Role Of Colloidal Particles Research Articles

Investigating Pore-Throat Blockage in Tight Rocks: The Role of Colloidal Particles in Treated and Untreated Produced Water

Colloidal particles in produced water used for hydraulic fracturing can block pore throats in tight reservoir rocks through three main mechanisms. The blockage of these pore throats damages the permeability of the reservoir, leading to low productivity and higher operational cost. However, the characterization of these particles in produced water used for hydraulic fracturing is understudied. This study investigates the size distribution of these particles in produced water and the resulting pore plugging mechanisms potentially operating on typical 0.1, 0.2, and 0.4-micron-wide siltstone reservoir rock pore throats caused by primary, aggregate, and agglomerate particles in such produced waters. The siltstone pore throat diameters and particle diameters from untreated and treated produced water from McClean, McKenzie, Williams, and Mountrail Counties were compared and used to calculate the jamming ratios from which the main pore throat plugging mechanisms in those rocks were inferred. The results show that bridge blockage, and single pore blocking through straining are the main pore throat blocking mechanisms contributing to formation damage in these reservoir rocks. The bridge blocking mechanism is more prevalent when untreated produced water is used as the base fluid for hydraulic fracturing, while single pore blocking through straining is more prevalent in treated water. The size of the particles also affects the pore plugging mechanisms, with smaller particles causing damage through bridging and larger particles causing damage through single pore blockage and straining. These findings have important implications for the management of produced water in the oil and gas industry, as they may provide clues to minimize formation damage.

Colloidal Particle-Induced Microstructural Transition in Cellulose/Ionic Liquid/Water Mixtures.

The role of colloidal particles in enhancing the mechanical and thermal properties of liquid crystalline (LC) gels formed in microcrystalline cellulose/1-allyl-3-methylimidazolium chloride/water mixtures is experimentally investigated by means of rheology and polarized optical microscopy (POM). The overshoot in loss modulus and increase in the melting temperature of LC domains as observed in differential scanning calorimetry signal a stronger interaction of cellulose with both hydrophobic polystyrene and hydrophilic silica nanoparticles which in turn point to considerable amphiphilic nature of cellulose. The aggregation of nanoparticles observed by POM and the rheological behavior point to the development of a sample-spanning network of cellulose-nanoparticle clusters during the sol-gel transition with an increase in concentration of water. Furthermore, the LC gels obey Chambon-Winter (CW) criterion, indicating a self-similar gel network, except at very high particle loadings. Moreover, the LC domains show a temporal evolution into a space-spanning network of cellulose spherulites. The evolution process largely depends on the particle concentration, with highly loaded samples showing quicker evolution, which leads to a violation of the CW criterion. Furthermore, the temperature-induced microstructural transition (with and without shear) is also examined.

Role of Colloidal Particles as Scavengers of Groundwater Arsenic: A Case Study from Rural Bengal

Elevated arsenic (As) in groundwater is a well-known phenomenon in the Bengal delta plain (BDP). It has been found that mobilization of As can be influenced by the presence of dissolved organic carbon (DOC) and other mineral phases (specially Fe). In this study, groundwater samples were filtered through varying pore size membrane filters to investigate the fractional distribution of As associated with colloids. Arsenic was found to be associated with colloidal particles having organic matter and Fe mineral phases. This finding is very important for explaining the release mechanism of groundwater As, because such data did not exist with respect to BDP, related to the dissolved phase/colloidal retention of As. This study shows that it would be better to consider the dissolved and colloidal phases as potential scavengers of As when assessing its mobilization or mitigation.

Spatial moments for colloid-enhanced radionuclide transport in heterogeneous aquifers

We consider colloid facilitated radionuclide transport by steady groundwater flow in a heterogeneous porous formation. Radionuclide binding on colloids and soil-matrix is assumed to be kinetically/equilibrium controlled. All reactive parameters are regarded as uniform, whereas the hydraulic log-conductivity is modelled as a stationary random space function (RSF). Colloid-enhanced radionuclide transport is studied by means of spatial moments pertaining to both the dissolved and colloid-bounded concentration. The general expressions of spatial moments for a colloid-bounded plume are presented for the first time, and are discussed in order to show the combined impact of sorption processes as well as aquifer heterogeneity upon the plume migration. For the general case, spatial moments are defined by the aid of two characteristic reaction functions which cannot be expressed analytically. By adopting the approximation for the longitudinal fluid trajectory covariance valid for a flow parallel to the formation bedding suggested by Dagan and Cvetkovic [Dagan G, Cvetkovic V. Spatial Moments of Kinetically Sorbing Plume in a Heterogeneous Aquifers. Water Resour Res 1993;29:4053], we obtain closed form solutions. For illustrative purposes, we consider the case when sorption/desorption between solution and moving colloids is a linear non-equilibrium process, whereas sorption onto the soil-matrix is a linear equilibrium process. Based on the flow and transport parameters pertaining to the alluvial aquifer at the Yucca Mountain Site (Nevada), we investigate the potential enhancing role of colloidal particles by comparing radionuclide spatial moments with and without colloids, and mainly investigate the sensitivity to the reverse rate parameter. The most potentially significant effects are obtained when radionuclide attachment to colloidal particles is irreversible. The simplicity of our results makes them suitable for quick assessments of the potential impact of colloids on contaminant transport in heterogeneous aquifers.

