Search

The dilational rheological properties of aqueous solutions of anionic surfactant petroleum sulfonate (KPS), zwitterionic surfactant alkyl sulfobetaine (ASB) and their mixtures have been investigate...

Considering the significant importance of emulsification for heavy oil recovery, a good‐emulsification‐oriented (GEO) (rather than the conventional ultralow interfacial tension (IFT) oriented) surfactant‐polymer (SP) system was employed to remove heavy oil. Specifically, the emulsification behavior and viscosity‐reduction property of heavy oil in porous media were first studied by flood tests. Then, such a GEO SP was used to displace heavy oil for recovery measurement. It is found that first, as migration increases in porous media, the in situ emulsified oil droplets evolve into smaller and more uniform droplets (without coalescence), thus, exhibit self‐adjustment ability to match with, and plug, the pores. An increase in surfactant content and seepage velocity also makes the emulsion's particles smaller and more uniformly distributed. Second, such oil‐in‐water emulsification indeed helps to reduce heavy oil viscosity in porous media and there is an optimal surfactant content for such viscosity reduction: The lower the water cut, the greater the optimal surfactant content, the worse the viscosity‐reduction effect. Third, on its own, the GEO surfactant performs very poorly in recovering heavy oil and is even worse than the single polymer; therefore, such a surfactant should be jointly used with a polymer in an SP system instead of on its own, but an excessive surfactant content in the SP seems to hinder the recovery, while the large slug size tends to contribute significantly to an improved oil recovery.

In the present work, the interfacial dilational properties of hydrophobically modified polyacrylamide (HMPAM) at the kerosene/water interface were investigated by means of drop shape analysis metho...

An original device was developed by our research group and used for quantitatively and qualitatively studying the stability mechanism of two liquid droplets in another liquid phase. The squeeze time can be employed to detect the stability of liquid droplets. The effect of water soluble emulsifier TX-100 and oil soluble one Span-80 on the squeeze times of both aqueous and kerosene droplets have been investigated. Moreover, the influences of three polyether demulsifiers with different structures, linear PEL, branched PEB and star-type PES, on the stability of liquid droplets have also been studied. Based on experimental results, the hydrophilic head group ethoxylation (EO) chain of TX-100 nearly flats at interface and forms compact interfacial film closed to water phase, which makes kerosene droplets stable at aqueous. On the other hand, two water droplets contain TX-100 will coalesce at once when they contact each other. For oil soluble emulsifier Span-80, the compactness of two sides of interfacial film leads to both stable water droplets and oil droplets. The molecular size of demulsifier may play the crucial role in controlling droplets coalescence: PEL with smaller size can easily destroy aqueous droplets in oil; PEB shows strong effects on both kerosene and aqueous droplets for it has a moderate molecular size; PES with larger size shows strong ability to destroy oil droplets in aqueous but little effects on aqueous droplets in oil.

Self-emulsifying flooding technique is an efficient enhanced oil recovery technology for low permeability reservoirs, which can expand the sweep efficiency and improve the formation heterogeneity. But some problems, such as large dosage of surfactant and emulsion instability, limit the extensive application of the technology. In view of the above problem, the modified Al2O3 nanoparticle emulsion interface enhancer was developed in this paper. The emulsion stabilized by surfactant and Al2O3 nanoparticles with different wettability was studied through bottle test and Turbiscan Lab, and the emulsion viscosity was tested by the rheometer. The optimal formula of the enhanced self-emulsification system was selected by comparing the instability kinetic index TSI and the emulsification viscosity increasing rate. The results show that the strong water-wet α-Al2O3 nanoparticles are more likely to produce flocculation and sedimentation in the emulsion surfactant solution, which is not conducive to stabilize emulsion, while γ-Al2O3 nanoparticle with wetting angle of 103° shows good performance of stabilizing emulsion with surfactant; When 0.4% self-emulsifying surfactant is mixed with 0.5% hydrophobic γ-Al2O3 nanoparticles, the stability of formation emulsion is the best. At the same time, the emulsification viscosity is 18.5 mPa s, which can be contributed to the good oil-water interface adsorption property of Al2O3 nanoparticles. Al2O3 nanoparticles can adsorb in the surface of the emulsion droplets, which can improve the interfacial film strength and the bulk phase viscosity.

