Foam Texture Research Articles

Application of yellow mustard gum‐fenugreek mixed gum in preparation of non‐dairy fat whipping cream

SummaryYellow mustard gum (YMG) and fenugreek gum (FG) are both natural hydrocolloids derived from plant seeds. They showed synergistic effects of increased viscosity upon mixing thus expanding their applications. In this study, a synergistic YMG‐FG (7:3) blend of different total gum concentrations (0%, 0.05%, 0.1%, 0.15%, 0.2% and 0.25%, w/w) was used to develop a whipping cream formula with dairy fat replaced by palm kernel oil. Whipping creams of both liquid emulsion and whipped cream were characterised in terms of particle size, rheological properties, whippability and foam stability, texture and microstructure. The liquid emulsion before whipping showed a shear‐thinning behaviour regardless of the gum concentration. Upon whipping, the overrun of whipped cream decreased while the foam stability increased with increasing gum mixture content. The whipped cream with the addition of gum mixture retained the shape after storing overnight at 22 °C in comparison with two collapsed commercial samples. The whipped cream with 0.1% gum mixture exhibited optimal foam stability and textural properties among all the samples. Overall, the synergistic blend of YMG‐FG can be used as a natural stabiliser in formulating non‐dairy fat whipping cream products to improve foam stability and airy/fluffy texture.

CO2 foam structure and displacement dynamics in a Hele–Shaw cell

The substitution of CO2 gas with CO2 foam for improved mobility control has recently attracted research attentions in enhanced oil recovery (EOR) as well as aquifer and soil remediation. However, the interplay between CO2 foam properties and oil displacement remains less investigated. In this work, using clear visualizations, we systematically investigate the dynamic advection-dominated foam morphology, its corresponding viscosity, and the efficiency and dynamics of oil displacement process by CO2 foam in a Hele–Shaw cell under the effects of gas ratio (Rg), fluid injection rates (Qt), and surfactant type. Clear visualization enables particle image velocimetry to calculate actual, rather than nominal, foam velocity that significantly affects the estimated foam viscosity. Our results demonstrate that at elevated gas ratios under constant total injection rate, larger and more uniform bubbles with less number density and greater interfacial area are obtained. Increasing the injection rates leads to finer foam texture at a constant gas ratio. Different foam structures have an impact on the foam viscosity, with a general increasing trend of viscosity for larger bubbles as Rg increases from 0.5 to 0.85. The higher the foam viscosity, the more stable displacement interfaces with less viscous fingers are observed, leading to improved sweeping rates. The green surfactants (saponin + Cellulose NanoFibers) provide foams with higher viscosity and, thus, more stable displacement interfaces. These findings highlight the important effect of Rg–dependent foam structure on its viscosity, which in turn is crucial for controlling the mobility of CO2 foam to maximize oil recovery rate during EOR processes.

On Mapping Local Foam Mobility in Porous Media from Computed Tomography Data

Summary Recovering apparent viscosity and foam texture fields from coreflooding experiments is challenging, even with modern computed tomography (CT) scan equipment. In this work, we present an explicit expression for efficiently calculating effective foam viscosity and propose an improved procedure for processing CT scan images to obtain accurate water saturation profiles. Using these techniques, we processed data from a CT scan of a coreflooding experiment, showing that the increase in effective foam viscosity due to foam generation occurs early during injection and before breakthrough. The fast increment in apparent viscosity is due to foam generation before breakthrough. After breakthrough, foam texture reaches its maximum, and effective foam viscosity grows logarithmically over time as the foamed gas sweeps out the water phase. The pressure drop obtained by using the effective foam viscosity showed good agreement with the experimentally obtained values before breakthrough. The workflow proposed here could be readily adapted to other foam models, provided reasonable estimates for these new quantities can be determined from experiments.

