Wettability alteration and reducing water blockage in tight gas sandstone reservoirs using mixed cationic Gemini/nonionic fluorosurfactant mixtures

The unrecovered hydraulic fracturing fluid will invade the matrix and induce water blockage, creating formation damage and hindering the oil or gas production rate. First, the synergistic effect of cationic Gemini surfactant (MQAS) and nonionic fluorosurfactant (N-2821) mixtures on reducing the surface tension and wettability alteration was investigated in this paper. The critical micelle concentration (CMC) of the surfactant mixture is one or two orders of magnitude lower than that of N-2821 and MQAS, indicating that the MQAS/N-2821 mixtures exhibit an apparent synergistic effect in reducing surface tension. Moreover, the maximal contact angle of MQAS/N-2821 mixtures reached 83.55° at α_N-2821 = 0.5, and the total surfactant concentration of 1 × 10⁻⁴ mol/L due to the adsorption of surfactant. The adsorption mechanism of surfactants on the surface of quartz sand was then examined. The adsorption kinetics is consistent with the pseudo-second-order model at different surfactant concentrations, while the Freundlich model is suitable for describing the adsorption behavior of surfactants on the sandstone surface. This finding indicates that surfactant adsorption is multilayered. The MQAS/N-2821 surfactant mixtures have excellent surfactant activity due to the relationship of the capillary pressure to the surface tension, pore radius, and contact angle; thus, the addition of surfactant mixtures can reduce the liquid saturation effectively. Furthermore, the sequential imbibition experiments indicate that MQAS/N-2821 mixtures alter the wettability of the core plug, which results from the adsorption of surfactants. Compared with brine water, the MQAS/N-2821 mixtures decreased the liquid saturation and increased the permeability recovery ratios of the core plug.     

Surfactant-Induced Wettability Alteration of Oil-Wet Sandstone Surface: Mechanisms and Its Effect on Oil Recovery

Different analytical methods were utilized to investigate the mechanisms for wettability alteration of oil-wet sandstone surfaces induced by different surfactants and the effect of reservoir wettability on oil recovery. The cationic surfactant cetyltrimethylammonium bromide (CTAB) is more effective than the nonionic surfactant octylphenol ethoxylate (TX-100) and the anionic surfactant sodium laureth sulfate (POE(1)) in altering the wettability of oil-wet sandstone surfaces. The cationic surfactant CTAB was able to desorb negatively charged carboxylates of crude oil from the solid surface in an irreversible way by the formation of ion pairs. For the nonionic surfactant TX-100 and the anionic surfactant POE(1), the wettability of oil-wet sandstone surfaces is changed by the adsorption of surfactants on the solid surface. The different surfactants were added into water to vary the core surface wettability, while maintaining a constant interfacial tension. The more water-wet core showed a higher oil recovery by spontaneous imbibition. The neutral wetting micromodel showed the highest oil recovery by waterflooding and the oil-wet model showed the maximum residual oil saturation among all the models.     

Surfactant-assisted combustion synthesis of agglomerated-free,size- and shape-controlled magnetic iron oxide nanoparticles for biomedical applications

An advanced version of the solution combustion synthesis (SCS) method was developed to prepare iron oxide (IO) nanoparticles, through controlling the agglomeration, size and shape of nanoparticles by assisting a cationic surfactant, “cetyltrimethylammonium bromide (CTAB)” and ethanol. Various IO nanoparticles were prepared in the presence of different CTAB:ethanol molar compositions of 0:0, 0.27:0, 0.55:0, 0.27:17.1, 0.55:17.1 and 0.82:17.1. The morphological evolution from agglomerated-shape particles to the well-dispersed as well as the size- and shape-controlled particles depended directly on the CTAB:ethanol molar composition. A shift from ferromagnetic behavior to superparamagnetic was observed by the application of CTAB along with ethanol, where the lowest blocking temperature (T_b, 60 K), highest saturation magnetization (M_s, 83.5 emu g⁻¹), zero coercivity and remanance magnetization were revealed for the particles prepared by CTAB:ethanol molar compositions of 0.55:17.1. These particles showed an acceptable specific absorption rate (SAR) value (320 W g⁻¹) as well as no obvious hemolytic and cytotoxic effects. This work provides new insights into advancing the SCS method and thus controlling the morphology, size and shape of metal oxide nanoparticles.     

