Surfactant Water Research Articles

”Increasing oil recovery by injecting an air composition of the surface active substance (SAS) in the irrigated layers”

The introduction of a water-gas mixture into the reservoir necessitates gas production along with oil in the field. This creates difficulties in the old fields of Azerbaijan. Therefore, unlike the water-gas mixture injected into the layers, the use of a solution of surfactant (SAS) in water instead of air water instead of gas guarantees that the process is both cheap and effective. During the injection of the mixture, the air, being a non-wet phase, will enter the small permeable pores of the layer, helping to displace the oil from it, as well as prevent the formation of water tongues in the layer. The solution from the SAS reagent to be added to the water will not only increase the oil-washing capacity, but also relieve the surface tension at the border with the oil, causing weakening of the capillary forces. Thus, the impact coverage of the reservoir will increase, which will ensure the rise of the oil recovery of the reservoir. By replacing the injection of water with the injection of a solution-air composition through an injector to remove residual oil from the irrigated reservoir, the oil yield coefficient increased by 27%. The injection of the solution-air composition through the reservoir injector increased the oil recovery and also led to a decrease in the volume of the outgoing water.

Experimental investigation of the impacts of supercritical carbon dioxide on acid-etching fracture morphology and conductivity in tight carbonate reservoir

Carbon dioxide (CO2) as energized fluid has been used for acid-fracturing in tight carbonate reservoir. CO2 is often pumped into the wellbore in liquid phase with acid systems, and transited into supercritical state under the high-temperature formation. While the effect of supercritical CO2 (SC-CO2) on acid-etched fracture morphology and conductivity have rarely been investigated. The acid-etching and conductivity experiments were conducted on the outcrops of the Ma5 sub-member of the Ordo Basin in China. The mixed phase reaction simulation device was developed firstly. These experiments involved the mixing of SC-CO2 with various fluids, including formation water and viscoelastic surfactant (VES) acid, as well as different SC-CO2 concentrations with VES acid. The results show that 100 % SC-CO2 is easy to activate natural fractures without dissolution. After 20%SC-CO2 mixed with formation water, the dissolution ability of the mixed solution and conductivity is only 11.8 % and 1 ∼ 2 % of VES acid respectively. Roughness of the morphology created by the mixture of SC-CO2 with VES acid, exhibits a reduction compared to VES acid-etching, accompanied by the presence of wormholes. Additionally, there is a decrease in conductivity and increase in its retention rate. With the increase of SC-CO2 concentration, the roughness of acid-etching fracture decrease and the injection pressure curve becomes more stable. While the reaction rate is also retarded nearly linearly as the SC-CO2 concentration increases. Especially, when the SC-CO2 concentration is up to 40 %, the acid-rock reaction rate reaches only 55 % of that of VES acid. The conductivity of mixed-acid-etched fracture exhibits a segmented characteristic. During the low-medium closure pressure stage, the acid-etched fracture by VES acid generates high conductivity, specifically when it is below 34.5 MPa. While the higher the SC-CO2 concentration in the mixed acid is, the greater the conductivity and retention rate are at pressures above 34.5 MPa during high closure pressure stage. The conductivity of SC-CO2 acid-fracturing fracture depends on the non-uniform etching of the acid solution. The increase in SC-CO2 concentration of the mixed acid not only enhances conductivity and retention rate under high closure pressure, but also reduces the acid volume required for acid-fracturing.

Molecular dynamics simulation and experiment study on technology and mechanism of removing oil and water from aluminum chips

The processes and mechanism of removing oil and water from aluminum chips were clarified through thermogravimetric analysis (TGA), scanning electron microscopy (SEM), response surface method (RSM) and molecular dynamics (MD). The results indicate that the cutting fluid loses mass obviously at 200–300 °C and is carbonized above 400 °C. A layered arrangement of water–surfactant–oil is formed. There are strong hydrogen bonds, strong and weak van der Waals (vdW) forces between O—H in surfactant and O atom in water at 1.63, 3.27 and 5.05 Å, respectively. With the increase of temperature, the weak interaction vdW force is vanished, and the hydrogen bond is reduced. The strong vdW force and hydrogen bonds are broken and the layered arrangement of water–surfactant–oil interface is unstable and destroyed above 277 °C. The removal rate of water and oil is up to 99.7% when the chips are heated at 370 °C for 70 min with 3 cm loading thickness.