The dilational rheology of two different types of polyether demulsifiers solutions, linear propylene glycol polyether and branched glycerol polyether, at the water-crude oil interface have been investigated by dilational rheological measurements. This paper research that except the concentration of 10 ppm, linear propylene glycol polyether appears higher moduli than those of branched polyether because branched one has shorter chain at the same molecular weight, which will result in the faster diffusion. However, at optimized concentration, the modulus of branched one is higher than that of linear one, which can be attributed to the stronger interactions between branched chains at interface. The linear demulsifier propylene glycol polyether shows stronger ability of reducing modulus for diluted crude oil with higher viscosity. On the contrary, branched demulsifier glycerol polyether acts well when concentrations of diluted crude oils are lower. The reason is that linear demulsifier has the stronger ability of adsorption and branched one shows the stronger ability of replacement of natural active fractions.

The dynamic interfacial tensions (IFTs) of three different types of surfactant solutions, cationic surfactant hexadecyl trimethylammonium (CTAB), anionic surfactant sodium dodecyl benzenesulfonate (SDBS), and non-ionic surfactant Triton X-100 (TX-100), against model oil containing oleic acid (OA) have been investigated by a spinning drop interfacial tensiometer. The influences of the OA concentration and addition of alkali have been studied. The experimental results show that OA added to the oil phase has a significant effect on interfacial behaviors of surfactant solutions. An obvious synergistic effect on reducing IFT can be observed for low-concentration cationic surfactant CTAB solution because the tight mixed adsorption films will be formed through electrostatic attraction between CTAB and OA molecules. However, the synergistic effect will disappear at a high surfactant concentration by the formation of mixed micelles. For the anionic surfactant SDBS system, the mixed adsorption of SDBS and OA molecu...

In this research, the heavy oil emulsifying and viscosity reducing properties of a series polyethers have been studied by the emulsion stability analysis and viscosity measurements. The experimental results show that the polyethers (with molecular weights of 8400, 12,600 and 14,600) are efficient surfactants for heavy oil emulsification and viscosity reduction. To illustrate the mechanisms, we carried out the study of interfacial properties by interfacial tension and dilational rheology measurements. The experimental results show that the resins and asphaltenes in heavy oil have strong interfacial activity. The adsorption of active components will form interfacial film with certain intensity, which may help to form stable W/O emulsion. On the other hand, the adsorption of polyethers will reduce interfacial tension and form sub-layer construction at higher concentration, which leads to the formation of elastic interfacial layer with a certain strength. For the mixed systems of active components with polyethers, the mixed interfacial layers show almost the same properties just as polyethers used alone, demonstrating that the interfacial layers will be occupied mainly by polyether molecules. The water-soluble polyether with suitable molecular structure will form strong interfacial film, which may be helpful for forming stable O/W emulsion and reducing viscosity of heavy oil obviously.

Various experimental methods were used to investigate interaction between polymer and anionic/nonionic surfactants and mechanisms of enhanced oil recovery by anionic/nonionic surfactants in the pre...

The transformation of cyclodextrins (CDs) and alkanes from separated monomers to inclusion complexes at the interface is illustrated by analyzing the evolution of interfacial tension along with the variation of interfacial area for an oscillating drop. Amphiphilic intermediates are formed by threading one CD molecule on one alkane molecule at the oil/aqueous interface. After that, the amphiphilic intermediates transform into non-amphiphilic supramolecules which further assemble through hydrogen bonding at the oil/aqueous interface to generate a rigid network. With the accumulation of supramolecules at the interface, microcrystals are formed at the interface. The supramolecules of dodecane@2α-CD grow into microrods which form an unconsolidated shell and gradually cover the drop. However, the microcrystals of dodecane@2β-CD are significantly smaller which fabricate into skin-like films at the interface. The amphiphilic intermediates during the transformation increase the feasibility of self-emulsification and the skin-like films enhance the stability of the emulsion. With these unique properties, CDs can be promising for application in hydrophobic drug delivery, food industry and enhanced oil recovery.

