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Binary segmentation of volumetric images of porous media is a crucial step towards gaining a deeper understanding of the factors governing biogeochemical processes at minute scales. Contemporary work primarily revolves around primitive techniques based on global or local adaptive thresholding that have known common drawbacks in image segmentation. Moreover, the absence of a unified benchmark prohibits quantitative evaluation, which further undermines the impact of existing methodologies. In this study, we tackle the issue on both fronts. First, by drawing parallels with natural image segmentation, we propose a novel, and automatic segmentation technique, 3D Quantum Cuts (QCuts-3D) grounded on a state-of-the-art spectral clustering technique. Secondly, we curate and present a publicly available dataset of 68 multiphase volumetric images of porous media with diverse solid geometries, along with voxel-wise ground truth annotations for each constituting phase. We provide comparative evaluations between QCuts-3D and the current state-of-the-art over this dataset across a variety of evaluation metrics. The proposed systematic approach achieves a 26% increase in AUROC (Area Under Receiver Operating Characteristics) while achieving a substantial reduction of the computational complexity over state-of-the-art competitors. Moreover, statistical analysis reveals that the proposed method exhibits significant robustness against the compositional variations of porous media. publishedVersion

Gas production from hydrate-bearing sediments requires methane dissociation, which induces two-phase gas flow, mobilizing fine clay particles from within saturated pores. Fines migration within sandy sediments results in subsequent pore clogging, reducing reservoir connectivity. Sediments complex pore morphology, require direct 3D microscopic pore-scale imaging to investigate fines' influence on the porous media. The work uses synchrotron microcomputed tomography, to understand how fines migration due to gas injection, affects pore morphology and gas connectivity within sandy sediments. The goal is to study the impact of fines type and content at different gas injection stages, on gas flow regime and sediments rearrangement. Six saturated samples of sand and fines mixtures (Kaolinite and Montmorillonite at different contents) underwent four stages of gas injection during in-situ 3D scanning. X-ray images were segmented for direct visualization, as well to quantify gas ganglia distribution, also to extract pore networks to statistically measure changes in pore and throats distributions, and to simulate single-phase and relative permeability. Findings reveal that the extent of deformation to pore morphology increases with fines content and gas injection regardless of fines type. High kaolinite content (equal to or larger than 6%) results in fractured porous media, while high montmorillonite content (equal to or larger than 5%) results in disconnected vuggy media. Lower contents cause a gradual reduction in pore and throat sizes during gas injection. As fines content increases, clogging intensifies, thus gas connectivity and flow regime changes from connected capillary to disconnected vugs and microfractures. Both hydrophobic and hydrophilic fines reduced throat sizes, due to dislocations in sand grains. A unique pattern is discovered using pore networks, which describe pore-size fluctuations during fractures and vugs formation, due to fines migration. 2022 The Authors Open Access funding provided by the Qatar National Library . This research was made possible by the National Priorities Research Program (NPRP) (grant # NPRP8-594-2-244 ) and the Graduate Sponsorship Research Award (GSRA) (grant # GSRA7-1-0217-20002 ) from Qatar National Research Fund (a member of Qatar Foundation ). The findings achieved herein are solely the responsibility of the authors. The SMT images were collected using the X-ray Operations and Research Beamline Station 13-BMD at Argonne Photon Source (APS), Argonne National Laboratory. The authors thank Dr. Mark Rivers of APS for help in performing the SMT scans. The authors thank Dr. Wadi Imseeh for his help in performing the SMT scans. The authors also acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is supported by the National Science Foundation , USA, Earth Sciences ( EAR-1128799 ), and the US Department of Energy (DOE) , Geosciences ( DE-FG02-94ER14466 ). Use of the Advanced Photon Source, an Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory , was supported by DOE , USA under (contract no. DE-AC02-06CH11357 ). The authors thank the reviewers for their suggestions and constructive comments that helped improve and enhance the manuscript. Scopus

Sustainable bioelectrogenesis was evaluated by oxidizing the organics of food waste leachate (FWL) under the influence of magnetic field (MF) and short term applied voltage (electric potential, EP). Adaptation of MF (20–220 m T) and EP (100−500 mV) had enhanced the performance of MFC in terms of power generation and reduction of organic in FWL. The best performance of MFC was noted with a MF at 220 m T and EP at 500 mV. MFC under the influence of applied EP (100−500 mV), the power generation was increased from 493 mW/m2 to 832 mW/m2. During this operation, the chemical oxygen demand removal (CODr) was also increased from 51.3 % to 80.4 %. Whereas the control MFC (MFC-C) had exhibited a maximum power generation and CODr of 224 mW/m2 and 36.3 %, respectively. MFC with MF has showed an increase in power density from 480 mW/m2 to 811 mW/m2. MFCs at 220 m T and 500 mV has exhibited, 262 % and 271 % increase in power density over control, respectively. Adaptation of MFC under the EP and MF were found to be beneficial in treating FWL which has high strength organic content.

Gas production studies from natural gas hydrate reservoirs have been the subject of extensive research in recent years. Although CH4-CO2 replacement production method from gas hydrates has many advantages, the number of the studies related to this production method are less than depressurization production method studies, especially in microscale porous media. Hence, this paper presents a comprehensive literature review on CH4-CO2 replacement to better understand the associated processes and mechanisms in microscale porous media with emphasis on micromodel experiments, 3D imaging, other visualization testing method and pore network modelling. Moreover, the advantages and disadvantages of currently available CH4-CO2 replacement studies were investigated. The critical issues of the replacement method were underlined and new suggestions have been offered for future investigations.

CH4-CO2 replacement method has the advantages of sequestering carbon dioxide and sediment stability compared to other methods such as depressurization and thermal stimulation. However, the production efficiency using CH4-CO2 replacement method is lower than any other method. In this study, effects of soaking process on CH4-CO2 replacement efficiency were determined. The soaking process was the time to close all valves for the enhancement of CH4-CO2 reaction which resulted in the long reaction time between the injected CO2 and methane hydrate and consisted of the 1st and the 2nd production with soaking time after dynamic replacement. Results showed that total replacement efficiency increased with increasing number of soaking processes and more soaking time. The increasing rate of replacement efficiency in the first soaking process was higher than that in the second process. However, the soaking process showed the disadvantage that the total production time increased with increasing soaking time and process, which could result in the production cost increase. Therefore, appropriate soaking time and number of soaking processes are required to improve the replacement efficiency considering production cost. 2020 The Authors This research was made possible by an NPRP grant # NPRP8-594-2-244 from the Qatar National Research Fund (a member of Qatar Foundation ). And this work was supported by the National Research Foundation of Korea( NRF ) grant funded by the Korea government ( MSIT ) ( 2020R1A2C101235211 ). Also, this research was partially supported by the Ministry of Trade, Industry, and Energy ( MOTIE ) through the Project "Gas Hydrate Exploration and Production Study ( 20-1143 )" under the management of the Gas Hydrate Research and Development Organization (GHDO) of Korea and the Korea Institute of Geoscience and Mineral Resources (KIGAM). Also, this research was supported by a grant ( 2018-MOIS31-009 ) from Fundamental Technology Development Program for Extreme Disaster Response funded by Korean Ministry of Interior and Safety (MOIS). Scopus

Petroleum hydrocarbon (PHC) contamination is a global environmental issue. Understanding the key factors and mechanisms controlling the fate and mobility of PHCs in soils and aquifers is critical for environmental risk assessment, the development of remediation strategies, and policy decisions. This study focuses on the effects of soil composition and temperature on the sorption and desorption of two representative aromatic PHC compounds: benzene and naphthalene. The experiments were carried out using artificial sandy loam soil mixtures with temperatures ranging from 3 to 25℃. As expected, the sorption capacities of the soils were primarily controlled by the organic carbon (OC) content, while barely affected by the clay content. The sorption data for benzene and naphthalene followed linear to near-linear isotherms. Naphthalene sorption further increased with decreasing temperature, whereas temperature had little effect on benzene sorption. The latter was consistent with the very small magnitude of the sorption enthalpy of benzene. Under imposed dynamic temperature fluctuations, naphthalene sorption and desorption were shown to be reversible: model simulations demonstrated minimal kinetic limitation of the temperature-dependent soil-water partitioning. Our results imply that even in simple artificial soil systems, temperature variations can have complex, but predictable, effects on the soil-pore water partitioning of PHCs and, hence, on their mobility and bioavailability. Understanding the role of temperature is thus a prerequisite to unraveling the coupled abiotic and biotic processes that modulate the fate of PHCs in real-world soils.