Optimization of microwave-produced coal-derived char insulation foam using response surface methodology

A new char-based insulation foam (CIF) is developed using coal-derived pyrolysis char (PC) and lignin, a paper and pulp industry byproduct. In this study, CIF is prepared by adopting the microwave method and Response Surface Methodology (RSM) is utilized to optimize predictions about the properties such as thermal conductivity, foam texture, compressive strength, and pore distribution of CIF. The three independent variables including percent char content, lignin/char ratio, and foaming agent/polyol ratio are considered in the RSM methodology. The face-centered central composite design is selected to obtain 17 test runs. Optimization of the predicted responses is performed to find the recipe considering a composite desirability function. Confirmatory test results show agreement between the predicted and observed values, with the percent error ranging from 0.00 % to 11.35 %, thereby confirming the accuracy of the prediction equations. The optimized CIF exhibits a thermal conductivity of 0.0633 W/m.K and a compressive strength of 695 kPa making it comparable to or better than traditional building insulation products such as fiber insulation, polymer composite, particle board, and ceramic glass foam. Therefore, this new CIF has the potential to be used as an energy-saving insulation material for building envelopes.

Nature and origin of primary ore-forming fluids in the highly metamorphosed Archean Hongtoushan VMS deposit, North China: Insights from in situ S isotopes and trace elements of sulfides

Many ancient volcanogenic massive sulfides (VMS) deposits underwent various degrees of deformation and metamorphism, which modified the primary orebody geometries and sulfide textures, resulting in the great challenge of revealing the source and physicochemical properties of primary ore-forming fluids and original mineralization processes. Here, we observed the textural evolution of sulfides in the highly metamorphosed Archean VMS Hongtoushan Cu-Zn deposit, China, to constrain the histories and P-T conditions of metamorphic remobilization and to evaluate the influence of metamorphism on geochemical characteristics of sulfide. Further, the in situ sulfur isotopic and trace elemental analyses were utilized to reveal the source and physicochemical conditions of initial fluids. During metamorphism, pyrite developed elongated texture, bulging recrystallization, coarse porphyroblasts, and foam texture. These textures all occurred at a temperature of 550 – 700 °C, at which sulfide remobilization and deformation occurred in an anhydrous environment. The geochemical exchange among sulfides did not happen during metamorphism. The sulfur isotope and trace elements of sulfides thus can be used to track the source and physicochemical properties of primary ore-forming fluids. In situ sulfur isotopic analyses of sulfides yielded values of δ34S approaching zero and Δ33S situating mass-dependent isotope fractionation (MDF) area, indicating that the sulfur of the original submarine hydrothermal system was mainly derived from the magmatic fluids. The content of Se in pyrite revealed the primary fluids were acidic and reductive and were used to constrain the temperature of ore-forming fluids, which was higher than 250 °C. The ratio of Co/Ni of pyrite was higher than 10, indicating primary fluids were of magmatic-hydrothermal origin. The high content of Se and As in pyrite and Cd and Hg in sphalerite documented that these elements were partially derived from the magmatic volatiles or magma degassing process. Overall, our study demonstrates that coupling textures and in situ geochemical features of sulfides could be a helpful tool for tracking the primary ore-forming processes of the metamorphosed massive sulfide deposits.

Modeling Microscale Foam Propagation in a Heterogeneous Grain-Based Pore Network with the Pore-Filling Event Network Method

Foam flooding is an efficient and promising technology of enhanced oil recovery that significantly improves sweep efficiency of immiscible displacement processes by providing favorable mobility control on displacing fluids. Although the advantages in flexibility and efficiency are apparent, accurate prediction and effective control of foam flooding in field applications are still difficult to achieve due to the complexity in multiphase interactions. Also, conventional field-scale or mesoscale foam models are inadequate to simulate recent experimental findings in feasibility of foam injection in tight reservoirs. Microscale modeling of foam behavior has been applied to further connect those pore-scale interactions and mesoscale multiphase properties such as foam texture and the relative permeability of foam banks. Modification on a microscale foam model based on a pore-filling event network method is proposed to simulate its propagation in grain-based pore networks with varying degrees of heterogeneity. The impacts of foam injection strategy and oil-weakening phenomena are successfully incorporated. Corresponding microfluidic experiments are performed to validate the simulation results in dynamic displacement pattern as well as interfacial configuration. The proposed modeling method of foam propagation in grain-based networks successfully captures the effects of lamellae configurations corresponding to various foaming processes. The results of the simulation suggest that the wettability of rock has an impact on the relevance between reservoir heterogeneity and the formation of immobile foam banks, which supports the core idea of the recently proposed foam injection strategy in tight oil reservoirs with severe heterogeneity, that of focusing more on the IFT adjustment ability of foam, instead of arbitrarily pursuing high-quality strong foam restricted by permeability constraints.