油基钻井液润湿剂室内研究

在油基钻井液中加入适量的润湿剂,可以使其体系中的惰性固相具有强的亲油性,从而保证油基钻井液体系的稳定性和各种性能的调节及控制。室内对3种润湿剂:阳离子表面活性剂CTAB、生物表面活性剂CQ-WBP、甜菜碱型两性离子表面活性剂CQ-WZB进行表面张力、润湿角测定和重晶石在油相中的沉降实验。实验结果表明,3种润湿剂在改变重晶石等亲水性物质的能力强弱顺序为:CQ-WBPCQ-WZBCTAB。生物表面活性剂CQ-WBP加入油基基浆中,不但能够大幅度改善油基钻井液性能,还具有一定的抗温能力。     

烷基烯酮二聚体对褐煤疏水改性及成浆性能的影响

针对褐煤表面亲水基团丰富、孔隙发达导致煤成浆性能差的问题,以阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）为乳化剂制备了阳离子烷基烯酮二聚体（AKD）乳液,将其涂覆在经微波脱水后的褐煤颗粒表面,使煤样表面获得较强的疏水性;利用比表面积分析仪（BET）、X射线光电子能谱（XPS）和化学滴定法研究了AKD与煤表面的作用机理,同时测定了煤水体系的zeta电位以及煤水界面润湿性,结果表明AKD在煤表面发生了物理化学吸附,并当阳离子AKD乳液用量为1.5%时,改性煤粒表面zeta电位绝对值达到最大,褐煤与水的接触角从50.92°增加到121.10°;再将改性后的褐煤颗粒配合聚萘磺酸盐分散剂制得高浓度的水煤浆,当褐煤水煤浆黏度保持1000mPa·s时,最大成浆浓度从原煤的56.6%增加到61.20%,并且随水煤浆存放时间的延长其水煤浆的黏度保持稳定。     

Geopolymer assembly by emulsion templating: Emulsion stability and hardening mechanisms

This work investigates emulsion templating to synthesize hexadecane oil/geopolymer composites. In a system with hexadecane as the internal (dispersed) phase and an alkali activated continuous phase without added surfactant, adding aluminosilicate clay particles does not increase resistance against creaming or coalescence, while adding a surfactant (L35 or CTAB) stabilizes the solid-liquid interface. Infrared studies and rheological studies of the associated geopolymerization determined that the presence of the organic phase or surfactant has no significant effect on the geopolymerization kinetics, as determined by the change in time of the Si-O-T IR stretching frequency and the rheological moduli involved during the process. The stabilization of the organic template is reminiscent of Pickering emulsion even though we employ a much greater amount of inorganic material for geopolymer formation. Although the addition of surfactant has a significant effect on the behavior of the paste, the percolation of the network remains unmodified, highlighting the fact that the phenomenon is not dependent on viscosity. Finally, rheological measurements were used to obtain the mass fractal dimension of the as-made gel network, which is able to differentiate the interfacial effect between surfactant molecules with a slightly denser interphase when a cationic surfactant is used.     

Emulsion polymerization of tetrafluoroethylene: effects of reaction conditions on the polymerization rate and polymer molecular weight

The emulsion polymerization of tetrafluoroethylene (TFE) was carried out in a semibatch reactor using a chemical initiator (ammonium persulfate) and a fluorinated surfactant (FC-143). The effects of the reaction condition were investigated though the polymerization rate, molecular weight of polytetrafluoroethylene (PTFE), and stability of the dispersion. The emulsion polymerization of TFE was different from conventional emulsion polymerization. The polymerization rate was suppressed when the polymer particles were significantly coagulated. The polymerization rate increased with operating temperature, surfactant concentration, and agitation speed, due to the enhanced stability of the polymer particles. However, once the parameter value was reached, the rate decreased due to the coagulation of the particles. Stable PTFE dispersion particles were obtained when the surfactant concentration was in the range between 3.48 × 10⁻³ and 32.48 × 10⁻³ mol/liter, which is below critical micelle concentration (CMC). The molecular weight of the PTFE obtained was a function of the surfactant and initiator concentrations, and the polymerization temperature. The molecular weight increased as each parameter decreased. This is against the phenomena observed in a conventional emulsion polymerization. A stable PTFE dispersion polymer having a high molecular weight was obtained by optimizing the reaction conditions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 777–793, 1999     

Preparation and full characterization of cationic latex of styrene-butyl acrylate

Cationic latexes based on styrene and butyl acrylate using cetyl trimethyl ammonium bromide (CTAB) as surfactant were carried out using both batch and semicontinuous emulsion polymerization. Monomer conversion, particle size and its distribution, ζ potential, latex surface tension were determined as function of CTAB levels. Evolutions of these properties were followed, and the results from batch compared to those from semicontinuous process. It was revealed that polymerization rate in batch process was enhanced with CTAB, and the polymerization rate was controlled by addition rate of the preemulsion in semicontinuous process. Molecular adsorption area of CTAB on latex particle surface was calculated, which showed clearly that ζ potential and surface tension in the latex were directly related with surfactant adsorption on the particle surface. The molecular surface adsorption area of CTAB on latex particle could be used to explain the evolution of latex properties such as ζ potential and latex surface tension.     