H-bond network, interfacial tension and chain melting temperature govern phospholipid self-assembly in ionic liquids

HypothesisThe self-assembly structures and phase behaviour of phospholipids in protic ionic liquids (ILs) depend on intermolecular forces that can be controlled through changes in the size, polarity, and H-bond capacity of the solvent. ExperimentsThe structure and temperature stability of the self-assembled phases formed by four phospholipids in three ILs was determined by a combination of small- and wide-angle X-ray scattering (SAXS and WAXS) and small-angle neutron scattering (SANS). The phospholipids have identical phosphocholine head groups but different alkyl tail lengths and saturations (DOPC, POPC, DPPC and DSPC), while the ILs’ amphiphilicity, H–bond network density and polarity are varied between propylammonium nitrate (PAN) to ethylammonium nitrate (EAN) to ethanolammonium nitrate (EtAN). FindingsThe observed structures and phase behaviour of the lipids becomes more surfactant–like with decreasing average solvent polarity, H-bond network density and surface tension. In PAN, all the investigated phospholipids behave like surfactants in water. In EAN they exhibit anomalous phase sequences and unexpected transitions as a function of temperature, while EtAN supports structures that share characteristics with water and EAN. Structures formed are also sensitive to proximity to the lipid chain melting temperature.

Observing zinc oxide nanoparticles suspension stability in various media by using single particle inductively coupled plasma mass spectrometry (SP-ICP-MS)

Zinc oxide (ZnO) nanoparticles are widely used in industry due to their ability to absorb UV light and antibacterial property. The total surface area of ZnO nanoparticles affects its properties and applications. Therefore, the size and stability control of ZnO nanoparticles is very important. We explored the ability of single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) in combination with settling process to analyze ZnO nanoparticles suspended in various media, by which the method allows to detect specific nanoparticles at very low concentration. The settling experiment of ZnO nanoparticles suspended in various media, including deionized water, non-ionic, cationic and anionic surfactants, was carried out to study size, stability and dispersion. The SP-ICP-MS along with settling experiment was set up by suspending different sizes of ZnO nanoparticles in deionized water, Triton X-100, cetyltrimethylammonium bromide and sodium dodecyl sulfate, followed by collecting the sample at various times and vertical distances. Then, the collected samples were diluted and analyzed by SP-ICP-MS to obtain the information on particle size distribution and the particle number concentration. The size and morphology of the ZnO nanoparticles were observed by transmission electron microscopy technique and zeta potential values of particles suspension were measured. The total concentrations of Zn in the suspension were also analyzed by conventional mode ICP-MS to compare with single particle mode ICP-MS. The information obtained in this work allows us to assess the stability of ZnO nanoparticles in various media and shows that the newly developed approach based on SP-ICP-MS with settling experiment can be used as an alternative characterization tool to evaluate the stability of nanoparticles.

The aqueous processing of carbon nanofibers via cellulose nanocrystals as a green path towards e-textiles with n-type thermoelectric behaviour

Cellulose nanocrystals (CNCs) are a nanostructured biopolymer with unique properties, such as high strength and water stability. These properties make CNCs ideal for diverse applications, including dispersing agents for hydrophobic carbon nanomaterials in water. Specifically, carbon nanomaterials can be integrated into textiles to produce flexible electronic wearables with excellent performance. However, the necessary prerequisite of achieving stable liquid dispersions of these carbon nanomaterials, such as nanofibers (CNFs) typically involves the use of organic solvents or high concentrations of hazardous surfactants in water. Thus, in this study, for the first time, CNCs were successfully used to prepare CNFs aqueous dispersions, referred to as inks, at CNF concentrations up to 0.7 g L−1. As a proof of principle, these inks were then integrated into a cotton fabric using a facile dip coating and drying strategy, resulting in an e-textile with a negative Seebeck coefficient. Furthermore, a theoretical model was developed to describe the nonlinear Seebeck coefficient of the nanocomposite textile, shedding light on the physics governing the electrical conductivity and Seebeck coefficient over a temperature range from 30 °C to 100 °C. These promising results pave the way towards the development of environmentally friendly and durable CNF aqueous dispersions and wearable e-textiles.

