Packed Glass Beads Research Articles

Pore Network Drying Model for Particle Aggregates: Assessment by X-Ray Microtomography

Convective drying of disordered glass bead packings has been investigated both experimentally and numerically. X-ray microtomography (XMT) and image analysis techniques have been used to determine the three-dimensional spatial distribution of the liquid and solid phases at the pore scale within the wet particle aggregates. The evolution of the liquid distribution in the aggregate has been tracked during the drying process. Particle center coordinates and radii have been extracted from the X-ray images using binarization and segmentation techniques. Based on this geometric data for a real aggregate, a pore network approximation of the pore space has been generated from a Voronoi tessellation about particle centers by designating Voronoi edges as interconnected cylindrical pores with radii computed from the distance between neighboring particles. This three-dimensional irregular pore network takes into account both the geometrical and topological characteristics (pore size distribution and connectivity) of the actual pore space. Drying simulations have been carried out for the pore networks obtained from the XMT and results are presented as phase distributions and moisture profiles. The simulated liquid phase distributions are in qualitative agreement with the experimental result, which indicates that pore network models are suited to describe the drying of dense particle aggregates at the pore scale.

Experimental and numerical study of compositional two-phase displacements in layered porous media

This paper presents an experimental and numerical study to investigate the effects of viscous, capillary, and gravity forces on compositional two-phase displacements in layered porous media. We use glass bead packs of different sizes to construct a quasi 2-D porous medium of three layers with different uniform permeabilities. We adapt an analog ternary fluid system (isooctane, brine, and isopropanol) which allows us to control interfacial tension between the phases at ambient laboratory conditions. Flooding experiments mimic condensing drives and use immiscible and near miscible fluids from the analog ternary system. We report recovery of phases, compositional analysis, and snapshots of saturation distributions during each experiment.We show that the high flow capacity domain as defined by the high permeability layer and its thickness always dominate displacements. However, its degree depends on the location of the high-permeability layer and the balance between the driving forces. Compositional analysis of effluent indicates that the compositional path is slightly different for the low and high injection rates in the high interfacial tension (IFT) immiscible displacements whereas it is sensitive to the location of high-permeability layer in the low-IFT near-miscible floods. The Peclet numbers indicate the presence of dispersion in the experiments and crossflow affects the recoveries.We also perform black oil simulations to interpret the experimental observations. In general, we obtain consistent results between the experimentally measured and numerically obtained data. However, in order to account for the displacement physics and accurately predict the recovery performance, one may need to employ a fully compositional simulation model that captures the tie-line slopes correctly along with the transport properties and gravity. The compositional simulations can provide additional details in terms of component recoveries.

Effect of Temperature on Athabasca Type Heavy Oil – Water Relative Permeability Curves in Glass Bead Packs

There have been a number of somehow contradictory reports in the literature on the effect of temperature on oil and water relative permeabilities. Although some authors have reported the dependence of relative permeability curves on temperature, others have attributed these dependencies to artifacts inherent in unsteady-state method of relative permeability measurement. In order to further investigate the impact of temperature changes on the relative permeability data, we have conducted laboratory core flooding experiments on heavy oil systems. The porous media used was glass bead packs, and the Athabasca type bitumen with varying viscosities was displaced by hot water. The history matching technique was conducted on production and pressure differential data to get the relative permeability curves. Results indicated that generally the increase in initial water saturation and the decrease in residual oil saturation are expected by increasing temperature. However, viscous instabilities can rule out the above mentioned trends. No temperature dependency of either oil or water relative permeability can be justified in our tests. The changes in relative permeabilities by temperature are probably related to experimental artifacts, viscous fingering and changes in oil to water viscosity ratio and not fundamental flow properties.

