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Berlin Brandenburg

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  • 1
    In: Geophysical Research Letters, 28 September 2016, Vol.43(18), pp.9677-9685
    Description: We utilize synchrotron X‐ray tomographic imaging to investigate the pore‐scale characteristics and residual trapping of supercritical CO (scCO) over the course of multiple drainage‐imbibition (D‐I) cycles in Bentheimer sandstone cores. Capillary pressure measurements are paired with X‐ray image‐derived saturation and connectivity metrics which describe the extent of drainage and subsequent residual (end of imbibition) scCO trapping. For the first D‐I cycle, residual scCO trapping is suppressed due to high imbibition capillary number (Ca ≈ 10); however, residual scCO trapping dramatically increases for subsequent D‐I cycles carried out at the same Ca value. This behavior is not predicted by conventional multiphase trapping theory. The magnitude of scCO trapping increase is hysteretic and depends on the relative extent of the sequential drainage processes. The hysteretic pore‐scale behavior of the scCO‐brine‐sandstone system observed in this study suggests that cyclic multiphase flow could potentially be used to increase scCO trapping for sequestration applications. We observe cyclic pore‐scale behavior of supercritical CO2 (scCO2) via synchrotron X‐ray microtomography Residual scCO2 saturation increases over multiple drainage‐imbibition (D‐I) cycles reaching a value of 50% after three cycles The ultimate driver for this behavior may be a combination of cycling and associated surface chemistry reactions
    Keywords: Co 2 Sequestration ; Residual Trapping ; Capillary Trapping ; Cyclic Injections ; X‐Ray Microtomography ; Multiphase Flow
    ISSN: 0094-8276
    E-ISSN: 1944-8007
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  • 2
    Language: English
    In: Advances in Water Resources, December 2018, Vol.122, pp.251-262
    Description: We introduce a new method for defining a pore-body to pore-throat aspect ratio from segmented 3D image data, based on a connectivity metric applicable to porous media with widely varying pore-space connectivity and pore-space morphology. The ‘Morphological Aspect Ratio’ (MAR) is identified from the pore-space connectivity, using the Euler number (χ) as a function of a pore-space size defined by a morphological opening (erosion and dilation) of the pore space. We show that residual non-wetting phase trapping in porous media resulting from secondary imbibition scales with the MAR. Trapping was investigated in a Bentheimer sandstone core and five columns of partially sintered glass-particle packs with different combinations of glass beads and crushed glass ranging in size from 0.3 to 1.2 mm, resulting in porosity levels of 22–36%. Residual non-wetting phase trapping scales with the MAR, in contrast to the aspect ratio calculated with the traditional Maximum Inscribed Sphere (MIS) algorithm applied after partitioning the pore space into pore bodies and pore throats with a watershed transform followed by a region merging algorithm. This novel aspect ratio is a robust method that is less affected by segmentation errors compared to other methods for calculating aspect ratio and is applicable to residual non-wetting phase trapping resulting from capillary-driven flow of a wetting fluid through water-wet porous media.
    Keywords: Connectivity ; Capillary-Dominated Flow ; Morphological Opening ; Nonwetting Phase Trapping ; X-Ray Micro-Tomography ; Porous Media ; Engineering
    ISSN: 0309-1708
    E-ISSN: 1872-9657
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  • 3
    Language: English
    In: International Journal of Greenhouse Gas Control, March 2016, Vol.46, pp.175-186
    Description: We investigate capillary trapping and fluid migration via x-ray computed microtomography (x-ray CMT) of nonwetting phase (air) and wetting phase (brine) in Bentheimer sandstone cores which have been treated to exhibit different degrees of uniform wettability. x-Ray CMT scans were acquired at multiple steps during drainage and imbibition processes, as well as at the endpoints; allowing for assessment of the impact of wettability on nonwetting phase saturation and cluster size distribution, connectivity, topology and efficiency of trapping. Compared with untreated (water-wet) Bentheimer sandstone, cores treated with tetramethoxylsilane (TMS) were rendered weakly water-wet, and cores treated with octadecyltrichlorosilane (OTS) demonstrate intermediate-wet characteristics. As apparent contact angle increases, drainage flow patterns deviate from those derived for water-wet systems, total residual trapping and trapping efficiency decrease, and buoyancy plays a larger role during nonwetting phase mobilization; this has significant implications for CO migration and trapping during CO sequestration operations.