The Effect of Multiple Cycles of Surfactant-Alternating-Gas Process on Foam Transient Flow and Propagation in a Homogeneous Sandstone

Summary Years of laboratory studies and field tests show that there is still uncertainty about the ability of foam to propagate deep into a reservoir. Many factors have been identified as potential causes of nonpropagation, the most concerning being the lack of sufficient pressure gradient required to propagate foam at locations far from the point of injection. Most researchers that investigated foam propagation did so by coinjecting surfactant and gas. Coinjection offers limited information about transient foam processes due to limitations in the experimental methods needed to measure foam dynamics during transient flow. Foam injection by surfactant-alternating-gas (SAG) has proven to be more effective and common in field application. Repeated drainage and imbibition cycle offer a more favorable condition for the quick generation of foam. Foam can also be propagated at a lower pressure gradient in SAG mode. The objective of this study is to experimentally investigate how transient foam dynamics (trapping, mobilization, and bubble texture) change with multiple cycles of SAG and also with distance from the point of injection. A pair of X-ray source and receiver, differential pressure transducers, and electrical resistance sensors were placed along a 27-cm long, homogeneous, and high-permeability (KL = 70 md) Berea sandstone core. Foam was then generated in situ by SAG injection and allowed to propagate through the core sample under a capillary displacement by brine (brine injection rate = 0.5 cm3/min, Nca = 3×10-7). By use of a novel analytical method on coreflood data obtained from axial pressure and saturation sensors, we obtained trapped foam saturation, in-situ foam flow rates, apparent viscosities, and inferred qualitative foam texture at different core sections. We then observed the following: (i) Maximum trapped foam is uniform across the core sections, with saturation ranging from 47% to 52%. At the vicinity of foam injection, foam apparent viscosity is dominantly caused by gas trapping. At locations farther away, foam apparent viscosity is dominated by both gas trapping and refinement of foam texture. (ii) Cyclic injection of foam further enhances the refinement of foam texture. (iii) Textural refinement increases foam apparent viscosity as it propagates away from the point of injection. (iv) As the foam strength increases, the average gas flow rate in the core sample decreases from 0.5 cm3/min to 0.06 cm3/min. (v) There is no stagnation of foam as remobilization of trapped gas occurs during each cycle at an average flow rate of 0.002 cm3/min.

Interactions between humulinone derived from aged hops and protein Z enhance the foamability and foam stability

Foam is one of the important characteristics of beer, including foamability, foam stability and foam texture. Protein Z (PZ) is considered to be an important component of beer foam. In this study, the interaction between PZ and humulinone, a widespread compound in aged hops, and the effect on foam properties of PZ were investigated. The fluorescence spectra showed that the stoichiometric ratio of humulinone to PZ was 4.25 ± 0.48: 1, and the binding constant was (1.64 ± 0.17) × 105 M−1. MD and FTIR results showed that the main force of interaction between PZ and humulinone was hydrogen bond, and the possible sites were Asn-37, Ser-292, Lys-290 and Pro-395. Moreover, the addition of humulinone greatly reduced the surface tension of PZ solution, and changed the secondary structure of PZ, which is beneficial for the foam stability. Under the influence of humulinone, the foamability, foam stability and foam texture of PZ all increased.