The host–guest interaction was successfully used in the construction of supramolecular recognition system, with β-cyclodextrinpolymer-66βCD2su as the host polymer and hydrophobically modified polyacrylamide (AP-C18), which contains a small quantity of hydrophobic octadecyl radical groups, as the guest. By adding 66βCD2su to AP-C18 solution, the viscosity can be greatly increased, due to the formation of inclusion association structure of the polymer; at this time, the concentration of the solution is lower than the critical association concentration. Association effect-stabilized O/W crude oil emulsion was prepared, and its stability was discussed by the Turbiscan Lab Expert stability analyzer. The results indicated that the stability of mixture emulsion was significantly enhanced, which is in contrast to the emulsion stabilized by the single amphiphilic polymer. In this paper, interactions between β-CD dimers and AP-C18 are elaborated, and the enhanced oil emulsification mechanism is further explored.

Hydrophobically modified polyacrylamidepolymers were synthesized by an aqueous micellar copolymerization, the N -benzyl- N - n -hexadecyl acrylamide being used as hydrophobic comonomer. The effect of the molecular weight (MW) and surfactant interactions on the rheological properties and oil-water interfacial activity were studied. The results indicate that increasing MW, the critical aggregation concentration of amphiphilic polymer will be decreased, and the network structural strength increased, which was measured by fluorescent probes, DLS and electron microscope. Mixing with the surfactant, sodium dodecyl sulfate (SDS), the solution viscosity increased at first and decreased later on with increasing the ratio of SDS concentration, and the dynamic interfacial tension between oil and water can be reduced by two orders of magnitude compared to the polymer solution only. The result of enhance oil recovery performance of the polymer/surfactant compound system is that it can significantly reduce the residual oil saturation due to the synergistic effect of the increasing viscosity and surface activity. The overall recovery efficiency was raised by 10–25% OOIP compared to the baseline polymers.

The adsorption behaviors of dodecyl trimethyl ammonium bromide (C12TAB) and the catanionic mixtures of C12TAB with sodium dodecyl sulfate (SDS), sodium dodecyl sulfonate (SDDS) and sodium dodecanoate (DAS) on quartz surface have been investigated. Physicochemical parameters such as the critical micelle concentration (CMC), surface tension, contact angle, adhesional tension and work of adhesion have been estimated. At the interface of quartz and aqueous solution of catanionic mixture, there is a competition between anionic surfactants and quartz surface in attracting cationic surfactants. SDDS and DAS fail to inhibit the adsorption of C12TAB because of the smaller size and less negative charge of the head-groups, even the amount of anionic surfactants well surpasses that of C12TAB. Instead the anionic surfactants are dragged by cationic surfactants to quartz surface and form a mixed monolayer on the quartz surface. The insert of anionic surfactants reduces the repulsion between the cationic molecules and results in closer packing of molecules in adsorption layers. Thus, SDDS-C12TAB and DAS-C12TAB have displayed stronger hydrophobic modification at quartz surface than pure C12TAB. However, the electrostatic attraction between excessive SDS and C12TAB is strong enough to constrain C12TAB and decreases the adsorption on quartz surface. Only a small amount of catanionic complexes with the structure like zwitterionic surfactant adsorb on quartz through the interaction between the positive sites of surfactant complexes and negative sites of quartz. Over CMC, bilayers are formed on quartz surface in the systems of SDDS-C12TAB and DAS-C12TAB, while micelle structures are adsorbed on quartz surface for SDS-C12TAB.