Mechanism and synergic effect of smart water and amphoteric surfactant on oil recovery in carbonate rocks: Marangoni flow and changing disjoining pressure of water film

One way to increase oil production was to inject various water-based fluids to move oil into the reservoirs, which in some cases used surfactants to produce oil trapped in the water-based fluid, but later found that thess materials can change the wettability of the rock surface to the desired, so various mechanisms have been introduced for them. In this study, using CAPB, CTAB SDS and Triton X-100s surfactants, wettability tests (contact angle), interprocess tension, zeta potential between different procedures, video experiments for Marangoni flow and intrusive vampire tried to explain the primary production mechanism. They are dealt with different reactants. The results showed that the cationic surfactant CTAB, due to its positive ionic charge and the presence of electrostatic forces, approaches the fatty acid groups attached to the rock surface with a negative ionic charge and forms a complex of cationic-anionic ion pairs with them. General condition Compared to cationic surfactants, the performance of anionic surfactants on the change in wettability of carbonate rocks is inferior. This is due to the homonymous electric charge of the oil groups adhering to the rock surface and the anionic surfactants of SDS.

Adsorption of anionic dyes onto 1,5-Diphenylcarbazide functionalized magnetic hybrid polymer: Impact of water salinity and surfactants on adsorption isotherms

Herein, an effective hybrid adsorbent based on magnetic chitosan (MC) and magnetic glycidyl methacrylate (Mp(GMA)) was synthesized. The prepared hybrid material was functionalized by 1,5-Diphenylcarbazide (DPC), then employed for the adsorption of two anionic dyes (Coomassie brilliant blue G-250; CBB, and Eosin Y; EO) from their synthetic solutions. The as-fabricated adsorbent (MC-Mp(GMA)/DPC) was specifically investigated via FTIR, SEM-EDX, BET, TGA, and VSM analyses. The influence of several operational key factors; initial solution pH, initial dye concentration, contact time, temperature, and influence of cationic, anionic surfactant, and salinity on adsorption isotherms were investigated. The findings revealed that MC-Mp(GMA)/DPC highest adsorption capacities were recorded in the presence of cationic surfactant (0.795, 0.817 mmol g−1 for CBB and EO, respectively) and salinity hardly affects adsorption isotherms. Moreover, the adsorption process of each dye was reported to fit with the Langmuir model at all conditions, while the PSORE model well-defined their adsorption kinetics. Meanwhile, thermodynamics revealed that the separation of CBB and EO dyes was endothermic. Moreover, MC-Mp(GMA)/DPC possessed a desirable efficacy for the regeneration (e.g., 77.9% and 71.7 for CBB and EO, respectively) up to the 4th cycle, affirming its outstanding renewability. Overall, the produced MC-Mp(GMA)/DPC can potentially be offered as a promising recyclable dye scavenger for wastewater remediation.

Surfactants in waste water: Development, current status and associated challenges

Using soaps, disinfectants, sanitizers, surface cleaners, and detergents on a large scale has increased during COVID-19, making it apparent again to review their scale of usage. Increasing consumption of disinfectants, soaps, and detergents for hygiene enhancement in medical, domestic, and corporate sectors triggers a significant increase in the contaminants in wastewater. Surfactants facilitate cleansing by lowering the surface tension. Surfactants, the main ingredients of soaps, detergents, and cleansing agents, impart different properties to the cleansing systems. Surfactants are used as substrates in the synthesis of various products, including dyes, pigments, pesticides, exchange resins, plasticizers, and pharmaceuticals, along with their primary use in household and laundry detergents and cleaners, cosmetics, textile and tanning industry, paints, preservative coatings, pulp and paper, and petroleum products. A significant portion of surfactants is let into the water bodies through laundry detergents. The detergent formulations constitute almost 40% of surfactants. The quest for effective detergents and disinfecting properties has led to the pursuit of newer alternatives for surfactant incorporation.The current manuscript represents the journey of surfactants in terms of their development over time, the modifications carried out to impart desired traits, and their hazardous implications. A study on species of Anabas testudineus showed that the fishes are fatally affected by detergent concentrations above 200 mg/L. It further encompasses the proposed alterations to combat the harmful environmental effects. Cationic surfactants were observed to have a more hazardous impacts than anionic and non-ionic surfactants. The manuscript emphasizes the utilization of more environment-friendly substitutes for surfactant molecules. It presents an overview of different molecules which are a part of surfactants, hazardous traits, and prospects associated with different surfactant entities.