The critical state (CS) concept is a theoretical framework that models the constitutive behavior of soils, including sand and other granular materials. It supports the notion of a unique postfailure state, where the soil ultimately experiences continuous shearing with no change in the plastic volumetric strain. However, the published literature has frequently noted the nonconvergence of sand specimens with different initial densities to a unique CS in the compression plane due to many factors such as specimen fabric, particle morphology, breakage, and grain size distribution. This paper examines the CS for poorly graded (uniform) glass beads and 3 different types of silica sands using 50 conventional triaxial compression (CTC) experiments, 12 oedometer tests, and in situ synchrotron microcomputed tomography (SMT) scans for 10 CTC experiments. The results of the 50 CTC experiments revealed a diffused CS zone in the compression plane, which was further examined using the in situ SMT scans. A thorough three-dimensional image analysis of the SMT scans accurately quantified the evolution of the local void ratio (elocal ) versus axial compression within zones of intensive shearing toward the center of the specimen. The evolution of the void ratio was also measured using the entire volume of the specimen (eglobal ). At the CS, the elocal/eglobal ratio was assessed to be ∼1.25 when a single shear band developed within the scanned specimens and ∼1.1–1.15 for specimens that failed via external bulging that was internally manifested by the development of multiple shear bands. This finding suggests that the CS zone in the compression plane can be attributed to the common wrong consideration of eglobal evolution in lieu of elocal within the developing shear bands. Furthermore, the lack of shear band development in uniaxial compression has made the results of the oedometer test reliable in quantifying the CS parameters in the compression plane. This material was partially funded by the US National Science Foundation (NSF) under Grant CMMI-1266230. Any opinions, findings, conclusions, and recommendations expressed in this paper are those of the authors and do not necessarily reflect the views of the NSF. The SMT scans presented in this paper were collected using the X-Ray Operations and Research Beamline Station 13-BMD of the Advanced Photon Source (APS), a US Department of Energy (DOE) Office of Science User Facility operated by the Argonne National Laboratory (ANL) under Contract DE-AC02-06CH11357. We acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is funded by the NSF Earth Sciences (EAR-1128799), and the DOE Geosciences (DE-FG02-94ER14466). We thank Dr. Mark Rivers for his guidance at APS. Scopus

Recent research showed that fracture of sand particles plays a significant role in determining the plastic bulk volumetric changes of granular materials under different loading conditions. One of the major tools used to better understand the influence of particle fracture on the behavior of granular materials is discrete-element modeling (DEM). This paper employed the bonded block model (BBM) to simulate the fracture behavior of sand. Each sand particle is modeled as an agglomerate of rigid blocks bonded at their contacts using the linear-parallel contact model, which can transmit both moment and force. DEM simulated particles closely matched the actual three-dimensional (3D) shape of sand particles acquired using high-resolution 3D synchrotron microcomputed tomography (SMT). Results from unconfined one-dimensional (1D) compression of a single synthetic silica cube were used to calibrate the model parameters. Particle fracture was investigated for specimens composed of three sand particles that were loaded under confined 1D compression. Breakage energy measured from DEM models matched well with that measured experimentally. The paper studied the effects of contact loading condition and particle interaction on the fracture mode of particles using BBM that can closely capture the 3D shape of real sand particles. 2020 This work is made available under the terms of the Creative Commons Attribution 4.0 International license,. This material is partially funded by the US National Science Foundation (NSF) under Grant No. CMMI-1362510. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF. The authors thank Dr. Mehmet Cil for conducting sand-column experiments, and Dr. Andrew Druckrey for conducting cube-fracture experiments. The SMT images were collected using the X-ray Operations and Research Beamline Station 13-BMD at Argonne Photon Source (APS), Argonne National Laboratory. The authors thank Dr. Mark Rivers of APS for help in performing the SMT scans. They also acknowledge the support of GeoSoilEnviro-CARS (Sector 13), which is supported by the National Science Foundation, Earth Sciences (EAR-1128799), and the US Department of Energy (DOE), Geosciences (DE-FG02-94ER14466). Use of the Advanced Photon Source, an Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory, was supported by DOE under Contract No. DE-AC02-06CH11357. The authors also thank the anonymous reviewers who contributed comments and suggestions to improve this paper. Scopus

The developing approaches in the recovery of resources from biowastes for the production of renewable value-added products and fuels, using microbial cultures as bio-catalyst have now became promising aspect. In the path of anaerobic digestion, the microorganisms are assisting transformation of a complex organic feedstock/waste to biomass and biogas. This potentiality consequently leads to the production of intermediate precursors of renewable value-added products. Particularly, a set of anaerobic pathways in the fermentation process, yields small-chain fatty acids (SCFA), and medium-chain fatty acids (MCFA) via chain elongation pathways from waste valorization and CO

Most of the prediction theories regarding dissolution of organic contaminants in the subsurface systems have been proposed based on the static water conditions and the influence of water fluctuations on mass removal requires further investigations. In this study, it was intended to investigate the effects of water table fluctuations on biogeochemical properties of the contaminated soil at the smear zone between the vadose zone and the groundwater table. An automated 60 cm soil column system was developed and connected to a hydrostatic equilibrium reservoir to impose the water regime by using a multi-channel pump. Four homogenized hydrocarbon contaminated soil columns were constructed and two of them were fully saturated and remained under static water conditions while another two columns were operated under water table fluctuations between the soil surface and 40 cm below it. The experiments were run for 150 days and relevant geochemical indicators as well as dissolved phase concentrations were analyzed at 30 and 50 cm below the soil surface in all columns. The results indicated significant difference in terms of biodegradation effectiveness between the smear zones exposed to static and water table fluctuation conditions. This presentation will provide an overview of the experimental approach, mass removal efficiency, and key findings. This publication was made possible by funding from NPRP grant # NPRP9-093-1-021 from the Qatar national research fund (a member of Qatar Foundation). We acknowledge that all the Gas Chromatography analyses were accomplished in the Central Laboratories unit, Qatar University.

CH4-CO2 replacement has been considered as a method for methane production from hydrate-bearing sediments to maintain sediment stability. Sediment stability has been studied at both the particle scale and mesoscale. However, the shear stiffness of sediments has not yet been explored. Moreover, the effects of CO2 and CO2-N2 mixtures as injection fluids on sediment stability remain unclear. Thus, this study aimed to determine the variations in shear wave velocity and electrical resistivity during hydrate formation, CH4-CO2 replacement, and hydrate dissociation using two types of injecting fluids (CO2 and CO2-N2 mixture). The results demonstrated that hydrate-bearing sediment could maintain its stability during CH4-CO2 replacement by injecting CO2 or CO2-N2 mixture. Furthermore, injecting CO2-N2 mixture was more efficient for methane production than injecting CO2. The Results also revealed that injecting CO2-N2 mixture could lead to higher stability of sediments during CH4-CO2 replacement than injecting CO2, although the difference in sediment stability was small between the two cases. 2020 The Author(s) This research was mainly supported by NPRP grant #NPRP8-594-2-244 from the Qatar National Research Fund (a member of the Qatar Foundation ). This research was partially supported by the Ministry of Trade, Industry, and Energy ( MOTIE ) through the Project "Gas Hydrate Exploration and Production Study (20-1143)" under the management of the Gas Hydrate Research and Development Organization (GHDO) of Korea and the Korea Institute of Geoscience and Mineral Resources ( KIGAM ). This research is also supported by "Study on Submarin Active Faults and Evaluation of Possibility of Submarine Earthquakes in the Southern Part of the East Sea, Korea (20-9850)" of the Ministry of Ocean and Fisheries. The findings achieved herein are solely the responsibility of the authors. Scopus

Recently, researchers have been attracted towards the gas production from hydrate bearing sediments considering its abundance in marine continental margins and persisting demand for alternate energy. Dissociation of hydrate into gas and water is the preliminary technique for gas production in hydrate bearing sediments. Expanded fluid volume and gas pressure upon dissociation detach the fines from the grain surface and result in pore throat entrapment. Migration of fines associated with gas flow greatly influence the alteration of permeability of the sediment by clogging pore throats in the flow path. A pore-scale visualization study was implemented to provide a clear insight into the actual mechanisms associated with mobilization and clogging of fines during two-phase flow through a microfluidic chip. Carboxylate modified polystyrene latex particles deposited in the porous media were migrated during drainage with CO2 gas. The detachment of fine particles from the grain surfaces was observed and were retained on the new interface; gas-water interface. The images and videos captured during the experiment were helpful in observing additional pore scale mechanisms responsible for permeability impairment in the porous media. Interface pinning, deformation and resistance to coalescence were found to be other mechanisms in addition to pore clogging.