The dynamic interfacial dilational properties of anionic Gemini surfactants (oligooxa)-α,ω-bis( m -octylbenzene sulfonate) (C 8 E 4 C 8 and C 8 E 8 C 8 ) with polyoxyethylene spacers at the water–air interface were investigated by means of oscillating the drop profile method. The influences of temperature and salt on dilational properties were explored. The experimental results show that the special structure of surfactant C 8 E 8 C 8 is a principal factor to control the nature of interfacial adsorption film. The distinct two peak values appear in dilational modulus vs. time curves for surfactant C 8 E 8 C 8 , which is different from that of traditional surfactants with low molecular weight. The first peak is believed to be related to the molecular diffusion-exchange process between the bulk and interface, and the second peak may be due to the formation and collapse of interfacial sublayer by ethylene oxide groups. In addition, the temperature has obviously effect on the second peak value of dilatioanl modulus. However, there is nearly no effect on the value of the second peak by addition of NaCl. The mechanisms responsible for unique interfacial behaviors mentioned above have been provided schematically.

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.

The interfacial interactions between organic acid and betaine molecules play an important role in reducing interfacial tension (IFT). To deeply detect the arrangements of organic acid and betaine molecules at the interface, the dilational rheological properties of mixed adsorption films formed by oleic acid and octadecyl carboxyl betaine (18PC) or octadecyl sulfobetaine (18PS) were investigated using drop shape analysis method at the decane-water interface. The influences of aging time, oscillation frequency and surfactants concentration were detected. The experimental results show that the properties of 18PC and 18PS adsorption film are controlled by both the fast diffusion-exchange process between the bulk and the interface and the slow re-arrangement process in the interface. 18PC film is tighter than that of 18PS because the size of carboxyl is small than sulfonyl. Oleic acid and betaine surfactants can form mixed adsorption films with less strength caused by the rapid transfer of oleic acid between the bulk and the interface, but more elastic due to the enhancement of the intermolecular interaction. In this case, the oleic acid molecules are easier to insert into the spaces between 18PS molecules on the interface, which results in a more tight mixed film than oleic acid/18PC film.

In this article, we have investigated interfacial tensions (IFTs) of anionic-nonionic surfactant fatty alcohol polyoxyethanol carboxylate (CnEOmC) and their mixed solutions against n-alkanes, crude oil and model oils containing crude oil fractions, such as saturates, aromatics, resins and asphaltenes. The experimental results show that EO group plays a crucial role in reducing IFT by adjusting the area occupied for CnEOmC molecules at the interface and only surfactant with optimum EO number produces lower IFTs against n-decane, named size compatibility. The hydrophilic-lipophilic balance is another important factor for reducing IFT. Ultralow IFT value can only be achieved when both hydrophilic-lipophilic balance and size compatibility are met simultaneously. Fortunately, one can adjust the hydrophilic-lipophilic balance and keep size compatibility simultaneously by mixing CnEOmC with different EO numbers to produce ultralow IFTs for both hydrocarbons and crude oil. Moreover, the spaces with different sizes occur at the mixed adsorption film. As a result, we can observe synergism between model oils containing resins, aromatics or asphaltenes during wide concentrations and mixed solution of C14EO3C and C14EO7C with mass fraction ratio of 1:1. This may be another reason for the ultralow IFT values of mixed solutions against crude oil. The mechanism provided in this paper is very important for the design of chemical flooding at high salt reservoir conditions.

Betaines and anionic-nonionic surfactants are suitable for applying in enhanced oil recovery (EOR) in the high-temperature and high-salinity reservoir conditions. We have used the spinning drop method to investigate the interfacial tension (IFT) values of alkyl carboxylicbetaine (ACB) and five types of anionic-nonionic surfactant (C14E3C, C16E3C, C18E3C, C18E5C and C18E10C) with different ethylene oxide (EO) numbers and different alkyl chain lengths against hydrocarbons and crude oil. Thereafter, under the same conditions, the IFT values of ACB and anionic-nonionic surfactant mixed solutions have also been investigated. The experimental results exhibit that for achieving ultralow IFT the proper hydrophilic-lipophilic balance (HLB) is prerequisite, but the tightness of the adsorption film is the key factor, which is controlled by the consistency of the spaces occupied at the oil side and the water side of an interface. This mechanism is so called “size compatibility”. The ultralow level IFTs have been reached during wider concentration ranges as the mixed systems against crude oil, which have not happened when the hydrocarbons are the oil phase. These phenomena demonstrate the strong synergistic effect among ACB, anionic-nonionic surfactant and natural surface-active materials, which is important for the development of high-temperature and high-salinity oil reservoirs.