    Keywords: Wettability ; Drainage Flow Pattern ; Capillary Trapping ; Residual Trapping ; Pore Scale ; Geologic Co2 Sequestration ; Engineering
    ISSN: 1750-5836
    E-ISSN: 1878-0148
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  • 4
    Language: English
    In: Advances in Water Resources, Dec, 2013, Vol.62, p.47(12)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.advwatres.2013.09.015 Byline: Anna L. Herring, Elizabeth J. Harper, Linnea Andersson, Adrian Sheppard, Brian K. Bay, Dorthe Wildenschild Abstract: acents We examine the effect of NW phase connectivity on capillary trapping in porous media. acents We establish relationships of NW connectivity as a function of NW saturation. acents High initial NW connectivity results in reduced trapping for Bentheimer sandstone. acents Multiple drainage-imbibition cycles do not change the NW connectivity of the media. acents A WAG injection scheme reduces connectivity and promotes capillary trapping of CO.sub.2. Article History: Received 15 May 2013; Revised 25 September 2013; Accepted 27 September 2013
    ISSN: 0309-1708
    Source: Cengage Learning, Inc.
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  • 5
    Language: English
    In: International Journal of Greenhouse Gas Control, June 2014, Vol.25, pp.93-101
    Description: This work utilizes synchrotron-based x-ray computed microtomography (x-ray CMT) imaging to quantify the volume and topology of supercritical carbon dioxide (scCO ) on a pore-scale basis throughout the primary drainage process of a 6 mm diameter Bentheimer sandstone core. Experiments were performed with brine and scCO at 8.3 MPa (1200 psi) and 37.5 °C. Capillary pressure–saturation curves for the scCO -brine system are presented and compared to the ambient air-brine system, and are shown to overlay one another when pressure is normalized by interfacial tension. Results are analyzed from images with a voxel resolution of 4.65 μm; image-based evidence demonstrates that scCO invades the pore space in a capillary fingering regime at a mobility ratio = 0.03 and capillary number = 10 to an end-of-drainage brine saturation of 9%. We provide evidence of the applicability of previous two-dimensional micromodel studies and ambient condition experiments in predicting flow regimes occurring during scCO injection.
    Keywords: Supercritical Co2 ; Carbon Sequestration ; Capillary Fingering ; Drainage ; X-Ray Microtomography ; Engineering
    ISSN: 1750-5836
    E-ISSN: 1878-0148
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  • 6
    Language: English
    In: Advances in Water Resources, May 2015, Vol.79, pp.91-102
    Description: We investigate trapping of a nonwetting (NW) phase, air, within Bentheimer sandstone cores during drainage–imbibition flow experiments, as quantified on a three dimensional (3D) pore-scale basis via x-ray computed microtomography (X-ray CMT). The wetting (W) fluid in these experiments was deionized water doped with potassium iodide (1:6 by weight). We interpret these experiments based on the capillary–viscosity–gravity force dominance exhibited by the Bentheimer–air–brine system and compare to a wide range of previous drainage–imbibition experiments in different media and with different fluids. From this analysis, we conclude that viscous and capillary forces dominate in the Bentheimer–air–brine system as well as in the Bentheimer–supercritical CO –brine system. In addition, we further develop the relationship between initial (post-drainage) NW phase connectivity and residual (post-imbibition) trapped NW phase saturation, while also taking into account initial NW phase saturation and imbibition capillary number. We quantify NW phase connectivity via a topological measure as well as by a statistical percolation metric. These metrics are evaluated for their utility and appropriateness in quantifying NW phase connectivity within porous media. Here, we find that there is a linear relationship between initial NW phase connectivity (as quantified by the normalized Euler number, ) and capillary trapping efficiency; for a given imbibition capillary number, capillary trapping efficiency (residual NW phase saturation normalized by initial NW phase saturation) can decrease by up to 60% as initial NW phase connectivity increases from low connectivity ( ≈ 0) to very high connectivity ( ≈ 1). We propose that multiphase fluid-porous medium systems can be engineered to achieve a desired residual state (optimal NW phase saturation) by considering the dominant forces at play in the system along with the impacts of NW phase topology within the porous media, and we illustrate these concepts by considering supercritical CO sequestration scenarios.
    Keywords: Co2 Sequestration ; Topology ; Pore-Scale ; Force Balance ; Nonwetting Phase Trapping ; X-Ray Microtomography ; Engineering
    ISSN: 0309-1708
    E-ISSN: 1872-9657
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  • 7
    Language: English
    In: Advances in Water Resources, 2015, Vol.79, p.91(12)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.advwatres.2015.02.005 Byline: Anna L. Herring, Linnea Andersson, Steffen Schluter, Adrian Sheppard, Dorthe Wildenschild Abstract: * We investigate residual trapping of nonwetting (NW) phase (air) in sandstone cores. * We describe initial air configurations with connectivity metrics. * Factors influencing trapping are a function of dominant pore-scale forces. * Trapping efficiency decreases as initial air connectivity increases. * Pore-scale forces and NW connectivity are important for engineering applications. Article History: Received 23 August 2014; Revised 6 February 2015; Accepted 9 February 2015
    ISSN: 0309-1708
    Source: Cengage Learning, Inc.