Production of methane from hydrate-bearing sediments requires hydrate dissociation for releasing mobile methane gas in sediments prior to gas production operations. Fines may migrate through or clog the pore space of sandy sediments depending on the geometry and topology of the pore space. Multiphase flow experiments were conducted on brine saturated uniform silica sand mixed with different percentages of kaolinite. Fines concentrations were correlated to computed tomography (CT) numbers in their host brine phase. Representative element volume (REV) procedure was used to study local porosity and local fines concentration. A cubical REV with a side length of 850 µm was selected. For low fines content (less than 6%), gas percolated through the specimens with no major particle translation or porosity change. For 6% kaolinite specimen, fractures were initiated, and propagated by densifying surrounding sediments. Local fines concentration study showed that fines migrated through the pores for specimens with fines content less than 6%. For the 6% kaolinite specimen, fines concentrated near fractures due to clogging. Clogging induced an increase in the capillary pressure at the pore throats and caused the capillary pressure to overcome the effective stress between sand particle, and fractures to be initiated. Sand particles experienced up to 200 µm translation and 15◦ rotation due to gas driven fracture in the 6% kaolinite specimen This research was made possible by the National Priorities Research Program (NPRP) grant # NPRP8-594-2-244 from Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors. The SMT images were collected using the X-ray Operations and Research Beamline Station 13-BMD at Argonne Photon Source (APS), Argonne National Laboratory. The authors thank Dr. Mark Rivers of APS for help in performing the SMT scans. They also acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is supported by the National Science Foundation , USA, Earth Sciences ( EAR-1128799 ), and the US Department of Energy (DOE) , Geosciences ( DE-FG02-94ER14466 ). Use of the Advanced Photon Source, an Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory, was supported by DOE , USA under contract no. DE-AC02-06CH11357 . Scopus

Release of deposited colloids in the soil porous media during two-phase flow poses potential health hazard due to the facilitated transport of contaminants towards groundwater reservoirs. Considerable uncertainties exist concerning the impact of ionic strength on pore-scale mechanisms of colloid mobilization during transient flow. This study aims to investigate the effect of ionic strength on colloid retention and mobilization using a glass micromodel. The behavior of Carboxylate modified Polystyrene latex particles of 5 ?m diameter in saline solution (i.e., 100 mM & 1 mM of NaCl at pH 10) was visualized with an optical microscope during saturated and twophase flow. We found that colloid aggregation and attachment on Solid-Water Interfaces (SWI) was increased with increase in ionic strength. CO2 injection into the saturated micromodel mobilized the previously attached colloids on SWI, retained at the Gas- Water Interfaces (GWI) due to capillary forces and thus were transported through the micromodel. Imbibition mobilize colloids from GWI and are transported or reattached on SWI depending on the ionic strength of pore water. The greater adhesive forces of colloids at higher ionic strength was resulted in thin film attachment during drainage and reattachment of colloids mobilized from GWI on SWI during imbibition. The acquired images showed the application of a micromodel for the visualization of colloid retention and re-mobilization through the porous media. This publication was made possible by partial funding from NPRP grant # NPRP8- 594-2-244 from the Qatar National Research Fund (a member of Qatar Foundation). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of funding agencies.

Formation damage costs oil and gas industry $140 billion/year in lost productivity, this is a key challenge to Qatar, the world's largest LNG exporter. During production from a well, multiphase flow foster drag forces to mobilize fine particles from within the subsurface. Fine' migration can alter the gas flow, clogging pores and disconnecting gas pathways. Understanding fines influence is a complex challenge due to the reservoirs' porous media heterogeneity. Microtomography of sand sediments provides a standardized approach to study the fines impact. X-Ray microtomography of two repacked sand cylinders was carried at Argonne National Lab synchrotron. Rounded silica sand was mixed with hydrophilic swelling montmorillonite clay. High and low fines concentrations were mix--ed with the sand then deposited into five layers. Initially, samples were fully saturated, then gas was injected, the sediments were scanned before and after injection. At first, fines were suspended in the brine, but after injection were retained on the gasbrine interface, and their concentration in the brine increased. Gas injection divided pores and throats, reducing their average size. Contrarily, main gas pathways increased in size but were disconnected in the sediment with high fines concentration. Fines caused increased capillary pressure and lowered the sediment permeability. This research was made possible by the National Priorities Research Program (NPRP) grant #NPRP8-594-2-244 from Qatar national research fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors. The SMT images were collected using the X-ray Operations and Research Beamline Station 13-BMD at Argonne Photon Source (APS), Argonne National Laboratory. The authors thank Dr. Mark Rivers of APS for help in performing the SMT scans. They also acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is supported by the National Science Foundation, USA, Earth Sciences (EAR-1128799), and the US Department of Energy (DOE) and Geosciences (DE-FG02-94ER14466). Use of the Advanced Photon Source, an Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory, was supported by DOE, USA under contract no. DE-AC02-06CH11357.

A novel cellobiohydrolase (CBH)-generating fungi have been isolated and categorized as Schizophyllum commune KMJ820 based on morphology and rDNA gene sequence. Cellulose powder was used as carbon source, the total enzyme activity was 11.51 U/ml is noted; which is among the highest amounts of CBH-generating microbes studied. CBH have been purified to homogenize, with pursual of serial chromatography using S. commune supernatants and two different CBHs were found; CBH 1 and 2. The filtered CBHs showed greater activity (V(max) = 51.4 and 20.8 U/mg) in contrast to CBHs from earlier studies. The MW (molecular weights) of S. commune CBH 1 and 2 were verified to be approximately 50 kDa and 150 kDa, respectively, by size exclusion chromatography. Even though CBHs have been evaluated from other sources, but S. commune CBH is prominent in comparison to other CBHs by its high enzyme activity. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s12088-019-00843-9) contains supplementary material, which is available to authorized users.

It is well known that the constitutive behaviour of granular materials is influenced by strain localisation into zones of intensive shearing, known as shear bands. The failure mode of specimens tested under axisymmetric triaxial compression is commonly manifested through single or multiple shear bands, or diffuse bifurcation (bulging). The ability to monitor and detect the evolution of strain localisation has been enhanced by measuring particle kinematics using discrete-element methods or three-dimensional imaging techniques such as X-ray computed tomography. However, conventional particle kinematic techniques cannot expose intricate localised shearing during the hardening, before the peak principal stress ratio. This paper presents the concept of particle translation gradient to expose strain localisation in granular materials using experimental measurements of particle translation in three dimensions. Individual silica sand particles were identified and tracked through multiple strains and particles' translations were calculated. Each particle's neighbouring particles were identified and translation fields for each of the neighbouring particles were calculated. The second-order norms between a particle translation vector and the neighbouring particles' translation vectors were averaged, resulting in a relative translation value for each particle. The translation gradient concept is effective in uncovering the onset of strain localisation within sheared granular materials. ACKNOWLEDGEMENTS This material is partially funded by the US National Science Foundation (NSF) under grant no. CMMI-1266230 and Office of Naval Research (ONR) grant no. N00014-11-1-0691. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF or ONR. The SMT images presented in this paper were collected using the X-Ray Operations and Research Beamline Station 13-BMD at Argonne Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science user facility operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357. The authors acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is supported by the National Science Foundation � Earth Sciences (EAR-1128799), and the Department of Energy, Geosciences (DE-FG02-94ER14466). They also thank Dr Mark Rivers of APS for help in performing the SMT scans. Scopus

Tortuosity is a parameter that plays a significant role in the characterization of complex porous media systems and it has a significant impact on many engineering and environmental processes and applications. Flow in porous media, diffusion of gases in complex pore structures and membrane flux in water desalination are examples of the application of this important micro-scale parameter. In this paper, an algorithm was developed and implemented as a MATLAB code to compute tortuosity from three-dimensional images. The code reads a segmented image and finds all possible tortuous paths required to compute tortuosity. The code is user-friendly, easy to use and computationally efficient, as it requires a relatively short time to identify all possible connected paths between two boundaries of large images. The main idea of the developed algorithm is that it conducts a guided search for connected paths in the void space of the image utilizing the medial surface of the void space. Once all connected paths are identified in a specific direction, the average of all connected paths in that direction is used to compute tortuosity. Three-dimensional images of sand systems acquired using X-ray computed tomography were used to validate the algorithm. Tortuosity values were computed from three-dimensional images of nine different natural sand systems using the developed algorithm and compared with predicted values by models available in the literature. Findings indicate that the code can successfully compute tortuosity for any unconsolidated porous system irrespective of the shape (i.e., geometry) of particles. 1 2017 Elsevier B.V. Scopus