The fly ash particle was modified with various surface coupling densities and IR testified that γ-glycidoxy propyl trimethoxy silane (GPMS) is located on the surface of it Vis chemical bond. The surface GPMS-coupling density could influence the hydrophilic–lipophilic properties of the particles. The contact angles increase with the increase of additive amounts of modifiers. It indicates the surface of fly ash changed from water wetting to oil gradually. Using DLS, the dispersion state of fly ash with different GPMS-coupling densities was studied. A suitable modification of fly ash with GPMS did not change the dispersion state significantly. To achieve good dispersibility in HPAM solution, the surface GPMS-coupling density should be controlled within the range of 1.4–3 μmol (m2 FA)−1. Using fly ash particle–surfactant–polymer system, the O/W emulsion stabilized is investigated to stable Pickering emulsion. The particle in surfactant and polymer solution synergistically interacted at the oil/water interface. The emulsion system of GPMS (2.98)-FA particles in PAM and SDS solution shows higher thermal stability as compared to other particles as it was dispersed very well on the emulsion interface.

Different measurements were conducted to study the mechanisms of enhanced oil recovery (EOR) by surfactant-induced wettability alteration. The adhesion work could be reduced by the surfactant-induced wettability alteration from oil-wet conditions to water-wet conditions. Surfactant-induced wettability alteration has a great effect on the relative permeabilities of oil and water. The relative permeability of the oil phase increases with the increase of the water-wetness of the solid surface. Seepage laws of oil and water are greatly affected by surfactant-induced wettability alteration. Water flows forward along the pore wall in the water-wet rocks and moves forward along the center of the pores in the oil-wet rocks during the surfactant flooding. For the intermediate-wet system, water uniformly moves forward and the contact angle between the oil–water interface and the pore surface is close to 90°. The direction of capillary force is consistent with the direction of water flooding for the water-wet surfac...

The dilational properties of a branch-shaped polyether-type nonionic demulsifier (PEB), a comb-shaped polyether-type nonionic demulsifier (PEC), and a star-shaped polyether-type nonionic demulsifier (PES) at the decane–water interfaces were investigated by Langmuir trough method through oscillating barrier and interfacial tension relaxation methods, which are mainly in the influences of oscillating frequency and bulk concentration on dilational properties. Meanwhile, the effect of demulsifiers on interfacial dilational modulus of diluted crude oil was also explored. The experimental results indicate that all demulsifiers can decrease the dilational modulus of diluted crude oil at the experimental concentration. The addition of PEB causes the dilational modulus of crude oil to be lower than that at the water–decane interface. The demulsifier PEC has a similar effect with PES to influence the interfacial film of crude oil: at low concentration, the dilational modulus of mixed interfacial film is lower than ...

The effects of acidic components and asphaltenes on the dilational rheological properties of hydrophobically modified polyacrylamide (APP5) have been measured as a function of the time, frequency, bulk concentration, and interfacial pressure by means of a drop shape analysis method. It is established that acidic components and asphaltenes play an important role on the interfacial properties of the APP5/crude oil component mixture at water–kerosene interface. With the addition of acidic components, the dilational modulus of the mixture not only increases with time but is also higher at low concentrations and runs through a maximum at a lower concentration compared to pure APP5. Also, the phase angle of APP5/acidic components is lower compared to pure APP5. The results indicate that the appearance of more elastic films because of the mixed adsorption of acidic components and APP5 molecules. The addition of asphaltenes does not influence the interfacial properties of APP5 at high APP5 concentrations. However...