Towards compartmentalized micelles: Mixed perfluorinated and hydrogenated ionic surfactants in aqueous solution

HypothesisAqueous solutions of mixtures of hydrogenated and perfluorinated ionic surfactants are known to display anomalous aggregation behavior due to the mutual phobicity between hydrogenated and perfluorinated chains. Despite all efforts, different experimental limitations prevented so far a definite interpretation of the existing experimental results: both intermicellar and intramicellar segregation remain acceptable possibilities. MethodThe potential for segregation of mixtures of fluorinated and hydrogenated ionic surfactants in water was assessed using atomistic molecular dynamics simulations. Aqueous mixtures of hydrogenated and perfluorinated ionic surfactants were studied: mixtures of anionic surfactants (sodium dodecylsulfate (SDS) + sodium perfluoro-octanoate (SPFO)) and catanionic surfactants (decyltrimethylammonium bromide (DeTAB) + SPFO) were simulated. FindingsThe mixture of anionic surfactants, SDS + SPFO, exhibits clear intramicellar segregation between fluorinated and hydrogenated chains, displaying hydrogenous-rich and fluorous-rich regions. Compartmentalized micelles are thus clearly formed. The simulation results also suggest the possibility of intermicellar segregation. Conversely, catanionic mixtures of DeTAB and SPFO in water solution assemble into a large oblate structure, containing all available molecules in the simulation box, resembling a double layer membrane or a vesicle wall. In this case mixing between fluorinated and hydrogenated surfactants is dictated by charge alternation.

Studying the effect of surfactant assisted low-salinity water flooding on clay-rich sandstones

Sandstone reservoirs often contain clay particles that can cause damage and reduce permeability during low-salinity water flooding. In this study, the effect of surfactants on fine migration in clay-rich sandstones and its impact on oil recovery was investigated.First, the impact of surfactants on interparticle forces in fine-matrix, fine-fine, and oil-matrix systems was modeled. The results showed that both CTAB (cetyltrimethyl ammonium bromide) and QS (quillaja saponin) cause EDL compaction, weakening the repulsive forces. However, SDS (sodium dodecyl sulfate) and TX (triton X-100) do not affect the EDL. Next, the effect of surfactants on IFT reduction and wettability alteration was experimentally investigated. All surfactants reduced IFT due to the surface excessive concentration mechanism. The wettability alteration experiment illustrated that although QS and CTAB compact EDL around oil and matrix particles leading to attraction force augmentation, they both alter wettability through adsorption on matrix and carboxylic groups present in crude oil, respectively.Surfactant aqueous solutions were then injected into various clay-rich sandstone sanpacks, which resulted in increased oil recovery. However, the mechanisms leading to enhanced oil recovery variedby surfactant type. CTAB increased recovery by 10% through IFT reduction and wettability alteration, while SDS and TX increased recovery by 12% and 9%, respectively, through wettability alteration and extreme fine migration. In contrast, partial fine migration in the QS flooding experiment reached a recovery increase of 18%. Permeability trends through experiments were also recorded. During CTAB injection, permeability did not reduce, while QS aqueous solution reduced rock permeability to 5 mD. SDS and TX reduced the magnitude of permeability to 2 mD.In conclusion, this study demonstrates that surfactants can effectively improve oil recovery in clay-rich sandstones by altering the interparticle forces, reducing IFT, and changing wettability. The results suggest that the type of surfactant used should be carefully selected to achieve the desired recovery increase without affecting the permeability of the reservoir.

Self-Assembly of the Cationic Gemini Surfactant in Water: From Elastic Gels to Viscoelastic Solutions

Gemini surfactants, composed of two surfactant monomers, are likely to self-assemble into viscoelastic fluids in water at low concentrations. Here, the aggregation behaviors of quaternary ammonium gemini surfactant with a hydroxyl group on the spacer (16-3OH-16) have been studied in the dilute aqueous system by rheological techniques, small angle X-ray scattering (SAXS), scanning electron microscopy (SEM) and other characterizations. At room temperature, the samples behave as elastic gels. The structure and morphology of gels were confirmed by SAXS and SEM characterizations. Due to the hydroxyl group on the spacer of 16-3OH-16, the gels are more stable than those formed by 16-3-16. At high temperature, the gels transform into wormlike micelles and behave as viscoelastic fluids. The obtained results would help to construct complexed fluids with structure tailorable gemini surfactants.