Effects of velocity on N2 and CO2 foam flow with in-situ capillary pressure measurements in a high-permeability homogeneous sandpack

The effects of velocity and gas type on foam flow through porous media have yet to be completely elucidated. Pressure drop and capillary pressure measurements were made at ambient conditions during a series of foam quality scan experiments in a homogenous sandpack while foam texture was simultaneously visualized. New insights into foam-flow behavior in porous media were discovered. Previously accepted “limiting” capillary pressure theory is challenged by the findings in this work, and the “limiting” terminology is replaced with the word “plateau” to reflect these novel observations. Plateau capillary pressure {(P}_{c}) and transition foam quality were found to increase with velocity. Transition foam quality was found to depend mostly on liquid velocity rather than gas velocity and is physically linked to foam type (continuous vs. discontinuous) and texture (fine vs. coarse). Distinct rheological behaviors also arose in the low- and high-quality foam regimes as a function of velocity. Foam flow was found to be strongly shear thinning in the low-quality regime where foam texture was fine and discontinuous. In the high-quality regime, the rheology was weakly shear thinning to Newtonian for coarsely textured foam and continuous-gas flow respectively. When all other variables were held constant, at ambient conditions, CO2 foam was found to be weaker with also lower capillary pressures than N2 foam and the differences in gas solubility is a likely explanation.

A systematic investigation of the relationship between properties of bulk foam and foam in porous media

Bulk foam analysis (static test) is simple and fast, which makes it a cost-effective method for screening and ranking hundreds of surfactants being considered for foam applications. Coreflood tests (dynamic test) can also be used, but it is quite laborious and costly. However, previous reports show that ranking based on static tests sometimes differs from ranking based on dynamic tests. To date, the reason for such a discrepancy is not well understood. Some believe that it may be due to faulty experimental design while some others believe that there is no discrepancy if the right foam performance indices are used to describe and compare the results from both methods. For the first time, this study reports a systematic series of static tests conducted on different foaming solutions (with surfactant concentration ranging from 0.025 to 5 wt%) and duplicated in dynamic tests using the same core sample for all the surfactant solutions. The dynamic test was also repeated on three different rocks of a wide permeability range (26–5000 mD) for each of the surfactant solutions. Unlike previous studies, here multiple dynamic foam indices (limiting capillary pressure, apparent viscosity, trapped foam, and trapped to mobile foam ratio) were measured and compared with the performance indices measured from the static tests (foam texture and foam half-life). Dynamic tests were in total agreement with static tests for all the foam formulations. However, it was observed that the pore size of the base filter disk used in the static foam analyzer can be a potential source of conflicting results when comparing with dynamic test. This is because a threshold pore size exists above which some foam properties (apparent viscosity and trapped foam) significantly decreased compared to the properties before that threshold. Foam limiting capillary pressure is the only foam property that does not show such a trend. It also appears that such threshold occurs above a certain surfactant concentration (0.025 wt%). Apparently, it becomes imperative that the pore size of the filter disk used in the static test and the porous medium used in dynamic tests must be on the same side of the threshold point, otherwise there may be disparity in their results. The threshold surfactant concentration should also be determined. The role of these two factors (pore size and surfactant concentration) requires further investigation.

The effect of rock permeability and pore structure on foam in carbonate rocks

Foam is considered a successful method for providing conformance control during enhanced oil recovery. It helps reduce gravity segregation, viscous fingering, and minimizes injected fluid loss into high permeability zones. Foam rheology has been studied and well understood in sandstones but its behavior in carbonate rocks is not well defined. This study aims to quantify the impact of pore properties represented by permeability, pore throat size (dT), pore body size (dB) and aspect ratio (R) on foam rheology in carbonate rocks. The results are contrasted with foam rheology in natural sandstone rocks. The studied carbonates possess complex pore structures, with bimodal distributions of pore throat and pore body sizes. Pore properties were shown to affect the magnitude of foam viscosity (μa)-foam quality relationship, but the observed trend is unchanged in different rocks. μa was found to linearly correlate with (dT2) and permeability. It was shown to increase exponentially with dB with a marked increase at dB > 30 μm. All the carbonates had aspect ratios R ≫ 2.5 indicating plentiful foam germination sites. As a result, the aspect ratio does not correlate strongly with μa. Pore structure properties were shown to have a strong impact on the μa-shear rate (γ̇a) relationship, by directly impacting the magnitude of both μa and γ̇a, and also by influencing the foam texture. Finally, pore properties were shown to impact factors governing foam transient behavior. Rocks with smaller (dT) are shown to have weaker foam generation and propagation, as well as a larger specific surface area leading to larger dynamic adsorption. Overall, the results of this work indicate that the successful implementation of foam for mobility control in carbonate reservoirs will depend on a good understanding of the rock pore structure.