Fine particles within porous media may migrate with the flowing fluid and cause bridging or clogging in the pore space. Bridging and clogging reduce the flow permeability of porous media, which has a significant influence on petroleum engineering applications such as water and oil extraction, sand production, and gas production from hydrate-bearing sediments. Although the migration of fine particles and its impact on bridging and clogging have been investigated for a single-phase flow, it has not been understood clearly for a multi-phase flow. This work reports an approach using microfluidic pore models to study the migration of fine particles and the bridging/clogging behavior in a structure mimicking porous media. Results from the microfluidic model show that: (1) fine particles accumulated along the water and gas (CO2) interface; (2) fine particle concentrations in pores locally increased due to the accumulated particles at the interface, and (3) consequently bridging and clogging occurred in the pore throat. Findings from this work provide a starting point in understanding complex phenomena including a reduced flow permeability of porous media on a fluid containing fine particles for a variety of petroleum engineering applications. 2017, Springer-Verlag GmbH Germany. Acknowledgement This research was made possible by NPRP Grant # NPRP8-594-2-244 from Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors. Scopus

A pristine soil environment supports a healthy soil biodiversity, which is often polluted with recalcitrant compounds. The bioelectrochemical remediation of the contaminated soils using bioelectrochemical systems (BESs) is gaining significant attention with respect to the restoration of the soil ecosystem. In this direction, a microbial fuel cell (MFC, an application of BES), was employed for the treatment of total petroleum hydrocarbons (TPHs) in a soil microenvironment at three ranges of pollution (loading conditions-320, 590 and 840 mg TPH per L). TPHs degraded effectively in the soil-electrode vicinity in the range of 158 mg TPHR per L (320 mg TPH per L) and 356 mg TPHR per L (840 mg TPH per L). The study also demosntrated a maximum bioelectrogenesis of 286.7 mW m-2 (448 mV at 100 ) at the highest TPH loading concentration studied (840 mg TPH per L). The conditions prevailing in the soil MFC also facilitated the removal of sulfates (114 mg SO42- per L; 62.64%) and the removal of total dissolved solids (910 mg TDS per L, 12.08%) at an 840 mg TPH per L loading condition. The pH of the outlet wastewater prevailing in the mild alkaline range of 7.6 and 8.4, along with improved sulfate and TPH removal in the respective conditions suggested suitable conditions for sulfate-reducing bacteria (SRB). This study also signified the sustainability of the process for the effective treatment of hydrocarbon contaminated soil that also generates green energy. This publication was made possible by NPRP grant # NPRP9-093-1-021 from the Qatar National Research Fund (a member of Qatar Foundation). Scopus

Produced water (PW) is a wastewater generated in large quantities from the extraction of oil and gas. PW found to have high amounts of dissolved solids (TDS) and residual petroleum hydrocarbons causing considerable damage to the environment. PW also contains sulfates in significant amounts, due to which treating this wastewater is essential prior to discharge. The present study was aimed for bioelectrochemical treatment of PW and simultaneous bioelectrogenesis in the two most studied configurations viz., single and dual chamber microbial fuel cells (MFCs). The study evidenced treatment of recalcitrant pollutants of PW. Both MFCs were operated by keeping similar operating conditions such as anode chamber volume, hydraulic retention time (HRT) for batch mode of operation, electrode materials, inlet characteristics of PW and ambient temperature. Among both configurations, dual chamber MFC showed higher efficiency with respect to bioelectrogenesis (single chamber - 789 mW/m 2 ; dual chamber - 1089 mW/m 2 ), sulfates removal (single chamber - 79.6%; dual chamber - 93.9%), total petroleum hydrocarbons removal (TPH, single chamber - 47.6%; dual chamber - 53.1%) and chemical oxygen demand degradation (COD, single chamber - 0.30 kg COD/m 3 -day (COD removal efficiency, 54.7%); dual chamber - 0.33 kg COD/m 3 -day (COD removal efficiency, 60.2%)). Evaluated polarization behavior of both MFCs were also evidenced the effective response of the electroactive anodic biofilm. 2019 Elsevier B.V. This publication was made possible by NPRP grant # NPRP9-093-1-021 from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors. Scopus

Recently, researchers are attracted towards the gas production from hydrate bearing sediments considering its abundance in marine continental margins and persisting demand for alternate energy. Dissociation of hydrate into gas and water is the preliminary technique for gas production in hydrate bearing sediments. Expanded fluid volume and gas pressure upon dissociation detach the fines from the grain surface and result in pore throat entrapment. Migration of fines associated with gas flow greatly influence the alteration of permeability of the sediment by clogging pore throats in the flow path. A pore-scale visualization study was implemented to provide a clear insight into the actual mechanisms associated with mobilization and clogging of fines during two-phase flow through a microfluidic chip. Carboxylate modified polystyrene latex particles deposited in the porous media were migrated during drainage with CO2 gas. The detachment of fine particles from the grain surfaces was observed and were retained on the new interface; gas-water interface. The images and videos captured during the experiment was helpful in observing additional pore scale mechanisms responsible for permeability impairment in the porous media. Interface pinning, deformation and resistance to coalescence was found to be other mechanisms in addition to pore clogging. EAGE 2019. This research was partially funded by National Priority Research Program (NPRP) grant # NPRP8-594-2-244 from Qatar National Research Fund (a member of Qatar Foundation). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of funding agencies. Scopus

Recent studies have shown that detection of the onset and evolution of micro shear bands (MSBs) in granular materials can be improved using measurements of the kinematic behavior of particles. Different methods such as the discrete-element method (DEM) or threedimensional (3D) imaging techniques have been used to measure the kinematics of individual particles within triaxial specimens. However, conventional kinematic techniques that use particle translation and/or rotation cannot detect the onset and growth of MSBs during the hardening phase of axisymmetric triaxial experiments. In order to expose the localized shearing and particle-scale behavior of triaxial specimens, a relative particle translation gradient (RPTG) concept is used to detect and expose the onset of strain localization before the peak principal stress ratio (PSR). RPTG measurements for four different granular materials are reported in this paper. The RPTG concept is used to expose the onset of MSBs during the hardening phase of the experiments. In addition, the contact number of individual particles is quantified and discussed in relation to particle rotation to investigate a particle-scale relationship between particle contacts and rotation. The effects of density, confining pressure, and particle shape on contact number are examined. The research is funded by the US National Science Foundation (NSF) under Grant Nos. CMMI-1266230 and CMMI-1362510. Any opinions, findings, and conclusions or recommendations expressed in this paper are those of the authors and do not necessarily reflect the views of the NSF. The SMT images presented in this paper were collected using the X-Ray Operations and Research Beamline Station 13-BMD at Argonne Photon Source (APS), a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The authors acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is supported by NSF-Earth Sciences (EAR-1128799), and DOE, Geosciences (DE-FG02-94ER14466). The authors thank Dr. Mark Rivers of APS for help performing the SMT scans. Scopus