Drying in porous media with gravity-stabilized fronts: Experimental results

In a recent paper [Yiotis et al., Phys. Rev. E 85, 046308 (2012)] we developed a model for the drying of porous media in the presence of gravity. It incorporated effects of corner film flow, internal and external mass transfer, and the effect of gravity. Analytical results were derived when gravity opposes drying and hence leads to a stable percolation drying front. In this paper, we test the theory using laboratory experiments. A series of isothermal drying experiments in glass bead packings saturated with volatile hydrocarbons is conducted. The transparent glass cells containing the packing allow for the visual monitoring of the phase distribution patterns below the surface, including the formation of liquid films, as the gaseous phase invades the pore space, and for the control of the thickness of the diffusive mass boundary layer over the packing. The experimental results agree very well with theory, provided that the latter is generalized to account for the effects of corner roundness in the film region (which was neglected in the theoretical part). We demonstrate the existence of an early constant rate period (CRP), which lasts as long as the films saturate the surface of the packing, and of a subsequent falling rate period (FRP), which begins practically after the detachment of the film tips from the external surface. During the CRP, the process is controlled by diffusion within the stagnant gaseous phase in the upper part of the cells, yielding a Stefan tube problem solution. During the FRP, the process is controlled by diffusion within the packing, with a drying rate inversely proportional to the observed position of the film tips in the cell. Theoretical and experimental results compare favorably for a specific value of the roundness of the films, which is found to be constant and equal to 0.2 for various conditions, and verify the theoretical dependence on the capillary Ca(f), Bond Bo, and Sherwood Sh numbers.

Exchange relaxometry of flow at small Péclet numbers in a glass bead pack

In this paper we consider low Péclet number flow in bead packs. A series of relaxation exchange experiments has been conducted and evaluated by ILT analysis. In the resulting correlation maps, we observed a collapse of the signal and a translation towards smaller relaxation times with increasing flow rates, as well as a signal tilt with respect to the diagonal. In the discussion of the phenomena we present a mathematical theory for relaxation exchange experiments that considers both diffusive and advective transport. We perform simulations based on this theory and discuss them with respect to the conducted experiments.

Numerical simulation of solidification of liquid copper saturated in porous structures fabricated by sintered steel particles

PurposeThe purpose of this paper is to solve solidification of liquid copper saturated in porous structure fabricated by sintered steel particles using a temperature‐transforming model (TTM).Design/methodology/approachThe convection in the liquid region is modeled using Navier‐Stokes equation with Darcy's term and Forchheimer's extension. The effect of natural convection is considered using the Boussinesq approximation. For the solid region, the velocity is set to zero by the Ramped Switch‐Off Method (RSOM). The model was validated by comparing the results with existing experimental and numerical results with gallium as phase change material and packed glass beads as porous structure. Solidification of liquid copper saturated in sintered copper particles is then simulated and the effects of various parameters on solidification process were studied.FindingsThe results indicate that the stronger convection effects are shown for the cases with high Raleigh number or high Darcy's number. However, when either Raleigh number or Darcy's number is reduced to below a certain order of magnitude, the solidification becomes conduction‐controlled.Originality/valueThis work is the first application of the TTM to solve solidification in porous media, which can find its application in post‐processing of laser sintered parts.

Frequency-Dependent Streaming Potential of Porous Media—Part 2: Experimental Measurement of Unconsolidated Materials

Frequency-dependent streaming potential coefficient measurements have been made upon Ottawa sand and glass bead packs using a new apparatus that is based on an electromagnetic drive. The apparatus operates in the range 1 Hz to 1 kHz with samples of 25.4 mm diameter up to 150 mm long. The results have been analysed using theoretical models that are either (i) based upon vibrational mechanics, (ii) treat the geological material as a bundle of capillary tubes, or (iii) treat the material as a porous medium. The best fit was provided by the Pride model and its simplification, which is satisfying as this model was conceived for porous media rather than capillary tube bundles. Values for the transition frequency were derived from each of the models for each sample and were found to be in good agreement with those expected from the independently measured effective pore radius of each material. The fit to the Pride model for all four samples was also found to be consistent with the independently measured steady-state permeability, while the value of the streaming potential coefficient in the low-frequency limit was found to be in good agreement with other steady-state streaming potential coefficient data.