Salt-templated graphene nanosheet foams filled in silicon rubber toward prominent EMI shielding effectiveness and high thermal conductivity

Lightweight and multifunctional polymer-based composites with prominent electromagnetic interference (EMI) shielding effectiveness (EMI SE) and heat conductance are in urgent demand for developing highly integrated electronic devices in the 5G/6G era. Herein, ultrathin graphene nanosheet-based foams with many micropores are prepared by a general salt-template guided freeze-drying-calcination route with PEG 20000 and NaCl as a carbon source and a template, respectively. Calcination temperature (T) and PEG 20000/NaCl mass ratio (λ) were employed to modulate the texture, defects, graphitization, EM parameters, EMI SE, and thermal conductivity of graphene foams. The graphene foams formed under T = 800 °C and λ = 0.530 exhibited the optimal EMI SE and thermal conductivity. The EMI SE is beyond 20 dB over C, S, and Ku wavebands with a low filling ratio of 7 wt%, exceeding most graphene-based materials. Meanwhile, three-dimensional (3D) interconnected frameworks reduce inter-nanosheet contact thermal resistance and provide continuous frameworks for thermal and electrical conduction, engendering a larger heat conductivity (3.26–3.95 W m−1 K−1) under a lower filling ratio (3–5 wt%) compared to most reported composites. Together with their high SBET (255.6–670.5 m2 g−1) and light weight, the graphene foams synthesized in this research are expected to be utilized as a thermally conductive and EMI shielding filler for advanced electronic packaging.

Complex displacement behavior during foaming gas drainage in 2D microfluidic networks

Foam injection, which can significantly reduce gas mobility and improve sweep efficiency, has been used as an enhanced oil recovery (EOR) technique for decades. In this work, a mechanistic pore network model is proposed to simulate foam propagation in porous media. The model includes wettability through critical pressures for pore filling events and tracks the motion of gas–water interface during foam propagation process. It also allows a quantitative assessment of the thermodynamic and flow properties of foam, such as mobilization pressure gradient, invasion morphology, and foam texture evolution.Our results show that the inclusion of wettability impacts the evolution of the capillary pressure signal, and the mobilization pressure gradient. Both increasing foam texture and reducing contact angle provide a similar effect on the invasion morphology: a transition from the regime of capillary fingering to compact displacement as indicated by fractal dimension and finger width. The effect of disorder depends on its coupling with wettability and foam texture: increasing disorder decreases the pattern compactness; decreasing contact angle or increasing foam texture smooths the gas–water interface, hence increasing compactness, leading to small sensitivity of the emergent pattern to disorder. The comparison between simulations and experiments shows that the proposed model is able to capture the relevant pore-level events that characterize the foaming gas drainage process in a microfluidic device filled with vertical posts and is reliable to be used for providing information needed for parameters in mechanistic foam simulators that are not accessible in conventional laboratory experiments.