Methane hydrates are promising unconventional energy source with natural reserves above 1,000 Trillion m3. Hydrates are found in saturated sandy sediments, where multi-phase flow of gas takes place through sediment's pores, physical phenomenon at pore-scale controls flow properties. Gas permeability is highly affected by fines type due to migration, clogging and bridging reducing gas flow. Fines migration has huge influence on storage and recovery of oil and gas resources from the subsurface. There is a knowledge gap of fines effects on gas production from sandy sediments, especially at pore-scale, in homogenous porous media. Therefore, there is a need to model and quantify fines impact on multi-phase flow using 3D reconstruction to better understand gas recovery systems. The pores in which gas flow through are reconstructed using 3D synchrotron X-ray micro- computed tomography images of sand sediments, at resolution of 3.89 micron per voxel. Sand was mixed with fines and deposited in test columns. Kaolinite and Montmorillonite clay fine particles were added in different columns, each system was scanned at four stages with varied saturations of brine as CO2 gas was injected in real time while scanning. Images were processed for 3D visualization, segmentation and quantification for each system. Effects of swelling and non-swelling clays were characterized to understand multi-phase flow of gas at pore-scale. Findings revealed that fines accumulate at sand-brine and brine-gas interfaces. As fines concentration increased, gas percolation decreased. Further increase in fines concentrations resulted in blocking local gas flow causing pressure variations enough to create fractures that allows gas to escape and percolation to rise. In unconsolidated media, the pore space geometry will change due to sand grains movements. At high concentrations, different fines types produce altered gas flow regimes, Kaolinite which is non-swelling clay resulted in fractures while montmorillonite which is swelling resulted in detached gas ganglia entrapping the gas. Generally, increasing fines reduces gas percolation and further injection of gas reduced permeability. The finds herein are critical in understanding the impact of fines migration during gas flow in sand, they can be applied to characterizing and predicting two phase properties of unconsolidated sediments. The qualitative and quantitative findings achieved in this work in 3D, agree with other observations in recent literature on 2D micromodels. Understanding the fluid physics in homogenous sand systems is an essential step to quantify fines impact on heterogeneous rock systems. The work helps in improving flow characterizing at pore scale, to mitigate to formation damage problem and advance reservoirs upscaling capabilities. Copyright 2019, Society of Petroleum Engineers. This research was made possible by the National Priorities Research Program (NPRP) grant #NPRP8-594-2-244 from Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors. The SMT images were collected using the X-ray Operations and Research Beamline Station 13-BMD at Argonne Photon Source (APS), Argonne National Laboratory. The authors thank Dr. Mark Rivers of APS for help in performing the SMT scans. They also acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is supported by the National Science Foundation, USA, Earth Sciences (EAR-1128799), and the US Department of Energy (DOE), Geosciences (DE-FG02-94ER14466). Use of the Advanced Photon Source, an Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory, was supported by DOE, USA under contract no. DE-AC02-06CH11357. Scopus

Availability of natural hydrates and ongoing rise in demand for energy, motivated researchers to consider hydrates as a potential energy source. Prior to gas production operations from hydrate-bearing sediments, hydrate dissociation is required to release gas into sediments. To reliably predict natural hydrate reservoir gas production potential, a better understanding of hydrate dissociation kinetics is needed. Hydrate dissociation models assume the relationship between hydrate surface area and (hydrate volume)2/3 to be linear due to hydrate sphericity assumptions. This paper investigates the validity of the spherical hydrate assumption using in-situ three-dimensional (3D) imaging of Xenon (Xe) hydrate dissociation in porous media with dynamic 3D synchrotron microcomputed tomography (SMT). Xe hydrate was formed inside a high-pressure, low-temperature cell and then dissociated by depressurization. During dissociation, full 3D SMT scans were acquired continuously and reconstructed into 3D volume images. A combination of cementing, pore-filling, and surface coating pore-habits were observed in the specimen. It was shown that hydrate surface area can be estimated using a linear relationship with (hydrate volume)2/3 during hydrate dissociation in porous media based on direct observations and measurements from 3D SMT images. EAGE 2019. Funding was partially provided by National Priority Research Program (NPRP) grant # NPRP8-594-2-244 from Qatar National Research Fund (a member of Qatar Foundation) and the Institute for a Secure and Sustainable Environment (ISSE), University of Tennessee-Knoxville, USA. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of funding agencies. This paper used resources of the Advanced Photon Source (APS),a U.S.DepartmentofEnergy(DOE) Office of Science User Facilitypoerated for the DOE Office of Science by Argonne National Laboratory (ANL) under Contract No. DE-AC02-06CH11357. The SMT images presented in this paper were collected using the x-ray Operations and Research Beamline Station 13-BMD at Argonne Photon Source (APS), ANL. We thank Dr. Mark Rivers of APS for help in performing the SMT scans. We also acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is supported by the National Science Foundation, Earth Sciences (EAR-1128799), and the DOE, Geosciences (DE-FG02-94ER14466). Scopus

Carbon sequestration in geological formations is in demand for many applications, especially energy production from hydrates. During gas production in a sandy hydrate reservoir, two phase flow and changes in confinement takes place. Nine fully saturated sand systems were scanned three times; before, during and after CO2 gas injection. The confinement pressure was altered, by placing a vertical spring that presses against the upper port of the sediment cylinder. 3D images were analyzed by direct visualization, followed by quantification and pore network analysis. Outcomes demonstrated that shape of sand particles affects how the unconsolidated media will impact the flow, in angular sediments with high confinement pressure, there is more friction between the grains, this results in no dislocations of sand, the fines clog the throats, and more formation damage is noted. In rounded grains with lower confinement pressure, sand grains dislocated; opening large pathways for gas flow; this resulted in lower formation damage. Measures done using pore networks, showed that because of micro-fractures, permeability of the system can increase during hydrate production. This is in contrast to the other systems, where throat sizes shrunk, decreasing the permeability; because of fines migration toward the throats and the small sand grains dislocations. EAGE 2019. This research was made possible by the National Priorities Research Program (NPRP) grant #NPRP8-594-2-244 from Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors. The SMT images were collected using the X-ray Operations and Research Beamline Station 13-BMD at Argonne Photon Source (APS), Argonne National Laboratory. The authors thank Dr. Mark Rivers of APS for help in performing the SMT scans. They also acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is supported by the National Science Foundation, USA, Earth Sciences (EAR-1128799), and the US Department of Energy (DOE), Geosciences (DE-FG02-94ER14466). Use of the Advanced Photon Source, an Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory, was supported by DOE, USA under contract no. DE-AC02-06CH11357. Scopus

Particle morphology, orientation, and contact configuration play a significant role in the engineering properties of granular materials. Accurate three-dimensional (3D) characterization of these parameters for experiments has historically proven difficult, especially in the context of particle contact with small particle size. This paper describes a computer code that was developed to analyze 3D images of granular materials to measure particle lengths (size), volume, surface area, global centroid location and orientation; it also provides a method to calculate particle contact location and orientation. Measurements from the proposed code can define a state of the granular material's fabric that can be used as input for micro-mechanics based constitutive models and to validate numerical discrete element simulations. A fabric tensor and its evolution is calculated based on experimental contact normal vectors that were extracted from SMT imaging of an axisymmetric triaxial compression experiment on a natural silica sand known as F-35 sand. This material is partially funded by the US National Science Foundation (NSF) under Grant No. CMMI-1266230 and Office of Naval Research (ONR) Grant No. N00014-11-1-0691 . Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF or ONR. This paper used resources of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory (ANL) under Contract No. DE-AC02-06CH11357. The SMT images presented in this paper were collected using the X-ray Operations and Research Beamline Station 13-BMD at Argonne Photon Source (APS), ANL. We thank Dr. Mark Rivers of APS for help in performing the SMT scans. We also acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is supported by the National Science Foundation, Earth Sciences ( EAR-1128799 ), and the DOE, Geosciences ( DE-FG02-94ER14466 ). Scopus

A better understanding of the kinetics of hydrate dissociation is essential to reliably predict gas production potential from natural hydrate reservoirs. Most hydrate dissociation models assume hydrates to be a constant number of equal-sized spheres dissociating at a constant rate. This paper uses dynamic 3D synchrotron micro-computed tomography (SMT) imaging to study hydrate surface area evolution during Xenon hydrate dissociation. Hydrates are formed inside a high-pressure low-temperature cell filled with partially saturated ASTM 20-30 Ottawa sand. Hydrate dissociation is initiated through depressurization in the first experiment and through thermal stimulation in the second experiment. During dissociation, continuous full 3D SMT images were acquired where each scan took 45 s to complete. A combination of cementing, pore-filling, and surface coating pore habits were observed for the depressurization experiment and pore-filling for the thermal stimulation experiment. Surface coating hydrates dissociate faster than hydrates with pore-filling pore habit due to the higher specific area which allows for more surface for hydrates to dissociate it. Direct measurements of hydrate volume and hydrate surface area suggest that even with a combination of hydrate pore habits formed within the 3D porous media, estimation of hydrate surface area as a linear relation with (hydrate volume)2/3 is best for hydrate saturation less than a threshold value depending on the dissociation method and driving force. (hydrate volume)2 and (hydrate volume)3 were found to better estimate hydrate interfacial area in comparison to (hydrate volume)2/3 for the depressurization experiment and thermal stimulation experiment, respectively. 2019 The Authors This publication was made possible by partial funding from NPRP grant # NPRP8-594-2-244 from the Qatar national research fund (a member of Qatar Foundation) and the Institute for a Secure and Sustainable Environment (ISSE) , University of Tennessee-Knoxville, USA . Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of funding agencies. The authors would like to thank Mr. Wadi Imseeh for his help during scanning and Mr. Jamal Hannun for his help in interfacial area analysis. This paper used resources of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory (ANL) under Contract No. DE-AC02-06CH11357. The PSMT images presented in this paper were collected using the x-ray Operations and Research Beamline Station 13-BMD at Argonne Photon Source (APS), ANL. We thank Dr. Mark Rivers of APS for help in performing the PSMT scans. We also acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is supported by the National Science Foundation, Earth Sciences (EAR-1128799), and the DOE, Geosciences (DE-FG02-94ER14466). The authors would also like to thank the anonymous reviewers who contributed with comments and suggestions to improve this paper. Scopus