The influence of hydraulic loads on depth filtration

The influence of hydraulic loads on the detachment of particles from the collector surface or from previously retained particles was observed in a packed glass beads column. A hydraulic shock load (i.e., 20% increase of flow rate) was applied after 4 h of particle attachment at a constant flow rate. A single type of particle suspension (Min-U-Sil 5, nearly pure SiO 2) and three different chemical conditions (pH control, alum and polymer destabilization) were utilized. The magnitude of particle detachment increased with increasing particle size for non-Brownian particles because more shear force was applied to large particles due to their large surface area. More favorable particles (i.e., particles with small surface charge) were detached to a lesser extent than unfavorable particles during the hydraulic shock loads application. This phenomenon can be caused by floc strength. In some cases, when the zeta potential of influent particles was relatively high, the magnitude of detachment of bigger particles (e.g., 4.0–5.0 μm) was less than that of smaller particles (e.g., 3.0–4.0 μm). This can be attributable to the breakup of detached flocs as an individual particle. It was also found that the shape of the curve relating the magnitude of particle detachment and particle size can be concave, linear, or convex depending on physicochemical conditions such as floc strength.

Contact line extraction and length measurements in model sediments and sedimentary rocks

The mechanisms that govern the transport of colloids in the unsaturated zone of soils are still poorly understood, because of the complexity of processes that occur at pore scale. These mechanisms are of specific interest in quantifying water quality with respect to pathogen transport (e.g. Escherichia coli, Cryptosporidium) between the source (e.g. farms) and human users. Besides straining in pore throats and constrictions of smaller or equivalent size, the colloids can be retained at the interfaces between air, water, and grains. Theories competing to explain this mechanism claim that retention can be caused by adhesion at the air–water-interface (AWI) between sediment grains or by straining at the air–water–solid (AWS) contact line. Currently, there are no established methods for the estimation of pathogen retention in unsaturated media because of the intricate influence of AWI and AWS on transport and retention. What is known is that the geometric configuration and connectivity of the aqueous phase is an important factor in unsaturated transport. In this work we develop a computational method based on level set functions to identify and quantify the AWS contact line (in general the non-wetting–wetting–solid contact line) in any porous material. This is the first comprehensive report on contact line measurement for fluid configurations from both level-set method based fluid displacement simulation and imaged experiments. The method is applicable to any type of porous system, as long as the detailed pore scale geometry is available. We calculated the contact line length in model sediments (packs of spheres) as well as in real porous media, whose geometry is taken from high-resolution images of glass bead packs and sedimentary rocks. We observed a strong dependence of contact line length on the geometry of the sediment grains and the arrangement of the air and water phases. These measurements can help determine the relative contribution of the AWS line to pathogen retention.

Microtomography of Imbibition Phenomena and Trapping Mechanism

Water imbibition during the waterflooding process of oil production only sweeps part of the oil present. After water disrupts the oil continuity, most oil blobs are trapped in porous rock by capillary forces. Developing an efficient waterflooding scheme is a difficult task; therefore, an understanding of the oil trapping mechanism in porous rock is necessary from a microscopic viewpoint. The development of microfocused X-ray CT scanner technology enables the three-dimensional visualization of multiphase phenomena in a pore-scale. We scanned packed glass beads filled with a nonwetting phase (NWP) and injected wetting phase (WP) in upward and downward injections to determine the microscopic mechanism of immiscible displacement in porous media and the effects of buoyancy forces. We observed the imbibition phenomena for small capillary numbers to understand the spontaneous imbibition mechanism in oil recovery. This study is one of the first attempts to use a microfocused X-ray CT scanner for observing the imbibition and trapping mechanisms. The trapping mechanism in spontaneous imbibition is determined by the pore configuration causing imbibition speed differences in each channel; these differences can disrupt the oil continuity. Gravity plays an important role in spontaneous imbibition. In upward injection, the WP flows evenly and oil is trapped in single or small clusters of pores. In downward injection, the fingering phenomena determine the amount of trapped oil, which is usually in a network scale. Water breakthrough causes dramatic decrease in the oil extraction rate, resulting in lower oil production efficiency.