The dynamic interfacial tensions (IFT) of four p -( n -lauryl)-benzyl polyoxyethylene ether carboxybetaine C 12 BE x CB ( x =0, 1, 2, 3) have been investigated by a spinning drop interfacial tensiometer. The influence factors such as ethylene oxide group, surfactant concentration, organic base, electrolyte concentration and type are explored between C 12 BE x CB solutions and two oils including n -alkane model oil and Shengli crude oil. It is found that the n min (the minimum alkane carbon number) and IFT min increase with increase in the ethylene oxide group for n -alkane model oil systems. For Shengli crude oil, the C 12 BE x CB surfactants used alone cannot reduce the IFT to ultralow value. In order to meet the demand, the organic base, monoethanolamine (MEA), is applied together with C 12 BE x CB to form organic base/surfactant system. The results show that there exists a synergistic effect between organic alkaline MEA and C 12 BE x CB surfactant. At optimum MEA concentration (0.10 wt%) and optimum ethylene oxide group number ( x =0, 1), the IFT value becomes lower than 10 −2 mN/m. All these results show that the interfacial surfactant concentration and the surfactant molecular size are two most important factors in dominating ultralow IFT. Moreover, it is found that electrolyte concentration and type have little effects on IFT and the C 12 BE x CB surfactants exhibit good salinity resistance.

The dilational rheological behaviors of absorbed films of p-(n-alkyl)-benzyl polyoxyethylene ether carboxybetaine CxBE2CB (x = 8, 10, 12) at the water–decane interface have been investigated by the drop-shape analysis method. The influences of time, oscillation frequency, and bulk concentration on dilational modulus and phase angle have been expounded. The experimental results show that the phase angle of CxBE2CB (x = 10, 12) decreases with the increase of time, the slope of the log ϵ − log ω curve and phase angle of CxBE2CB (x = 10, 12) decrease in a wide concentration range. These phenomena become more and more apparent with the increase of hydrocarbon chain length and it cannot be attributed to the diffusion-exchange process between the bulk and the interface. It is reasonable to consider that ethylene oxide groups are flexible and can be compressed and expanded, just like a spring. Therefore, the compression and expansion of the ethylene oxide groups in the interfacial layer and the exchange between i...

In order to study the interfacial activity of the anionic-nonionic surfactant, five nonyl phenol polyoxyethylene ether carboxylates were synthesized and mass spectra were used to characterize their structures. The tensions of the anionic–nonionic surfactant aqueous solutions against crude oil were measured and the effects of the surfactant structure, concentration, and salinity on the interfacial activities were discussed. It was shown that nonyl phenol polyoxyethylene (6) ether carboxylate can produce ultralow interfacial tension when the concentrations are not lower than 0.10%, exhibiting a high interfacial activity and a good anti-dilution resistance. Moreover, it was proved that there exists synergism between NaCl and MgCl2 (or CaCl2), which is crucial to achieve the ultralow interfacial tension.

The interfacial dilational rheological behaviors of four zwitterionic surfactants with benzene ring and polyoxyethylene group, p-(n-lauryl)-benzyl polyoxyethylene ether carboxybetaine C12BExCB (x = 0, 1, 2, 3), were investigated via the drop shape analysis method. The influences of time, oscillating frequency and bulk concentration on dilational properties were explored. The experimental results show that the number of ethylene oxide groups is one of the principal factors to control the interfacial film. The dilational properties of C12BExCB are quite different from those of common surfactants: the phase angle decreases with aging time, the slope of the loge − logω curve and phase angle of C12BExCB decrease in a wide concentration range, and the dilational modulus of C12BExCB passes through a plateau value with the increasing concentration for surfactant with more ethylene oxide groups. These phenomena become more and more apparent with increasing ethylene oxide groups and it cannot be attributed to the diffusion-exchange process between the bulk and the interface. It is reasonable to consider that ethylene oxide groups are flexible and can be compressed and expanded, just like a spring. The compression and expansion of the ethylene oxide groups in the interfacial layer and the exchange between interface and sub-layer play a crucial role for C12BExCB. Possible schematic diagrams of adsorbed molecules with time and concentration at the water–decane interface are proposed. The results of static modulus measurements and dynamic interfacial viscoelasticity for CyBE2CB (y = 8, 10, 12) with different length of hydrophobic chain can support our provided mechanism strongly.