The availability of natural gas hydrates and the continuing increase in energy demand, motivated researchers to consider gas hydrates as a future source of energy. Fundamental understanding of hydrate dissociation kinetics is essential to improve techniques of gas production from natural hydrates reservoirs. During hydrate dissociation, bonds between water (host molecules) and gas (guest molecules) break and free gas is released. This paper investigates the evolution of hydrate surface area, pore habit, and tortuosity using in-situ imaging of Xenon (Xe) hydrate formation and dissociation in porous media with dynamic three-dimensional synchrotron microcomputed tomography (SMT). Xe hydrate was formed inside a high- pressure, low-temperature cell and then dissociated by thermal stimulation. During formation and dissociation, full 3D SMT scans were acquired continuously and reconstructed into 3D volume images. Each scan took only 45 seconds to complete, and a total of 60 scans were acquired. Hydrate volume and surface area evolution were directly measured from the SMT scans. At low hydrate saturation, the predominant pore habit was surface coating, while the predominant pore habit at high hydrate saturation was pore filling. A second-degree polynomial can be used to predict variation of tortuosity with hydrate saturation with an R2 value of 0.997. The Authors, published by EDP Sciences, 2020. This publication was made possible by partial funding from NPRP grant # NPRP8-594-2-244 from the Qatar national research fund (a member of Qatar Foundation) and the Institute for a Secure and Sustainable Environment (ISSE), University of Tennessee-Knoxville, USA. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of funding agencies. The authors would like to thank Mr. Wadi Imseeh for his help during scanning and Mr. Jamal Hannun for his help in interfacial area analysis. This paper used resources of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory (ANL) under Contract No. DE-AC02-06CH11357. The PSMT images presented in this paper were collected using the x-ray Operations and Research Beamline Station 13-BMD at Argonne Photon Source (APS), ANL. We thank Dr. Mark Rivers of APS for help in performing the PSMT scans. We also acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is supported by the National Science Foundation, Earth Sciences (EAR-1128799), and the DOE, Geosciences (DEFG02-94ER14466). Scopus

Cylindrical graphite microbial fuel cell (MFC) configuration designed by eliminating distinct casing and membrane was evaluated for bioelectrogenesis and treatment of real-field wastewaters. Both petroleum refinery wastewater (PRW) and Labanah whey wastewater (LW) were used as substrates, and investigated for electricity generation and organic removal under batch mode operation. PRW showed higher bioelectricity generation (current and power generation of 3.35 mA and 1.12 mW at 100 ) compared to LW (3.2 mA and 1.02 mW). On the contrary, higher substrate degradation efficiency was achieved using LW (72.76%) compared to PRW (45.06%). Superior function of MFC operation in terms of volumetric power density (PRW, 28.27 W/m3; LW, 23.23 W/m3) suggesting the feasibility of using these wastewaters for bioelectricity generation. Large sources of wastewater that generating in the Middle-East countries have potential to produce renewable energy from the treatment, which helps for the sustainable wastewater management and simultaneous renewable energy production. This publication was made possible by NPRP grant # 6-289-2-125 from the Qatar National Research Fund (a member of Qatar Foundation). Scopus

Methane hydrate is considered a potential energy source, with worldwide reserves on the order of 500–10,000 Gt of carbon. The production of Methane from hydratebearing sediments requires hydrate dissociation for releasing mobile methane gas in sediments prior to gas production operation. Existence of even a small fraction of fines can greatly decrease the permeability of sandy sediments, which will affect the gas recovery process. Fines can migrate through or clog the pores of sandy sediments depending on geometric constraints such as the ratio of the size of the pore throat to the size of the fine particle. In multiphase flow, clogging of fines at the pores causes a change in pressure gradient which affects the flow of gas through the pores and might induce gas driven fracture. In the literature, there is a major knowledge gap that needs to be resolved to develop technical and economically viable methane production strategies from gas hydrate reservoirs. A comprehensive understanding of the underlying physical processes such as fines migration, clogging, and gas-driven fracture during gas production in hydrate bearing sediments is needed. Effects of fines migration and clogging on gas flow path and gas driven fracture were studied for Carbon Dioxide (CO2). This was achieved by conducting multiphase flow experiments on brine saturated sand-kaolinite mixtures using 2D Hele-Shaw cell; a common analogous model that has been used to investigate particle displacement process in sediments and has the unique advantage in allowing real-time visualization. The cell consists of two transparent acrylic sheets that are separated by a small gap. The gap between the two sheets is maintained using filter sheets that have a thickness of 1/16 in. (1.6 mm) at the boundaries. Fluids flow radially between the sheets through a port in the middle of the bottom sheet. Multiphase flow experiments are conducted on samples of brine saturated uniform F75 sand mixed with kaolinite at different percentages by weight (0% to 20%). Pressure volume actuator (flow pump) is used to inject brine into the sample for saturation. Following saturation, CO2 is applied to the cell at a constant pressure (2 kPa, 5 kPa, and 10 kPa). Variation of gas pressure is monitored using a pressure sensor that is attached near the port of the cell. The injection processes are recorder using a high resolution digital camera mounted above the cell. Gas pressure was found to increase with increasing fines content, which indicates the clogging of pores by kaolinite particles. Particle image velocimetry (PIV) analysis was conducted using PIVLAB code on MatLab. Velocity vector field and density plots of velocity field were generated to track particles displacements. Particles near the fracture tip were moving at the highest velocity. The results showed three different regimes of gas flow through sediments. For low concentration of fines, the gas percolates through the pores with no major host particles displacement. For a high concentration of fines, major particle displacement occurs and gas driven fractures are created. Gas solely flows through those generated cracks with no observed percolation. Finally, a combination of the two regimes takes place for intermediate fines content.

Hybrid based bioelectrochemical system (BES) configured with embedded anode and cathode electrodes in soil was tested for the bioelectrochemical degradation of petroleum refinery wastewater (PRW). Four applied potentials were studied to optimize under batch mode operation, among which 2 V resulted in higher COD degradation (69.2%) and power density (725 mW/m2) during 7 days of operation. Further studies with continuous mode of operation at optimized potential (2 V) showed that hydraulic retention time (HRT) of 19 h achieved the highest COD removal (37%) and highest power density (561 mW/m2). BES function with respect to treatment efficiencies of other pollutants of PRW was also identified with respect to oil and grease (batch mode, 91%; continuous mode, 34%), total dissolved salts (batch mode, 53%; continuous mode, 24%) and sulfates (batch mode, 59%; continuous mode, 42%). Soil microenvironment in association with BES forms complex processes, providing suitable conditions for efficient treatment of PRW. ? 2018 Elsevier Ltd This publication was made possible by NPRP grant # 8-594-2-244 from the Qatar National Research Fund , Qatar (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors. Scopus

Bioelectrochemical systems (BESs) were evaluated for the bioelectrochemical treatment (BET) of petroleum refinery wastewater (PRW) by applying mild electrochemical potential in the range of 400?1000 mV on a single chamber membrane-less BES configured with anodic and cathodic biofilms. After four days of cycle operation in batch mode, BES achieved a maximum current density of 278 mA/m2 and a power density of 222 mW/m2 using applied potential of 800 mV. This system also achieved COD degradation rate of 0.364 kg COD/m3-day. Diesel range organics (DROs) exhibited more than 90% degradation, which is 15 times higher than the abiotic control. Electrochemically active bioanode and biocathode contributed to the degradation of PRW through both oxidation and reduction reactions with mild applied potentials. This also resulted in a 30% improvement in COD removal compared to MFC with biocatalyst only on the anode. The function of improved bioelectrochemical treatment was also exhibited by redox current values of cyclic voltammograms. ? 2018 Elsevier Ltd This publication was made possible by NPRP grant # 6-289-2-125 from the Qatar national research fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. The Authors would like to acknowledge the Environmental Science Centre (ESC) , Qatar University for the support in evaluating the samples for diesel range organics (DROs). Scopus