Synthesis of novel copper ion-selective material based on hierarchically imprinted cross-linked poly(acrylamide-co-ethylene glycol dimethacrylate)

A novel hierarchically imprinted cross-linked poly(acrylamide-co-ethylene glycol dimethacrylate) using a double-imprinting approach for the Cu²⁺ selective separation from aqueous medium was prepared. In the imprinting process, both Cu²⁺ ions and surfactant micelles (cetyltrimethylammonium bromide – CTAB) were employed as templates. The hierarchically imprinted organic polymer named (IIP-CTAB), single-imprinted (IIP-no CTAB) and non-imprinted (NIP-CTAB and NIP-no CTAB) polymers were characterized by SEM, FTIR, TG, elemental analysis and textural data from BET (Brunauer–Emmett–Teller) and BJH (Barrett–Joyner–Halenda). Compared to these materials, IIP-CTAB showed higher selectivity, specific surface area and adsorption capacity toward Cu²⁺ ions. Good selectivity for Cu²⁺ was obtained for the Cu²⁺/Cd²⁺, Cu²⁺/Zn²⁺ and Cu²⁺/Co²⁺ systems when IIP-CTAB was compared to the single-imprinted (IIP-no CTAB) and non double-imprinted polymer (NIP-CTAB), thereby confirming the improvement in the polymer selectivity due to double-imprinting effect. For adsorption kinetic data, the best fit was provided with the pseudo-second-order model for the four materials, thereby indicating the chemical nature of the Cu²⁺ adsorption process. Cu²⁺ adsorption under equilibrium was found to follow dual-site Langmuir–Freundlich model isotherm, thus suggesting the existence of adsorption sites with low and high binding energy on the adsorbent surface. From column experiments 600 adsorption–desorption cycles using 1.8 mol L⁻¹ HNO₃ as eluent confirmed the great recoverability of adsorbent. The synthesis approach here investigated has been found to be very attractive for the designing of organic ion imprinted polymer and can be expanded to the other polymers to improve performance of ion imprinted polymers in the field of solid phase extraction.     

About the possible upgrade of bentonite with respect to iodide retention capacity

Compacted bentonites are currently investigated as geotechnical barrier in high level radioactive waste (HLRW) repositories due to their low permeability, high swelling pressure, and cation adsorption capacity. In contrast, anions are repelled by the negatively charged smectite surfaces due to electrostatic forces. Therefore anion diffusion through bentonites is particularly slow (‘anion exclusion’). However, in case of crack formation bentonites do not possess anion retention capacity. In this case anions, neutral or negatively charged molecules or colloidal particles can pass the technical barrier faster. One of the hazardous anions is ¹²⁹I⁻ which is particularly dangerous due to its long half life, mobility, and biological relevance. In this context several studies concerning iodide adsorption by a variety of solids are available.The selection of an applicable bentonite additive for the improvement of iodide retention capacity of HLRW technical barriers is still subject to discussion. The optimum bentonite additive should possess high selectivity towards iodide, thermal stability, should not affect bentonite properties, and should be inexpensive.In this study we compare different potential iodide adsorbents using standardized conditions since it is well known that experimental parameters (concentration, time, precursor material, solid liquid ratio…) significantly influence the results of adsorption experiments. Therefore, only the application of standardized conditions allow for the direct comparison of a set of potential I⁻ adsorber materials.Obtained results indicate that organoclays (bentonites modified by organic surfactants) are supposed to represent the most suitable bentonite additive with respect to the upgrade of iodide retention capacity. Additionally, we could show that the addition of 5 wt.% hexadecylpyridinium treated bentonite did not affect the swelling pressure of compacted MX80 bentonite. However, long term tests and/or natural analogue studies have to be performed in order to be able to answer the open questions.     

Separation of Toluene and n‐Heptane through Emulsion Liquid Membranes Containing Ag+ as Carrier

Using silver ions as carrier in oil/water/oil‐type emulsion liquid membranes, batch wise extraction experiments were carried out to separate toluene from a mixture of toluene and n‐heptane. The separation performances, represented by the permeation rate, emulsion stability, and separation factor, were analyzed systematically by varying the operating parameters, viz., contact time, concentration of Ag⁺, emulsification time, surfactant concentration, membrane stabilizer concentration, relative amount of solvent, and initial feed phase concentration. The emulsion liquid membranes thus formed are stable, and Ag⁺ and surfactant concentrations strongly affect the permeation behavior of toluene.     