Surfactants in water and wastewater (greywater): Environmental toxicity and treatment options

Surfactant, an emerging pollutant present in greywater, raises the toxicity levels in the water body. Soap, detergent, and personal care items add surfactant to greywater. Due to excessive washing and cleaning procedures brought on by the COVID-19 pandemic, the release of surfactants in greywater has also increased. Considering the environmental toxicity and problems it creates during the treatment, it's essential to remove surfactants from the wastewater. This review intends to explain and address the environmental toxicity of the surfactant released via greywater and current techniques for surfactant removal from wastewater. Various physical, chemical, and biological methods are reported. Modern adsorbents such as hydrophilic silica nanoparticles, chitosan, fly ash, and iron oxide remove surfactants by adsorption. Membrane filtration effectively removes surfactants but is not cost-effective. Coagulants (chemical and natural coagulants) neutralize surfactant charges and help remove them as bigger particles. Electrocoagulation/electroflotation causes surfactants to coagulate and float. Microorganisms break down surfactants in microbial fuel cells to generate power. Surfactants are removed by natural processes and plants in constructed wetlands where traditional aerobic and anaerobic approaches use microbes to break down surfactants. Constructed wetlands, natural coagulation-flocculation, and microbial fuel cells are environmentally beneficial methods to remove surfactants from wastewater.

A Numerical Study on the Multiphase Newtonian and Non-Newtonian Displacement in a Porous Micromodel via Water–Surfactant–Polymer Flooding

A Numerical Study on the Multiphase Newtonian and Non-Newtonian Displacement in a Porous Micromodel via Water–Surfactant–Polymer Flooding

Alkaline Water-Assisted Polyol Synthesis of Pt/Vulcan PEMFC Cathode Electrocatalysts

Sluggish oxygen reduction reaction (ORR) kinetics motivates great focus on PEMFC cathode electrocatalyst development.1 Electrocatalysts based on Pt are often prepared via the so-called polyol process, a solvothermal process that allows controlling of the structure, morphology, and chemical nature of various metal nanoparticles.2 Several parameters have been well-studied and thoroughly discussed in literature over the years, varying from surfactant removal or water addition to pH or NaOH/Pt molar ratio effect on Pt particle size. 3,4 Here, we present a slight modification of the well-established surfactant-free alkaline one-pot polyol synthesis of Pt-nanoparticles on Vulcan XC 72R carbon support and the subsequent PEMFC characterization tests with respect to initial electrochemical performance and standardized accelerated stress tests (AST). In this approach, the solvent composition is systematically changed by the substitution of ethylene glycol to water and by increasing the Pt precursor concentration per mass of solvent to ultimately minimize the amount of ethylene glycol used.The so-synthesized electrocatalyst powders, with Pt particle sizes ranging from 2 to 6 nm, were physico-chemically analyzed by powder X-ray diffraction, thermogravimetric analysis, and transmission/scanning electron microscopy. The initial electrochemical performance as well as the stability were evaluated by implementing membrane electrode assemblies (MEAs), prepared from a series of synthesized electrocatalysts in a differential flow single cell setup (12 cm2). The electrochemical performance of the prepared MEAs was evaluated and compared to a commercial reference catalyst coated membrane (CCM), as well as to an internal reference CCM, that was prepared using a cathode Pt/C catalyst synthesized via pure ethylene glycol-based polyol route.Beginning-of-life MEA data indicate the possibility of reducing the required ethylene glycol amount per mass of synthesized catalyst by up to 98%. Taking catalyst durability as an additional optimization criterion into account, a Pt/C electrocatalyst synthesized with 45 vol% H2O at a Pt precursor concentration of 32 mM, ultimately leading to an ethylene glycol reduction of 90%, showed a decent initial electrochemical performance (716 mV at 1 A cm-2), as well as an AST stability similar to the internal reference (Pt/C synthesized using pure EG and Pt precursor concentration of 16 mM).In summary, we conclude that water content and Pt precursor concentration have a crucial impact on the characteristics of Pt/C electrocatalysts in the modified polyol route. At optimum parameter values, catalysts with optimized electrochemical performance in PEMFC applications can be synthesized, with substantially lowered synthesis cost due to solvent substitution.