Advancing contact angle ( θ ), for aqueous solutions of the zwitterionic surfactants, hexadecanol glycidyl ether glycine Betaine (C 16 PB), guerbet alcohol hexadecyl glycidyl ether glycine Betaine (C 16 GPB), hexadecanol polyoxyethylene(3) glycidyl ether glycine Betaine (C 16 (EO) 3 PB) and guerbet alcohol hexadecyl polyoxyethylene(3) glycidyl ether glycine Betaine (C 16 G(EO) 3 PB), were measured on the quartz surface by the sessile drop analysis. The atomic force microscope (AFM) has been used to detect the nature of adsorption film at quartz surface. The obtained results indicate there are only slightly changes of contact angle as a function of bulk concentration for four surfactants during the experimental concentration range caused by the random arrangement of surfactant molecules at quartz surface through Lifshitz–van der Waals interactions. For C 16 PB and C 16 GPB, a similar adsorption density at water–air and quartz–water interface is observed. In the case of C 16 (EO) 3 PB and C 16 G(EO) 3 PB solutions, a smaller surfactants adsorption at quartz–water interface than at water–air interface probably results from steric effect due to parallel orientation of surfactants in the monolayer at quartz–water interface resulted from the interaction between EO group and quartz. The adsorption characteristics of zwitterionic surfactants remain less variation with the insertion of EO group and the presences of branched-chain in the hydrophobic group are quite opposite. For C 16 PB and C 16 (EO) 3 PB, a three-stage adsorption mechanism has been provided, while a four-stage mechanism must be taken into account for C 16 G PB and C 16 G(EO) 3 PB. The characteristics of force curves measured by AFM between alkyl-modification tips and surfactant-modification quartz plates can strongly confirm the nature of modified film on quartz surface and ensure the adsorption mechanism provided above.

Alkyl ether carboxylate is one type of surfactant that can produce ultralow interfacial tension (IFT) under high-salinity and high-temperature conditions. In this paper, the influence of counterion...

The dynamic interfacial tensions between offshore crude oil and different types of EOR surfactants were investigated by spinning drop method at 65 degree under the condition of weak base (pH ∼ 8) in the present work. Effects of surfactant concentration on the dynamic interfacial tension were investigated. In the presence of weak alkali, the active components of crude oil can react at the interface to produce surface-active species in situ. The interactions among the added surfactants, the petroleum active components and in situ produced surface-active species together determine the dynamic interfacial tension behaviors, whose curves show “L”, “V,” and “W” shapes, respectively. Surfactant type and concentration play the crucial roles on dynamic interfacial tension behaviors.

The dilational properties of adsorbed film of three branched-alkyl benzene sulfonates at the air–water interface have been investigated by drop shape analysis method. The influences of time, dilational frequency and bulk concentration on surface dilational elasticity and dilational viscous component were expounded. The experimental results show that the change of surface dilational properties with time is accordant to the variation of surface tension with surface aging. At low concentration, the dilational properties are independent of frequency and the film behaves elastic in nature. As concentration increases, the surface film shows remarkable viscoelasticity, which means the diffusion-exchange process controls the dilational properties. Moreover, the position of the phenyl in the alkyl chains is one of the principal factors to control the nature of interfacial film: as the phenyl is moved from a terminal position to a more central position, the dilational elasticity increases. The surface elasticity was compared with the stability of lamella stability made with these surfactants. The results suggest that surface dilational elasticity is crucial for the ability of a surfactant solution to form a stable lamella.