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  • 8
    Language: English
    In: Advances in Water Resources, December 2013, Vol.62, pp.47-58
    Description: This work examines the influence of (i.e. post drainage) nonwetting (NW) fluid topology on total (i.e. after imbibition) NW phase saturation. Brine and air (used as a proxy for supercritical CO ) flow experiments were performed on Bentheimer sandstone; results were quantified via imaging with X-ray computed microtomography (X-ray CMT), which allows for three dimensional, non-destructive, pore-scale analysis of the amount, distribution, and connectivity of NW phase fluid within the sandstone cores. In order to investigate the phenomenon of fluid connectivity and how it changes throughout flow processes, the Bentheimer sandstone results are compared to previously collected X-ray CMT data from similar experiments performed in a sintered glass bead column, a loose packed glass bead column, and a column packed with crushed tuff. This allows us to interpret the results in a broader sense from the work, and draw conclusions of a more general nature because they are not based on a single pore geometry. Connectivity is quantified via the of the NW fluid phase; the Euler number of a particular sample is normalized by the maximum connectivity of the media, i.e. the Euler number of the system at 100% NW phase saturation. General connectivity-saturation relationships were identified for the various media. In terms of trapping, it was found that residual NW phase trapping is dependent on initial (i.e. post-drainage) NW phase connectivity as well as imbibition capillary number for the Bentheimer sandstone. Conversely, the sintered glass bead column exhibited no significant relationship between trapping and NW topology. These findings imply that for a CO sequestration scenario, capillary trapping is controlled by both the imbibition capillary number and the initial NW phase connectivity: as capillary number increases, and the normalized initial Euler number approaches a value of 1.0, capillary trapping is suppressed. This finding is significant to CO sequestration, because both the drainage (CO injection) and imbibition (subsequent water injection or infiltration) processes can be engineered in order to maximize residual trapping within the porous medium. Based on the findings presented here, we suggest that both the Euler number-saturation and the capillary number-saturation relationships for a given medium should be considered when designing a CO sequestration scenario.
    Keywords: Connectivity ; Topology ; Co2 Sequestration ; Capillary Trapping ; Porous Media ; X-Ray Tomography ; Engineering
    ISSN: 0309-1708
    E-ISSN: 1872-9657
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  • 9
    Language: English
    In: Advances in Water Resources, July 2018, Vol.117, pp.1-13
    Description: We explore how X-ray computed microtomography can be used to generate highly-resolved 3D biofilm datasets on length scales that span multiple pore bodies. The data is integrated into a study of the effects of flow rate on three-dimensional growth of biofilm in porous media. Three flow rates were investigated in model packed-bed columns. Biofilm growth was monitored during an 11-day growth period using a combination of differential pressure and effluent dissolved oxygen measurements. At the end of the growth period, all columns were scanned using X-ray computed microtomography and a barium sulfate-based contrast agent. The resulting images were prepared for quantitative analysis using a novel image processing workflow that was tailored to this specific system. The reduction in permeability due to biofilm growth was studied using both transducer-based pressure drop measurements and image-based calculations using the Kozeny–Carman model. In addition, a set of structural measures related to the spatial distribution of biofilms were computed and analyzed for the different flow rates. We generally observed 1 to 2 orders of magnitude decrease in permeability as a result of bioclogging for all columns (i.e, across flow rates). The greatest average permeability and porosity reduction was observed for the intermediate flow rate (4.5 ml/h). A combination of results from different measurements all suggest that biofilm growth was oxygen limited at the lowest flow rate, and affected by shear stresses at the highest flow rate. We hypothesize that the interplay between these two factors drives the spatial distribution and quantity of biofilm growth in the class of porous media studied here. Our approach opens the way to more systematic studies of the structure-function relationships involved in biofilm growth in porous media and the impact that such growth may have on physical properties such as hydraulic conductivity.
    Keywords: Biofilms ; Granular Porous Media ; X-Ray Computed Microtomography ; Image Processing ; Statistical Learning ; Fluid Phase Topology ; Engineering
    ISSN: 0309-1708
    E-ISSN: 1872-9657
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