Influence of anionic surfactant on stability of nanoparticles in aqueous solutions

Dispersion and aggregation of nanoparticles in aqueous solutions are important factors for safe and effective application of nanoparticles, for instance, in the oil industry. As conventional oil reserves are depleted, it is necessary to advance chemical enhanced oil recovery (cEOR) techniques to develop unconventional oil reservoirs. Nanoparticles modified by surfactants can be a promising reagent in cEOR. These nanomaterials can reduce interfacial tension and change the wettability of reservoir rock, which leads to an increase in oil recovery. However, the application of nanoparticles is limited by their substantial aggregation in aqueous solutions. The purpose of this work is to select nanoparticles for obtaining stable sols in water in the presence of an anionic surfactant and to optimize the conditions (pH) for further modifying the nanoparticles with the anionic surfactant. Sodium dodecyl sulfate (SDS) is used as an anionic surfactant. The aggregation of oxide and carbon nanoparticles in water and anionic surfactant solutions was studied by laser diffraction, dynamic and electrophoretic light scattering methods. Most of the studied nanoparticles in water form aggregates with bi-, three- and polymodal particle size distributions. TiO2 nanoparticles obtained by plasma dynamic synthesis form the most stable sols in anionic surfactant solutions. The range of 5–7 pH is defined as optimal for their modification with surfactants. The stability of carbon nanoparticles in aqueous solutions increases significantly in the presence of a surfactant. The obtained results form the basis for further research on the modification of marked nanoparticles in surfactant solutions.

Experimental and mechanistic study of the surfactant-assisted hydrocyclone desanding of heavy oil

During the thermal recovery of heavy oil, sand is often produced in the formation, and this sand is carried into the surface processing system with high-viscosity heavy oil, which causes serious safety hazards for production facilities and pipelines. Therefore, it is necessary to conduct research on heavy-oil desanding technology to fundamentally eliminate the risks that sand poses to equipment and pipelines. In this study, a heavy-oil desanding experiment was carried out under full consideration of the influence of the water content, temperature and surfactants, and the optimal operating parameter range for achieving a high sand removal rate was identified. The experimental results showed that a high-efficiency desanding effect cannot be achieved by only heating and mixing water and that adding surfactants can significantly improve the efficiency of high-viscosity oil hydrocyclone desanding. To explore the mechanism of surfactant-assisted hydrocyclone desanding, the effect and mechanism of surfactants in promoting high-viscosity oil desanding was analyzed from the perspective of discrete-phase droplet dynamics. The demulsifier promoted the demulsification and stratification of heavy-oil emulsions, the oil droplets formed agglomerates with large particle sizes, and the oil-water phase was rapidly stratified near the vortex finder of the hydrocyclone. Even under a high oil phase viscosity (984 mPa s), the centrifugal field of the hydrocyclone was less affected. At this time, a considerable sand removal rate could be achieved. The viscosity reducer had the same water stratification function as the demulsifier and also promoted the phase inversion of the W/O (water in oil) emulsion to form an O/W(oil in water) emulsion with lower viscosity, significantly reduced the drag force of sand, and greatly improved the sand removal efficiency.

Effect of CO2 Huff-n-Puff Mode with a Horizontal Well on Shale Oil Recovery: A Three-Dimensional Experimental Study

After conventional development, there is still a significant amount of residual oil as a result of the poor porosity and permeability characteristics of shale reservoirs. Although CO2 flooding is one of the most reasonable recovery techniques, it is affected by a serious sweep efficiency issue. In this paper, six CO2 huff-n-puff cooperative combination methods were established with the aid of three-dimensional physical simulation equipment, including CO2 huff-n-puff (HNP), water-disturbance-assisted CO2 huff-n-puff (WD-HNP), surfactant- and water-disturbance-assisted CO2 huff-n-puff (SWD-HNP), pumping-production-assisted CO2 huff-n-puff (PP-HNP), water-disturbance-assisted CO2 huff-n-puff after pumping production (WDP-HNP), and surfactant- and water-disturbance-assisted CO2 huff-n-puff after pumping production (SWDP-HNP). The displacement characteristics, utilization law, and development effect were investigated. CO2 huff-n-puff requires more gas injection quickly, and low permeability and pressure difference can easily cause irregular gas channeling, showing the arc linear flooding pattern. Water disturbance can significantly delay the rapid breakthrough, so that the displacement edge shows the radial flooding pattern. The effect of pumping production on the displacement is not obvious, and the leading edge still shows an oval-shaped flooding pattern. Surfactant assistance improves the gas injection ability, eventually demonstrating a plane steady flooding pattern. In comparison to HNP, the average enhancement degree of water injection disturbance, pumping production, and surfactant assistance to the utilization extent is 6.61, 1.82, and 8.93% respectively. Meanwhile, SWDP-HNP had the highest oil recovery (33.35%) among all modes. By comparison of effective productivity, it revealed that about 12% of the lifting range is helped by surfactant assistance, followed by a water injection disturbance lifting amplitude of 5.5%, while pumping production only led to a 3% improvement. With the combination of all development effect evaluation indicators, SWD-HNP is a reasonable displacement method to improve shale reservoir recovery in this study.