A common source of contamination of soil and groundwater in arid and (semi)-arid coastal regions are accidental spills of petroleum products, such as crude oil, gasoline, and diesel fuel. Groundwater pollution by petroleum hydrocarbons is a serious pollution problem that poses hazards to water resources and living organisms including humans. After release to the sub surface, hydrocarbons move downward through the aerobic vadose zone under the force of gravity. Eventually, they reach the groundwater table, where oil overlay promotes the development of anaerobic conditions. The oil phase that occurs as floating product on the water table and as residuum on soil grains provides a continued source supplying hydrocarbons to the groundwater. Accumulations of residual hydrocarbons at or near the water table may undergo smearing due to variations in water table elevation driven by, for example, seasonal changes in recharge and discharge or by tidal forcing in coastal environments. In subsurface environments contaminated by petroleum products, the geochemical conditions near the water table, in particular, the oxygen availability, moisture content, salinity, pH, nutrient concentrations and temperature, are important determinants of biogeochemical processes. Among these variables, the interplay of moisture content, oxygen availability and temperature are critical for understanding the biodegradation of petroleum hydrocarbons in arid and (semi)-arid coastal soil environments. In addition, the fate and transport of hydrocarbons in groundwater also depend on the redox conditions, soil mineralogy and microbial community structure, as well as the availability of suitable electron acceptors and nutrients. We hypothesize that the transition zone between the vadose zone and the groundwater system represents a hot spot for the degradation of petroleum hydrocarbons. This transition zone, however, is a dynamic biogeochemical environment, whose functioning is closely linked to the amplitude and frequency of water table fluctuations. We propose to determine the role of water table fluctuations on the coupled hydrological and biogeochemical processes that affect the degradation and partitioning of petroleum hydrocarbons, under conditions relevant to aquifers. Coastal areas in this regard can function as zones of contaminant mass transfers between aquifers and surface water bodies, but also as excellent spots of in situ bioremediation of contaminated soil and groundwater thanks to coupled hydrological and biogeochemical processes. The main objectives of this project are to: 1) quantify the level of sorption and biodegradation of multi-component hydrocarbons in soil and groundwater; 2) quantify the rates of hydrocarbon biodegradation under oscillating aerobic and sulfate reducing conditions in groundwater contaminated with petroleum hydrocarbons; 3) determine the oxygen dynamics in the vadose zone and groundwater affected by hydrocarbon dispersion under variable water table fluctuation regimes; 4) assess the rates and mechanisms of biogeochemical reactions regulating groundwater nutrient turnover during hydrocarbon spill and its movement under conditions of groundwater table fluctuations; and 5) develop a reactive transport model for groundwater pollution by petroleum hydrocarbons. In this project, we combine the acquisition of integrated physical, chemical and microbial data using uniquely designed process-oriented experimental approaches. The results of this project will significantly add to the quantitative knowledge on the effects of water table fluctuations on the release and degradation of petroleum-derived hydrocarbon contaminants in soil environments that experience both arid conditions and tidally-driven water table fluctuations. The expected results of the research will inform groundwater management and protection in arid and (semi)-arid coastal environments. To quantify the level of sorption and biodegradation of petroleum hydrocarbons in subsurface soils and groundwater (Objective 1), we conducted a series of controlled-laboratory batch experiments under variable salinity, temperature and water chemistry conditions. The soil samples were collected from the eastern coast of Qatar which is close to the North Gas and Al-Shaheen Oil Fields. The initial physical characterization of soil samples showed sand classification with the texture class of sabkhas soil. The results of soil-phase chemical characterization suggested that the dominant minerals of the soil are calcite, dolomite and gypsum and the concentrations of chloride and sodium were found to be high with a chloride-to-sodium ratio of ∼1.6.We used volatile benzene and naphthalene hydrocarbons to determine the sorption and biodegradation rates. The results of sorption experiments showed that naphthalene was adsorbed to the soil more than benzene where the initial aqueous concentrations of benzene and naphthalene were reduced at equilibrium due to sorption by approximately 10% and 75%, respectively. This difference was attributed to the organic carbon-water partitioning coefficient which is higher for naphthalene. We developed a sorption kinetics model to define the sorption isotherm of benzene and naphthalene hydrocarbons for the specific coastal soil collected from Qatar site. The model assumes the two sites sorption to the soil, one site in local equilibrium and the other site on first-order kinetic sorption, and the best fits were found for the Langmuir sorption isotherm type for the used hydrocarbons and soil in this project. In this presentation, we present the results of sorption and biodegradation batch experiments as well as the design of a unique dynamic soil column experiment to understand the dynamic responses of the fate, transport and degradation of hydrocarbons and the soil biogeochemical processes to the relatively abrupt changes in hydrogeochemical and climatic conditions.

The structure of natural hydrate-bearing sediments that exist offshore or onshore is a combination of coarse-grained sediments and fine-grained particles. During gas production from hydrate-bearing sediments, fine particles may migrate with the flowing fluids within pore space and cause clogging of the pore space of the porous media. Therefore, fine particles play a significant role during methane production from hydrate-bearing sediments as it impact the overall sediment formation performance and production efficiency. The migration of fine particles and its impact on clogging have been investigated in a single-phase flow, but it has not been clearly understood in a multi-phase flow. This research focuses on the study of fines migration and clogging behavior during single and multi-phase flow which can be implicated in gas production from hydrates bearing sediments. Microfluidic pore models that mimic porous media with different pore throat sizes were fabricated and utilized to study fines migration and clogging behavior in porous media. Artificial particles and natural fine particles were selected to represent fine particles. The impact of flow rate, pore-fluid types, particle concentration, and pore-throat to fine particle size ratio was investigated. Fine particles used in this research include polystyrene latex particles, silica, and kaolinite. Pore-fluids used in this study include deionized (DI) water, and sodium chloride (NaCl) brine (2M concentration). The particle concentrations covered from 0.1% to 10%. And the pore-throat widths were fabricated from 40 μm to 100 μm. Single-phase flow experiments were conducted to show that the concentration of fine particles required to form clogging in pores increased as flow rate decreased. The results obtained using polystyrene latex particles provide the insight at a relatively higher flow rate (50 μl/min) than literature studies that fine particles with 2% concentration can migrate in the pore throat without bridge or clogging at the various pore throat and fine particle size ratios (o/d = 2.6∼36.4). Furthermore, silica presents higher critical clogging concentration (0.5% in brine) compared with kaolinite (0.2% in brine) when the pore-throat width equal to 60 μm due to the larger pore throat and fine particle size ratio. On the other hand, the findings show that clogging easily occurred at a lower pore-throat to fine particle size ratio even with a few number of fine particles. In addition, pore-fluid type directly influences the tendency of fine's to form clusters which in turn impacts the clogging behavior. For instance, silica fines clogging easier occurs in brine solution compare within deionized water due to larger cluster size in brine, while kaolinite shows an opposite result which means the kaolinite has higher clogging possibility in deionized water compared within brine solution. On the other hand, findings of multi-phase flow experiments show that fine particles accumulate along the liquid-gas interface and migrate together, which in turn cause bridging or clogging to occur easily in pores. These observations imply that a multi-phase flow during gas production could easily form clogging in pores, in which the flow permeability of porous media decreases even though clogging has not occurred in the same conditions with a single-phase flow. Thus, the permeability of porous media in engineering applications should be estimated by considering relatively easy clogging in pores in a multiphase flow compared to a single-phase flow. Findings of this research show the vital impact of pore-fluids and fluid-fluid interphase on fine particles migration and clogging in porous media. It provides a better understanding of the fines migration and clogging mechanisms. In addition, the results indicate the need to understand the types of fines and fluids in reservoir before evaluating if there will be a clogging potential during gas production from hydrates bearing sediments.