On the role of colloidal particles in light scattering in the ocean

We calculated the optical scattering and backscattering coefficients for assemblages of marine colloids from the measured size distribution and the assumed refractive index of colloids. The comparison of pure seawater scattering and backscattering coefficients with our results from 11 samples of small colloids (sized between 0.01 and 0.2 µm) and 10 samples of large colloids (~0.4™1 µm) suggests that (1) the role of colloids in light scattering in the ocean can vary from insignificant to very important as a result of variations in the concentration, size distribution, and refractive index of particles; (2) whereas small colloids generally play an insignificant role in particulate scattering, large colloids can make a sizable contribution because their scattering can exceed that of pure water by more than an order of magnitude; and (3) small colloids appear to play an important role in the overall colloidal backscattering. The combined backscattering of small and large colloids is typically higher than that of pure seawater over most of the visible spectrum (e.g., by a factor of 2.5 at 550 nm and 5.6 at 700 nm from our average results). This indicates that the contribution of colloids to the particulate backscattering is typically significant.

The role of colloidal particles in the speciation and analysis of “dissolved” phosphorus

Colloidal-sized particles (1–1000nm) and high molecular mass material play an important, yet poorly understood role in the aqueous speciation of P. This study assessed the size distribution of P in 0.45-μm filtered soil solutions and soil–water extracts from three sandy soils (grassland, arable field and forest) using gel filtration chromatography (GFC) and membrane filtration (0.22- and 0.025-μm pore-size) and evaluated the impact of P speciation on colorimetric and ion-chromatographic methods for orthophosphate analysis. Between 40% and 58% of molybdate reactive P (MRP) and >85% of molybdate unreactive P in the soil solution from the agricultural soils (pH 5.9–6.3) were associated with high molecular mass material (apparent size >0.025μm, or >600kDa on Superdex). In solutions from the forest soil (pH 3.2), high molecular mass P (HMMP) compounds were of minor importance (<8% of TP). The GFC elution profiles, composition and spectral characteristics of HMMP-containing solutions as well as the small relevance of HMMP at low pH were all indicative for associations between humic substances, Fe and/or Al, and P. Both MRP and ion chromatographic P measurements overestimated the free orthophosphate concentration (up to 2.3- and 1.4-fold, respectively) in 0.45-μm filtered HMMP-containing solutions. In 0.025-μm filtrates, free orthophosphate was the only MRP species present.

Temporal variations in the fractionation of the rare earth elements in a boreal river; the role of colloidal particles.

Rare earth element (REE) data from weekly sampling of the filtered (<0.45 μm) and suspended particulate phase during 18 months in the Kalix River, Northern Sweden, are presented together with data on colloidal particles and the solution fraction (<3 kDa). The filtered REE concentration show large seasonal and temporal variations in the river. Lanthanum varied between approximately 300 and 2100 pM. High REE concentration in the filter-passing fraction is related to increased water discharge and there is a strong correlation between the REE concentration, organic carbon, Al and Fe. Physical erosion of detrital particles plays a minor role for the yearly transport of particulate REE in this boreal river system. The suspended particulate fraction, which is dominated by non-detrital fractions, accounted for only 35% of the yearly total transport of La in the river. Approximately 10% of the REE were transported in detrital particles during winter. At spring-flood in May, about 30% of the LREE and up to 60% of the HREE where hosted in detrital particles. Ultrafiltration of river water during spring-flood shows that colloidal particles dominate the transport of filter-passing REE. Less than 5% of the filtered REE are found in the fraction smaller than 3 kDa. The colloidal fraction shows a flat to slightly LREE enriched pattern whereas the solution fraction (<3 kDa) show an HREE enriched pattern, compared with till in the catchment. Suspended particles show a LREE enriched pattern. Data indicate that the REE are associated with two phases in the colloidal (and particulate) fraction, an organic-rich phase (with associated Al–Fe) and an Fe-rich (Fe–oxyhydroxide) inorganic phase. The Ce-anomaly in the suspended particulate fraction in the river shows systematic variations, and can be used to interpret fractionation processes of the REE during weathering and transport. There was no anomaly at maximum spring-flood but during the ice-covered period the anomaly became more and more negative. The temporal and seasonal variations of the Ce-anomaly in the suspended particulate phase reflect transport of REE–C–Al–Fe-enriched colloids from the upper section of the till (and/or from mires) to the river at storm events.

ChemInform Abstract: The Role of Colloidal Particles in the Photodegradation of Organic Compounds of Environmental Concern in Aquatic Systems

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The role of colloidal particles in the photodegradation of organic compounds of environmental concern in aquatic systems

Aquatic components which can be active in the photochemically induced transformation of organic compounds include colloidal and sedimentary oxides and Sulfides, and organic colloids, either xenobiotic or naturally occurring. Particular attention is devoted to the degradation processes taking place at the semiconductor/water interface. The possible application of these photocatalytic degradation processes to water purification is outlined.