Degradation of trichloroethylene in aqueous solution by FeS2 catalyst under innovative oxic environments

Rapid growth and industrialization have become a major threat to water contamination with carcinogenic chlorinated hydrocarbons such as trichloroethylene (TCE). Therefore, this study aims to assess the TCE degradation performance through advanced oxidation process (AOP) using catalyst FeS2 in combination with oxidants persulfate (PS), peroxymonosulfate (PMS), and hydrogen peroxide (H2O2) in PS/FeS2, PMS/FeS2, and H2O2/FeS2 systems, respectively. TCE concentration was analyzed using gas chromatography (GC). The results found the trend for TCE degradation by the systems was PMS/FeS2>PS/FeS2>H2O2/FeS2 (99.84, 99.63, and 98.47%, respectively). Degradation of TCE was analyzed at different pH ranges (3–11) and maximum degradation at a wide pH range was observed for PMS/FeS2. The analysis using electron paramagnetic resonance (EPR) and scavenging tests explored responsible reactive oxygen species (ROS) for TCE degradation and found that HO• and SO4−• played the most effective role. The results of catalyst stability showed PMS/FeS2 system the most promising with the stability of 99, 96 and 50% for the first, second and third runs, respectively. The system was also found efficient in the presence of surfactants (TW-80, TX-100, and Brij-35) in ultra-pure water (89.41, 34.11, 96.61%, respectively), and actual groundwater (94.37, 33.72, and 73.48%, respectively), but at higher reagents dosages (5X for ultra-pure water and 10X actual ground water). Furthermore, it is demonstrated that the oxic systems have degradation capability for other TCE-like pollutants. In conclusion, due to its high stability, reactivity, and cost-effectiveness, PMS/FeS2 system could be a better choice for the treatment of TCE contaminated water and can be beneficial for field application.

Experimental investigation of surfactant adsorption during EOR and soil pollution control processes: Influence of surfactant concentration, water salinity, and clay type

Surfactant injection is a well-established method of chemical EOR processes. Surfactant adsorption into clay layers can prevent their proper performance and thus reduce the oil recovery factor. On the other hand, this adsorption property of clay materials can be used to prevent surface and underground water pollution and reduce soil pollution. In this experimental study, the effect of surfactant concentration, electrolyte type (NaCl and MgCl2), and the solution salinity on fluid adsorption into the interlayer space of different clay types (bentonite and kaolinite) was investigated. XRF analysis was conducted on two relevant clay samples, and immersion and Washburn tests were performed on the desired samples with the Sigma 700 setup. Then, according to the clay type, the most optimal conditions were introduced for the surfactant solution used in the two areas of EOR and environmental processes related to reducing soil pollution. In the EOR processes, the optimal condition for the lowest adsorption amount is C (with 1 CMC concentration and salinity of 100,000 ppm for NaCl salt). This fluid works better in kaolinite formations. In the environmental field related to the reduction of soil pollution, if the pollutants we are looking for are R and S (with alkyl benzene sulfonic acid as the dominant agent), bentonite has a better performance than kaolinite in terms of adsorption and subsequently pollution control. If the polluting fluid contains MgCl2 ions in the exact salinity values, the adsorption amount and soil pollution control will be higher for both adsorbent clays than if our fluid has NaCl salinity. The study's findings have a wide range of applications in surfactant flooding designs, surfactant adsorption optimization, and can be generalized to other detergent types.