Electrochemically active anodic biofilm that has adapted under mild applied potentials in the range 100-500 mV was evaluated for its improved bioelectrogenesis and bioelectrochemical treatment of petroleum refinery wastewater (PRW) in a single chamber air cathode microbial fuel cell (MFC). MFC operation with 500 mV as supplemental voltage has exhibited a maximum power density of 132 mW/m2, which was three times higher than control MFC (45 mW/m2). Similarly, highest substrate removal efficiency (48%) was also obtained with the MFC of 500 mV, followed by 300 mV (37%), 100 mV (32%) and control (27%). Adaptation under applied potential conditions also exhibited enhanced degradation efficiency of diesel range organics (DROs)/straight chain-alkanes. The strategy efficiently reduced DROs with the maximum efficiency of 89% (500 mV), which is almost 50% higher than that of the control system (59%), demonstrating the effectiveness of using supplemented voltage in treating PRW. 2018 Elsevier Ltd This publication was made possible by NPRP grant # 6-289-2-125 from the Qatar national research fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. The Authors would like to acknowledge the Environmental Science Centre (ESC), Qatar University for evaluating the samples for diesel range organics (DROs). Scopus

Considerable activities from the oil and natural gas sector have risen some concerns about the pollution of soil and groundwater by petroleum hydrocarbons (PHCs) in (semi)-arid coastal regions. The understanding of the fate and transport of PHCs in these regions is therefore necessary to develop strategies for remediation. To quantify the sorption rates of PHCs in (semi)-arid coastal soil environments, we conducted a series of controlled-laboratory batch experiments under variable temperature and salinity conditions. The soil samples were collected from the eastern coast of Qatar which is near the two largest off-shore oil and natural gas fields of the country (North Gas and Al-Shaheen Oil Fields), and the volatile benzene and naphthalene were used as PHCs. The characterization of soil samples showed sand classification with the texture class of sabkha and saline beach sandy soils with calcite as potential dominant mineral. The concentrations of dissolved chloride and sodium were found to be high (> 400 mg L?1) with a chloride-to?sodium ratio of about 1.7. The results of sorption experiments showed that the rates of naphthalene sorption were more than for benzene, where the initial aqueous concentrations of benzene and naphthalene were reduced at equilibrium due to sorption by about 14�25% and 65�79%, respectively. This difference was attributed mainly to the organic carbon-water partitioning coefficient which is higher for naphthalene. The sorption rate experiments showed that sorption was stronger for benzene under higher salinity and lower temperature conditions. The sorption of naphthalene was not affected by the change in salinity but increased by 18% when the temperature decreased from 35 to 5 �C. A sorption kinetic model was also applied to define the sorption behavior of benzene and naphthalene for the coastal soil collected in Qatar and the best fits were achieved with the Langmuir sorption isotherm. ThispublicationwasmadepossiblebyNPRPgrant#NPRP9-93-1-021fromtheQatarnationalresearchfund(amemberofQatarFoundation).Thefindingsachievedhereinaresolelytheresponsibilityoftheauthors.WealsowouldliketoacknowledgethefundingprovidedbytheCanadaExcellenceResearchChairprograminEcohydrology.WearethankfultoMarianneVandergriendt,SierraWillowCranmer-Smith,andHeatherTownsendfortheirvaluableassistanceduringtheexperimentsandanalyses,andShirleyChattenforgaschromatographyanalysis.WealsothankReemIsmailforcollectingthesoilsamplesfromthefieldsiteinQatar.AppendixA Scopus

The constitutive behavior of sheared sand is highly influenced by particle morphology, gradation, mineralogy, specimen density, loading condition, stress path, and boundary conditions. The current literature lacks a three-dimensional (3D) systematic experimental study that investigates the influence of particle morphology, confining pressure, and specimen density on the failure mode of sheared sand. In this paper, surface texture, roundness, and sphericity of three uniform sands and glass beads with similar grain size were quantified by using 3D images of particles. In situ nondestructive 3D synchrotron microcomputed tomography (SMT) was used to monitor the deformation of medium-dense and very dense dry sand specimens that were tested under axisymmetric triaxial loading condition at 15 and 400 kPa confining pressures. The particles were identified and tracked in 3D as shearing progressed within the specimens, and maps of incremental particle translation and rotation were developed and used to uncover the relationship between particle morphology, specimen density, and confining pressure on the deformation and failure mode of sheared sand. This paper discusses the relationship between the failure mode and particle morphology, specimen density, and confining pressure. Scopus

The concept of representative elementary volume (REV) is critical to understand and predict the behavior of effective properties of complex heterogeneous materials in a multiscale manner. Porosity is usually used to define the REV of a given material, if porosity is stationary over consecutive volumetric increments, the sample is considered as REV regardless of the behavior of other microstructure properties. To investigate this common assumption, the change of key microstructure parameters such as local void ratio, sphericity, angularity, and coordination number of particles was computed over different volumes of REV for porosity. X-ray computed tomography was used to obtain three-dimensional volumes of natural sand packed at four different particle fragments. Efficient and robust algorithms were used to compute the microstructure properties from three-dimensional images. Findings revealed that the REVmin for porosity may not be adequate to be considered as a REV for parameters such as particle size dist...

The concept of representative elementary volume (REV) is critical to understand and predict the behaviour of effective parameters of complex heterogeneous media (e.g., soils) in a multiscale manner. Porosity is commonly used to define the REV of a given sample. In this paper we investigated whether the use of a REV for porosity can be used as a REV for other parameters such as particle size distribution, local void ratio and coordination number. X-ray computed tomography was used to obtain 3D images (i.e., volumes) of natural sand systems with different particle size distributions. 3D volumes of four different systems were obtained and a REV analysis was performed for these parameters utilizing robust 3D algorithms.Findings revealed that the REVmin for porosity may not be adequate to be considered as a REV for parameters such as particle size distribution, local void ratio and coordination number. The REVmin for these parameters was observed to be larger than the REVmin for porosity. Heterogeneity of the systems was found to be an important factor to determine the REV for the parameters analyzed in this paper. The REV analysis revealed that as the uniformity coefficient increased, a larger volume was required to obtain the REVmin for the distribution of particle sizes and coordination number whereas a smaller volume was required to obtain the REVmin for local void ratio. Therefore, determination of the REV for parameters described in this paper or any microscale parameter of concern should not be derived based on REV for porosity and should be determined based on their distributions over different volumes. © 2010 Elsevier B.V.

The objective of this paper was to investigate the impact of wettability of porous media on pore-scale characteristics of residual nonaqueous phase liquids (NAPLs). Synchrotron X-ray microtomography was used to obtain high-resolution three-dimensional images of fractionally wet sand systems with mean grain size of 250 microm. Pore-scale characteristics of NAPL blobs such as volume, lengths, interfacial areas, and sphericity index were computed using three-dimensional image processing algorithms. Four systems comprised of 100, 50, 25, and 0% NAPL-wet mass fractions containing the residual NAPL were imaged and analyzed. Findings indicate that spatial variation in wettability of porous media surfaces has a significant impact on pore-scale characteristics of residual NAPL blobs in saturated porous media systems. As the porous media comprises more water-wet surfaces, residual NAPL blobs increase in size and length due to the entrapment at large pore bodies. NAPL-water interfacial areas tend to increase as the NAPL-wet surface fractions increase in the systems. Overall residual NAPL saturations are less in fractionally wet systems and increase as the systems become more NAPL-wet or water-wet.

An optimization based model that simulates random packings of polydisperse particles to mimic porous media systems is presented in this paper. The model simulates systems with properties that map back to physically measured quantities. The model is composed of three main procedures: detachment of an existing sphere from a target sphere by moving its center to a new position, movement of an existing sphere to touch the target sphere, and addition of a new sphere to touch the target sphere. Each procedure is performed to satisfy a constrained nonlinear optimization formulation. Input parameters include radius and coordination numbers density functions. A monodisperse and polydisperse packings were simulated by incorporating physically based properties of glass bead packings obtained from 3D computed tomography images. In each simulated system, the packing density obtained was very close to the packing density of the physical system. The packings were tested for isotropy, homogeneity and randomness and then compared to experimental microtomography images. Findings indicate that the packings generated were isotropic, homogenous, random, and in a good agreement with the experimental data.

This paper presents techniques and algorithms to compute microstructure properties of irregular-shaped granulate assemblies utilizing 3D images. The techniques are capable of extracting microstructure properties of particles such as centeroid, particle size distribution, shape indices (i.e., sphericiy and angularity), number of contacts (i.e., distribution of coordination numbers), contact network, packing efficiency, distribution of local void ratio and radial distribution function. Such properties are critical parameters for micromechanical-based numerical models to capture micro- and macromechanical behavior of geomaterials. X-ray microtomography was used to reconstruct high-resolution 3D image of a natural sand system to represent granular materials. Microstructure properties of the sand system were computed and compared with properties of a computer-simulated image of periodic random spheres. Findings indicate that the use of simplified systems of idealized spheres to model micro- and macromechanical behavior of granular systems can lead to inaccurate results due to the differences in the microstructure between both systems. Methods presented in this paper enabled capturing a more realistic microstructure that can be incorporated in micromechanical models to better simulate, understand, or explain macroscale behavior of granular materials based on their actual microstructure.