetitive scans of the same sample over time. The combination of taking different scans over time is so called time-resolved CT. By doing so, crucial insights can be obtained on how materials form, deform and perform over time or under certain external conditions. TESCAN XRE have made it possible to image, reconstruct and inspect dynamic processes in the laboratory with a temporal resolution below 10 s. The dynamic CT method will be described through the lens of two application examples: (1) deformation and collapse of a delicate beer foam and (2) in situ baking process of pastry. These examples will highlight the recent progress in adapting micro-CT workflows to accommodate imaging of dynamic events and point to opportunities for future continued development.