Grain boundary networks and shape preferred orientation – A fresh angle on pattern quantification with GBPaQ

A quantitative understanding of grain shape preferred orientation (SPO) and grain boundary networks as fundamental characteristics of rocks and other crystalline solids is of major interest in geology and material science. Grain boundary networks contain useful information on the deformation history of polycrystalline aggregates, and their diagenetic and metamorphic histories. SPO can have a major impact on material characteristics such as permeability, acoustic velocity and mechanical strength, and on reaction surfaces. The objective of this study is to present a semi-automated toolbox of MATLAB™ scripts, named Grain Boundary Pattern Quantification (GBPaQ), that incorporate different methods for grain boundary pattern quantification for their application to, for example, seismic wave attenuation estimation. GBPaQ uses grain boundary statistics and calculates radial scan line intercepts. In this paper, GBPaQ is tested on two example grain boundary patterns, a granular texture and a foam texture with equant grains, which have been digitally stretched (deformed) to analyse their SPO evolution. The results show that a combination of grain ellipse, grain boundary segment orientation, and grain boundary segment intercept density rose diagrams provide a complete, detailed quantification of grain boundary pattern anisotropy. Grain boundary segment intercept (GBSI) analysis using GBPaQ yields a new grain boundary network parameter – the minimum intensity of grain boundary intercepts (Imin) – which follows a power law relationship with the average axial ratio of grain-fitted ellipses (r) during SPO development. We propose that Imin can be used for the quantitative analysis of SPO strength as a useful tool to assess the deformation history of polycrystalline aggregates. Further studies involving a broader range of different patterns and strain histories are necessary to fully investigate the potential of Imin versus r diagrams.

Magnetite texture and trace element evolution in the Shaquanzi Fe-Cu deposit, Eastern Tianshan, NW China

The Shaquanzi deposit is an important Fe-Cu deposit in the Yamansu Fe mineralization belt, Eastern Tianshan. Three types of magnetite were distinguished based on the textural and mineral assemblages, including the platy mushketovite (TA), granular magnetite coexisting with K-feldspar and epidote (TB), and granular magnetite intergrown with pyrite (TC). TA magnetite consists of three generations, including a bright core (TA-1), a dark-gray inner rim (TA-2), and a light-gray outer rim (TA-3), under BSE observations. TA-1 magnetite was transformed from the primary hematite due to a sharply reduced oxygen fugacity and retains its platy pseudomorph. With the changing temperature (increase or decrease), TA-1 magnetite underwent dissolution and re-precipitation (DRP) processes to form TA-2 and TA-3 magnetite. TB magnetite consists of two generations (TB-1 and TB-2). TB-1 magnetite contains abundant mineral inclusions and microporosity. With the decrease of fO2 and temperature, TB-1 magnetite underwent a fluid-assisted recrystallization process to form TB-2 magnetite with foam texture. TC magnetite consists of four different generations (TC-1, TC-2, TC-3, and TC-4). TC-1 magnetite with densely-distributed oscillatory zonings (generally smaller than 1 μm) is surrounded by the darker TC-2 magnetite. TC-2 magnetite with foam texture may be formed by recrystallization of TC-1 magnetite. TC-3 magnetite replaced or cut TC-2 magnetite, indicating that it was formed by the DRP process of TC-2 magnetite. Following periodic changes of fO2 and temperature, TC-4 magnetite with oscillatory zones formed around TC-3 magnetite.This study proposes a new Fe/(Mg + Al + Mn) vs Ti discrimination diagram to distinguish hydrothermal and magmatic magnetite. Magnetite compositions of the Shaquanzi deposit are quite different from those of magmatic magnetite, but very similar to those observed in the hydrothermal system such as IOCG and skarn deposit, indicating that magnetite of the Shaquanzi deposit was formed by hydrothermal process rather than magmatic differentiation.

Effects of Emulsifier Type and Ingredient on the Foam Stability of Meringue

Food foams provide texture and structure for many food products, such as meringues. Meringues, a fundamental of culinary arts, commonly consist of whipped egg white and sugar and have about most of the air phase. These types of composition allow for making different products with the same ingredients; thus, meringue design is essential to investigate foam stability and ability. This study aims to examine the foam stability of meringue using the different components such as protein as emulsifiers (egg white and gelatin) and the composition of sugars (icing and granule) on the foam stability and formation of meringue. Using gelatin as an emulsifier showed the foam more stable than egg white (>24 h), and adding the icing sugar with gelatin made the foam texture smoother. On the other hand, foam formation was faster when using emulsifier egg white, but stability was less than gelatin. The more stable foam produced by the combination of emulsifier and sugar ingredients would provide a better texture of meringue after baking, a smooth surface, no hole, and a more crunchy sweet taste. It was concluded that the composition of the ingredients and type of emulsifier would affect the stability and ability of foam, resulting in the character of the meringue after baking.