The Effect of Reservoir Wettability on the Production Characteristics of the VAPEX Process: An Experimental Study

The impact of fractional wettability on the production characteristics of a VAPEX process at the macroscale was investigated. Conventional VAPEX experiments were conducted in a 220 Darcy random packing of glass beads in a rectangular physical model and n-pentane was used to recover the Cold Lake bitumen from the oil-saturated model in the absence of connate water. The composition of oil-wet beads in the packed bed was altered from completely water-wet beads to completely oil-wet beads at different proportions of oil-wet beads mixed with water-wet beads. A substantial increase (about 40%) in the production rate of live oil was observed during the VAPEX process when the wettability of the porous packing was entirely oil-wet beads. A critical oil-wet fraction of 0.66 was found for the heterogeneous packing of water-wet and oil-wet beads of similar size distribution. Above this critical composition, the live oil production rate was not affected by further increase in the proportion of the oil-wet beads. It is believed that above this critical composition of the oil-wet beads, the crevice flow process is dominated by the continuity of higher conductivity live oil films between particles through the oil-wet regions. Below this critical composition, the live oil production rate increased linearly with the fraction of the oil-wet beads in the packing. The oil-wet regions favor the live oil drainage compared to that of the water-wet regions as they enhance the rate of imbibition of the live oil from the oil-filled pores to the vacated pores near the nominal VAPEX interface. These two factors enhance the live oil production rate during the VAPEX process. The solvent content of the live oil, the solvent-to-oil ratio (SOR), and the residual oil saturation did not correlate strongly with the proportion of the oil-wet beads in the packing. The average solvent content of the live oil and the residual oil saturation were measured to be 48% by weight and 7% by volume respectively.

Elastic weakening of a dense granular pack by acoustic fluidization: Slipping, compaction, and aging

Sound velocity measurements in dense glass bead packs reveal significant softening effect at large amplitudes, due to the frictional nonlinearity at the grain contacts. Beyond a certain amplitude, the sound-matter interaction becomes irreversible, leaving the medium in a weakened and slightly compacted state. A slow recovery of the initial elastic modulus is observed after acoustic perturbation, revealing the plastic creep growth of microcontacts. The cross-correlation function of configuration-specific acoustic speckles highlights the relationship between the macroscopic elastic weakening and the local change of the contact networks, induced by strong sound vibration, in the absence of appreciable grain motion.

Heavy oil and bitumen recovery by hot solvent injection

Thermal and miscible methods are commonly used for in situ recovery of heavy oil and bitumen. Both techniques have their own limitations and benefits. However, these methods can be combined by co-injecting solvent with steam or injecting solvent into a pre-heated reservoir. The current work was undertaken to study the performance of solvents at higher temperatures for heavy oil/bitumen recovery. Glass bead packs and Berea sandstone cores were used in the experiments to represent different types of pore structures, porosity and permeability. After saturating with heavy oil, the samples were exposed to the vapor of paraffinic solvents (propane and butane) at a temperature above the boiling point of the solvent, and a constant pressure of 1500 kPa. A mechanical convection oven was used to maintain constant temperature across the setup. The setup was designed in such a way that a reasonably long sample (up to 30 cm) can be tested to analyze the gravity effect. The oil recovered from each of these experiments was collected using a specifically designed collection system and analyzed for composition, viscosity and asphaltene content. The final amount of oil recovered in each case (recovery factor but not extraction rate) was also analyzed and the quantity and nature of asphaltene precipitated with each of the tested solvents under the prevailing temperature and pressure of the experiment was reported. Optimal conditions for each solvent type were identified for the highest ultimate recovery. It was observed that recovery decreased with increasing temperature and pressure of the system for both solvents, and that the best results were found when experimental temperature is only slightly higher than the saturation temperature of the solvent used. It was also noticed that butane diluted the oil more than propane which resulted in lower asphaltene content and viscosity of oil produced with butane as a solvent.