Surfactant concentration effects on the microemulsion polymerization of vinyl acetate

The polymerization of vinyl acetate in oil-in-water microemulsions stabilized with cetyltrimethylammonium bromide (CTAB) is reported here as a function of surfactant concentration. Reaction rate decreases as the CTAB/water ratio is increased in the parent microemulsions. Polymer particles in the latexes grow with conversion; they also become bigger as the initial surfactant content is increased. Number-average molar masses are smaller than those expected by termination by chain transfer to monomer, but weight-average molar masses increased as the surfactant concentration in the parent microemulsion is raised. However, the latter are much smaller than those obtained by polymerization in an emulsion stabilized with the same surfactant. Possible explanations to this unusual behavior are provided here.     

Pore size control in the synthesis of hydroxyapatite nanoparticles: The effect of pore expander content and the synthesis temperature

Porous hydroxyapatite particles were synthesized by a self-assembly method. The process was carried out under a basic pH condition using cetyltrimethylammonium bromide (CTAB) as cationic surfactant and 1-dodecanethiol (RSH) as micelle size expander. The focus of the present work was to investigate the effect of synthesis temperature and pore expander content on the dissociation degree of 1-dodecanethiol and the degree of swelling in the micelle structure. Swelling was related to the electrostatic interaction between the dissociated 1-dodecanethiol molecule (RS⁻) and the cationic molecules of CTAB (CTA⁺). The synthesized samples were characterized by low-angle X-ray diffraction (LA-XRD), N₂ adsorption–desorption experiments, X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). The results indicated that pore expander content as well as the synthesis temperature played a significant role in the swelling of the micelle structure. There was a decrease in particle length/diameter ratio with the increase in the synthesis temperature and pore expander concentration. Nanoparticles with pore size in range of 23–40 nm were obtained in this study.     

Two-resistance mass transfer models for the adsorption of dyestuffs from aqueous solutions using activated carbon

The adsorption of telon blue (acid blue 25) dye and deorlene yellow (basic yellow) dye on to carbon has been studied. A two-resistance mass transfer model has been developed based on film resistance and homogeneous solid phase diffusion. The model may be applied over a wider range of operating conditions than previous models since it has more extensive analytical components. The variables investigated were initial dye concentration and solid: liquid ratio, and the experimental and theoretical results were in good agreement. The adsorption of telon blue on to carbon has been described using an external mass transfer coefficient of 2.0 × 10⁻³ cm s⁻¹ and a homogeneous solid phase diffusion coefficient of 2.0 × 10⁻⁹ cm² s⁻¹. The adsorption of deorlene yellow has been described using an external mass transfer coefficient of 1.0 × 10⁻³ cm s⁻¹ and a homogeneous solid phase diffusion coefficient of 3.0 × 10⁻¹⁰ cm² s⁻¹.     

油基钻井液用腐殖酸类降滤失剂的研制与性能评价

使用有机胺对腐殖酸进行亲油改性,研制出一种适合油基钻井液用的腐殖酸类降滤失剂FLA180。室内性能评价表明,采用4%FLA180配制的密度为2.0 g/cm3油包水乳化钻井液在180℃高温下中压滤失量为0 mL、高温高压滤失量为9 mL;具有较强的抗钻屑和盐污染能力;同时该降滤失剂具有降粘作用,有利于提高机械钻速,适用于高温高压深井。通过性能比较,该降滤失剂降滤失性能优于国内主要应用的油基降滤失剂性能。     

Surfactant-assisted synthesis and catalytic activity for SOx abatement of high-surface-area CuMgAlCe mixed oxides

CuMgAlCe mixed oxides were prepared by a modified coprecipitation–calcination method using CTAB as surfactant template. All the precursors showed hydrotalcite-like layered structure and mixed oxides with mainly periclase phase were obtained after calcination. Catalytic activity for SO₂ removal of mixed oxides was examined through adsorption–reduction cycles under the conditions similar to those of FCC units. The results showed that incorporation of both Ce and Cu could improve SO_x oxidative chemisorption. CTAB/metal molar ratio during synthesis had a significant influence on the structural properties of mixed oxides. Sample CuMgAlCe-0.1 prepared by CTAB/metal molar ratio of 0.1 had the highest specific area 142.2 m²/g and also presented the best SO₂ adsorption rate and capacity. This behavior is mainly due to its exposed more adsorption sites provided by high specific surface area, facilitating SO₂ diffusion and contact with active components. It still possessed excellent cyclic stability that is beneficial for industrial application.     