Stable and recyclable lanthanum hydroxide–doped graphene oxide biopolymer foam for superior aqueous arsenate removal: Insight mechanisms, batch, and column studies

In this study, a graphene oxide–based lanthanum hydroxide/chitosan foam (CSGOL foam) was synthesized for arsenate (As(V)) remediation in surface water. The synthesized CSGOL foam texture and purity was assessed using scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area, X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) studies. The results proved that the foam was highly porous, stable, and had high surface functionality that facilitated adsorption for water pollutant removal. The sorption results proved that the As(V) removal was high (146.20 mg/g at pH 6 with 0.5 g/L CSGOL foam) when compared to the similar type of materials, endothermic chemisorption due to the production of monodentate and bidentate inner-sphere complexes. Furthermore, continuous column results indicated that the As(V) concentration in real surface waters was reduced to WHO standards (less than 10 μg As/L of water) of As(V) in drinking water for up to 10,000 bed volume. Further it can be used up to four cycles without loss of efficacy less than 93%. Because of its excellent removal capabilities and simple synthesis technique, CSGOL foam shows significant promise for treating As(V)-containing water. Further, the XPS analysis and batch studies results suggests that As(V) removal mechanism was involved electrostatic and surface complexation through chemical interaction predominately.

Experimental Evaluation of Zwitterionic and Cationic Surfactants to Optimize Bulk Foam Properties for Gas Mobility Control in High-Salinity Carbonates

Foam injection has been acknowledged as a promising technology to control gas mobility by establishing the flow resistance during gas enhanced oil recovery (EOR) processes. For applications in challenging carbonate formations, the development of well-matched foaming agents is required. In this paper, the foam performance established by different switchable and zwitterionic surfactants along with their combinations in controlling gas mobility and displacing the residual oil is investigated. The stable solutions of commercial amine-based and/or zwitterionic surfactants were prepared in 20 wt % salinity. A series of foamability and foam stability tests were conducted as initial screening at high temperatures in the presence and absence of crude oil. Foam texture and foam stability were also investigated at different gas/liquid fractions under high-temperature and high-pressure conditions. The best-performing formulation at optimum foam quality was evaluated in coreflooding experiments in terms of mobility reduction factor (MRF) and residual oil recovery. Bulk foam results demonstrated the superior foamability and foam stability of a betaine (B1235) surfactant. Foam endurance of B1235 was found comparable to the diamine (DTTM) produced foam; however, the DTTM surfactant showed insignificant foamability. Among all tested surfactants and their mixtures, B1235 was found most effective in maintaining foam properties in a crude oil environment, and no synergistic effect was observed in the use of surfactant mixtures. The optimum concentrations for B1235 with and without crude oil were 0.25 and 0.5 wt %, respectively. The results obtained from the experiments in a pressurized view cell indicated a prolonged decay profile at 90% gas fraction in bulk. During dynamic flow in carbonate rocks, the optimum quality of foam stabilized by the selected surfactant was found at 70%. At this quality, the pregenerated foam injection pronouncedly increased the MRF to 48. The cumulative oil recovery after foam injection was 67%, providing 25% incremental recovery. The overall performance of the betaine-based surfactant-stabilized foam in high-salinity carbonates was found effective in controlling the gas mobility during the foam EOR process.