MRI study on CO2 flooding characteristics in n-decane saturated glass bead packs

CO2 enhanced oil recovery (EOR) offers the potential for both increasing domestic oil production and storing significant volumes of carbon dioxide emissions. Laboratory scale experiments are effective methods for the visualization and quantification of flooding characters. In this paper a series of experiments on n-decane displacement by both gaseous and supercritical CO2 flooding in glass bead pack were carried out using a 400 MHz magnetic resonance imaging (MRI) system. Images were obtained for direct visualization of the displacement procedures as CO2 was injected and processed to quantify the displacement parameters using image intensity analysis. Channeling and viscous fingering phenomena appeared obviously in the case of gaseous CO2 flooding. But there was no such two phase flow behavior in supercritical CO2 flooding because of the miscibility of supercritical CO2 with n-decane. Residual saturation of n-decane in glass bead packs was evaluated to be 32.2% for gaseous CO2 flooding and 14.5% for supercritical CO2 flooding. It was proved that miscible phase displacement can improve the efficiency of CO2 flooding notably.

An experimental investigation of the balance between capillary, viscous, and gravitational forces during CO2 injection into saline aquifers

Abstract Understanding of the processes which take place within a reservoir during and after CO2 injection is essential for successful selection of a storage site for carbon capture and storage. Flow regimes that occur when CO2 is injected into a geological formation control how much CO2 can be effectively injected and stored in the formation. This paper presents an experimental investigation of the scaling laws which describe CO2 injection into saline aquifers. Quasi two-dimensional experiments were performed in initially water-filled glass-bead packs to demonstrate the influence of gravitational, viscous and capillary effects on the vertical flow of CO2. The properties of fluids used in the experiments are analogous to the properties of CO2 and brine at possible reservoir conditions. Experiments are performed for a range of dimensionless capillary and CGR numbers which may describe conditions at existing storage sites. The use of dimensionless numbers links the laboratory experiments with the field scale observations and hence these numbers can be applied for the screening of potential storage sites. The experiments represent gravity and viscous unstable floods with fractal-like fronts. The gravity effects were more pronounced in cases with a low injection rate and high permeability, causing less brine displacement. Higher injection rates caused more fingering and increased total displacement.

Streaming potential coupling coefficient of quartz glass bead packs: Dependence on grain diameter, pore size, and pore throat radius

The Helmholtz-Smoluchowski (HS) equation is commonly used to relate the streaming potential coupling coefficient of rocks to their zeta potential, pore fluid dielectric permittivity, conductivity, and viscosity despite it being known for almost [Formula: see text] that it does not work well for porous media. One of the problems is that the HS equation contains no implicit dependence on grain size, pore size, or pore throat size. Another has been the lack of high-quality data relating the streaming potential coupling coefficient to rock microstructural parameters. In this, predominantly experimental work, we have measured the streaming potential coupling coefficient for 12 sizes of quartz glass beads and two fluid salinities. A comparison of the new data and the existing data with the conventional HS equation and Revil’s grain size-dependent HS model shows the grain size-dependent model to be far superior in describing the data. Recognizing their utility in reservoir characterization, we have developed new equations that describe how the streaming potential coupling coefficient varies with pore diameter and pore throat diameter. We have compared experimental determinations as a function of pore throat diameter with these new relationships and found them to work very well if the ratio of the mean pore diameter to the pore throat diameter is 1.662, which is valid for random arrangement of monodisperse spheres. The zeta potential has also been calculated from the grain size-dependent HS equations and are found to be approximately constant and in agreement with the theoretically predicted values. The equations presented in this paper allow the streaming potential coupling coefficient of a reservoir rock to be calculated as a function of grain size, pore size, and pore throat size.