Salt-Induced Constructions of Gemini-like Surfactants at the Interface and Their Effects on the Interfacial Tension of a Water/Model Oil System

It is an urgent issue to enhance oil recovery for unconventional reservoirs with high salinity. Focused on this topic, salt addition is a powerful tool to motivate the surfactant assembly at the water/oil interface and improve the interfacial activity. We used a cationic surfactant cetyltrimethylammonium bromide (CTAB) and an anionic salt dicarboxylic acid sodium (CnDNa) to construct gemini-like surfactants at the interface and evaluated their ability to reduce the interfacial tension (IFT) between model oil (toluene and n-decane, v:v = 1:1) and water. Interestingly, the fabrication of a (CTAB)₂/C4DNa gemini-like surfactant was hardly achieved at the fresh water/model oil interface, but accomplished at the brine/model oil interface. At a high NaCl concentration (100,000 mg L⁻¹), the IFT value is reduced to 10⁻³ mN m⁻¹ order of magnitude, which is generally desired in practical applications. The control experiments displacing the surfactant type and the spacer length further confirmed the NaCl effects on the interfacial assembly.     

The influence of cationic surfactant CTAB on optical,dielectric and magnetic properties of cobalt ferrite nanoparticles

In the present work, the influence of cationic surfactant CTAB (cetyltrimethylammonium bromide) on size, shape and coalescence behaviour of cobalt ferrite nanoparticles (CFNPs) synthesized via hydrothermal method is reported. Pure CFNPs show no additional peaks, whereas α-Fe₂O₃ phase is observed in CTAB added CFNPs upon annealing. FT-IR analysis confirms the formation of M − O vibrational bands (metal -oxygen) at tetrahedral A-site and octahedral B-site for both samples. SEM observations reveal less agglomeration and smaller particle size for surfactant added CFNPs. Raman spectral study confirms the formation of cubic spinel structure and Raman active modes of CTAB added CFNPs. UV–Vis spectra indicate a decrease in the energy band gap with annealing. The dielectric constant of surfactant added CFNPs decreases with increasing applied frequencies for both real and imaginary, but ac conductivity increases with increasing frequencies. Two sextet patterns of Fe³⁺ trivalent ions from tetrahedral and octahedral sites are observed in Mössbauer spectra. VSM study indicate the ferrimagnetic nature of CTAB added CFNPs. The electrochemical analysis reveals the pseudocapacitive nature of working electrode prepared by CTAB added CFNPs.     

表面活性剂对煤岩润湿性的影响实验研究

在煤层气储层钻井过程中,钻井液浸泡并一定程度地侵入煤岩,钻井液中的各种添加剂与煤岩表面接触,容易使煤岩表面性质发生变化,影响煤层气的解析和渗流,从而影响煤层气产能。因此,开展表面活性剂对煤岩润湿性的影响研究具有重要的实际意义。通过实验研究了不同表面活性剂种类对煤岩润湿性的影响,加入阴离子表面活性剂后,煤岩表面亲水性增强,加入阳离子表面活性剂后,煤岩表面亲水性减弱。该研究揭示了表面活性剂对煤岩润湿性的影响规律,为钻井液体系优选与钻井液性能调配提供了技术指导,有助于保护储层并提高煤层气产能。     

Preparing ceramic membranes for oil-in-water emulsions separation with oil-based drilling cutting pyrolysis residues (ODPRs) as raw material

Oil-based drilling cutting pyrolysis residues (ODPRs) are one of the solid wastes from pyrolysis of the oil-based drilling cuttings (OBDCs) that need to be recycled as raw materials to avoid the possible pollution. In this study, a facile low-cost ceramic membrane for oil-in-water emulsions separation was prepared with ODPRs incorporating with fly ash as raw material. CaCO₃ in ODPRs would decompose acting as pore-forming agent, and anorthite was formed in resultant membranes. The obtained membrane with 30 wt% ODPRs and 70 wt% fly ash fired at 1050 °C possessed apparent porosity of 38.2%, mean pore size of 0.4 μm, flexural strength of 13.1 MPa, and Darcy permeability of 1.06 × 10⁻¹³ m². Consequently, commendable filtration performance for oil-in-water emulsions was presented. In addition, the ceramic membrane showed favorable recyclability and corrosion resistance. Leaching test indicated that the membrane is safe for oil-in-water emulsion separation. Hereby, this paper confirmed the availability of ODPRs for preparing ceramic filtration membranes, and provided a new environmental conservation way to treat oil-in-water emulsions that was consistent with the sustainable development goals.