Bubble-growth regime for confined foams: Comparison between N2–CO2/foam and CO2/foam stabilized by silica nanoparticles

The use of foam technology in Pre-Salt reservoirs is a potential solution to control gas mobility in highly heterogeneous reservoirs. However, achieving stable CO2-foams under reservoir conditions can be challenging since high solubility in water of supercritical CO2 enhances coarsening and coalescence of bubbles. Coarsening is the evolution of foam structure with time due to gas diffusion between bubbles. In this phenomenon, gas normally diffuses from smaller to larger bubbles, which for confined foam is relevant because this ends up decreasing the number of bubbles in a determined area/volume of the pore space (foam texture). When foam texture coarsens, gas mobility control is impaired, and it can also affect foam rheology. Therefore, it is important to characterize bubble growth kinetics to compare strategies to reduce coarsening and investigate their impact on gas mobility reduction due to foam injection. In a previous work, we reported the use of nanoparticles and a CO2/N2 gas mixture as strategies for improving gas mobility of CO2-foams formed with a zwitterionic surfactant in a micromodel experiment. The present study focuses on quantitatively assessing the bubble growth regime related to coarsening for these two strategies. Indeed, bubble growth is a key parameter for population balance mathematical models that simulate CO2-foams in porous media. Image analysis was used to characterize the foam texture by calculating the bubble density and bubble size distribution of the foam confined in dead-end pores areas of the micromodel. Our results showed that, the number of trapped bubbles was twice as high for the foam formed with the gas mixture compared to those containing nanoparticles, and this higher bubble density was correlated with the higher pressure drop observed for this system, indicating lower gas mobility. The coarsening rates obtained by analyzing the change in trapped bubble area with time of CO2-foam containing nanoparticles (0.25 μm2 s−1) was in the same order of magnitude compared to that obtained by a CO2/N2 gas mixture-foam (0.44 μm2 s−1), under the same high-pressure high-temperature (HPHT) conditions. These results meant that both strategies were able to stabilize the weak foam formed between zwitterionic surfactant and CO2, and that the initial foam texture determined resistance to flow. The semi-automatic algorithm successfully identified the bubbles trapped within the system during the period of analysis, which allowed us not to add dyes that could change interfacial behavior at the water-gas interface. The novel results that evaluate the coarsening rate for CO2-foam under HPHT conditions can positively impact the estimation of foam destruction parameters for population balance models for more representative reservoir conditions of trapped gas. Our findings fill part of the gap in terms of evaluation of coarsening rate under more representative reservoir conditions, improving the understanding of kinetics of foam destruction. This information is relevant for establishing a correct range of the destruction term for populational balance models. Moreover, our results reveal that the type of strategy chosen to delay coarsening can significantly impact gas mobility reduction and that using nanoparticles impacted significantly interfacial properties of the formed foam.

Enhancing N[formula omitted] and CO[formula omitted] foam stability by surfactants and nanoparticles at high temperature and various salinities

To keep up with the ever-growing global energy demand, the petroleum industry has shifted its attention to enhanced oil recovery (EOR) methods, which ensure 30%–60% of residual oil recovery following primary and secondary recovery processes. Foam injection is one of these methods. Due to their low sensitivity to gravity and permeability heterogeneities which improve sweep efficiency, foams are preferable injection fluids than water or gas. However, this recovery technique is not widely used due to the thermodynamic instability of foams. This work aims to take advantage of recent breakthroughs in nanoparticles engineering to build long-lasting nanoparticle-stabilized foams, as nanoparticles can withstand high temperatures and reservoir conditions for a prolonged time. Therefore, to achieve this goal, a comprehensive set of screening experiments was conducted, which included an investigation of the influence of ionic surfactants on foam stability with and without silica nanoparticles at room and elevated temperatures, as well as bulk foam tests with air, nitrogen, and CO2, characterization of foaming suspensions, and analysis of foam texture and morphology. The half-life duration, foam quality, and foam composite index were used to determine the stability of the generated foams. The findings demonstrated that the addition of 0.05% silica nanoparticles could improve the half-life of nitrogen and CO2 foam up to 13% and 40%, respectively. However, the extent of this depends on temperature, salinity and optimal concentration of nanoparticles. Furthermore, the results showed that optimal concentrations of nanoparticles and surfactants should be carefully determined in order to achieve a positive synergistic effect. Results illustrated that selected nanoparticles–surfactant formulations appear very promising for EOR as they show high stability at elevated temperatures and tolerance to different mineralization.