Using NMR displacement measurements to probe CO2 entrapment in porous media

Carbon dioxide sequestration in aquifers is seen as a potential climate change mitigation technique. One physical mechanism by which this could occur is capillary trapping of discrete pore-scale CO2 bubbles (referred to as ganglia) in the pore space. Nuclear magnetic resonance (NMR) techniques were used to quantify the spatial distribution and pore environment of such CO2 entrapment in a model porous medium (random glass bead packing). 3D images revealed a relatively macroscopically homogeneous CO2 entrapment, even though the image resolution is insufficient to resolve individual CO2 ganglia. Quantification of the pore environment of the CO2 ganglia was achieved using NMR displacement propagators (displacement probability distributions), acquired both before and after CO2 entrapment. Lattice Boltzmann (LB) simulations were used to facilitate interpretation of the propagator statistics by considering various pore environments in which CO2 could become trapped. Comparison with the experimental data suggests that CO2 is preferentially entrapped in comparatively larger pores. © 2010 American Institute of Chemical Engineers AIChE J, 2011

Retention and release of TiO 2 nanoparticles in unsaturated porous media during dynamic saturation change

The retention and release of TiO 2 nanoparticles in porous media (packed glass beads) were studied under transient unsaturated conditions as the media were taken through multiple drainage/imbibition (drying/wetting) cycles at three different pH values. The focus of the work was to better understand the role of changing water table levels and rainfall infiltration events on the ultimate mobility of TiO 2 nanoparticles. Results indicate that retention during saturated transport varied considerably, from very strong retention at pH 5 (likely due to electrostatic interactions), to no measurable retention at pH 10. During primary drainage, additional retention (i.e., beyond what was retained during initial saturation) was observed at all pH values. During subsequent imbibition/drainage cycles where nanoparticle-free water was imbibed into the porous medium prior to drainage, the mass of retained TiO 2 remained nearly constant at all three pH values. Final imbibition/drainage and subsequent flushing, both using solution conditions adjusted to favor high mobility, showed very little additional nanoparticle release. These results indicate that the release of TiO 2 nanoparticles following retention by either saturated or unsaturated packed glass beads was difficult to achieve, regardless of the likely initial mechanisms of retention, even when solution conditions were changed to those that should favor high mobility.

Permeability mapping in porous media by magnetization prepared centric-scan SPRITE

The ability of porous media to transmit fluids is commonly referred to as permeability. The concept of permeability is central for hydrocarbon recovery from petroleum reservoirs and for studies of groundwater flow in aquifers. Spatially resolved measurements of permeability are of great significance for fluid dynamics studies. A convenient concept of local Darcy’s law is suggested for parallel flow systems. The product of porosity and mean velocity images in the plane across the average flow direction is directly proportional to permeability. Single Point Ramped Imaging with T 1 Enhancement (SPRITE) permits reliable quantification of local fluid content and flow in porous media. It is particularly advantageous for reservoir rocks characterized by fast magnetic relaxation of a saturating fluid. Velocity encoding using the Cotts pulsed field gradient scheme improves the accuracy of measured flow parameters. The method is illustrated through measurements of 2D permeability maps in a capillary bundle, glass bead packs and composite sandstone samples.

Dispersion and attenuation due to scattering from heterogeneities of the frame bulk modulus of a poroelastic medium

While Biot theory can successfully account for the dispersion observed in sand sediments, the attenuation at high frequencies has been observed to increase more rapidly than Biot theory would predict. In an effort to account for this additional loss, perturbation theory is applied to Biot's poroelastic equations to model the loss due to the scattering of energy from heterogeneities in the sediment. A general theory for propagation loss is developed and applied to a medium with a randomly varying frame bulk modulus. The theory predicts that these heterogeneities produce an overall softening of the medium as well as scattering of energy from the mean fast compressional wave into incoherent fast and slow compressional waves. This theory is applied to two poroelastic media: a weakly consolidated sand sediment and a consolidated sintered glass bead pack. The random variations in the frame modulus do not have significant effects on the propagation through the sand sediment but do play an important role in the propagation through the consolidated medium.