Hydrophobically associating polyacrylamide (HAPAM) is considered as a promising candidate of polymer flooding because of its excellent apparent viscosifying capability. However, the effective viscosity and the oil displacement efficiency of HAPAM are lower than those of conventional polymers at a concentration of 2000 mg/l. Therefore, the microstructures of two types of polymers were investigated by scanning electron microscopy (SEM) to reveal the relationship between the morphology and properties. The specimens were prepared by accelerated freeze-drying in order to keep polymers with their original morphology without distortion. In aqueous solution, associative polymer exhibited a compact three-dimensional network structure, while only loose network structure was found in conventional polymer. A number of filaments are attached to the associative polymer skeletons when the polymer concentration is higher than the critical association concentration ( CAC ). But in the porous media, most of the networks of conventional polymer were larger and more integrated than those of associative polymer. It may be interpreted by absorption loss of HAPAM and spatial confinement in porous medium.

Polymer flooding has been an important process to enhance oil recovery (EOR) worldwide. In practice, partially hydrolyzed polyacrylamides (HPAMs) have many defects including shear degradation and sensitivity to salt. For these reasons, hydrophobically associating polyacrylamides (HAPAMs) have been developed for harsh oil reservoirs. In this work, the properties of two classes of polymers (HPAMs and HAPAMs), including apparent viscosities, effective viscosities in porous media, and oil-displacement efficiencies, are studied. As expected, HAPAM exhibits apparent viscosity enhancement properties due to intermolecular hydrophobic association while HPAM cannot. However, the effective viscosity of HAPAM is always lower than HPAM possibly because of adsorption loss and the reduction in strength of the hydrophobic association through porous media. The tertiary oil recovery increases with the increment of the effective viscosity of polymer. Oil-displacement efficiency of HAPAM is also lower than HPAM at t...

Synergism between alkylbenzene sulfonate and nonionic surfactant was studied by measuring interfacial tensions of surfactants and their mixtures against a homologous series of alkanes. Four di-n-alkylbenzene sulfonate homologues and a nonionic surfactant, lauryl alcohol polyoxyethylene(9) ether, were used. Effects of hydrophilic-lipophilic ability of surfactant, mixing ratio, and salinity of aqueous phase on synergism were investigated. It is found that the synergism for producing low interfacial tensions derives from the change of the hydrophilic-lipophilic abilities of the surfactant systems from the individual surfactants to their mixtures, which is confirmed by analyzing the alkane scanning curves, and the method to achieve synergism is adding the hydrophilic nonionic surfactant to the lipophilic alkylbenzene sulfonate, and ultralow interfacial tensions (

The dynamic dilational properties of sodium 2-(2-(alkylaryloxy)-alkylamido)ethanesulfonates (12+nB-Ts) at the air–water interfaces were investigated by drop shape analysis, and their foam properties were also measured. The influences of time and bulk concentration on surface dilational properties were expounded. The results show that the molecular interaction controls the nature of adsorption film during lower concentration range, and the film behaves elastic in nature. During higher concentration range, the diffusion exchange process controls the dynamic dilational properties and the surface film shows remarkable viscoelasticity. An increase in hydrophobic chain length enhances the molecular interaction at low concentration and speeds up the diffusion exchange process at high concentration, which results in the different variations of modulus at different concentration regions. For 12+nB-Ts, too short a chain probably produces bad film elasticity, whereas too great a length produces too fast liquid drainage. Therefore the optimal length in the branched chain leads to the best foam stability.

A series of novel surfactants, sodium N-2-(alkylphenoxy)-tetradecanolytaurinates (12 + nB-T, where 12 means the carbon number of alkyl chain in the main chain and n is the carbon number of alkyl chains in the side chain attached to the phenoxyl group, n = 0, 2, 6) bearing identical polar groups, were designed and synthesized. The dilational properties of the three surfactants at the water–air and water–decane interfaces were investigated by drop shape analysis. The influences of oscillating frequency and bulk concentration on dilational properties were explored, and the effect of alkyl chain length in the side chain on interfacial behavior has been expounded. The longer alkyl chains in the side chains lead to a higher surface dilational elasticity at low bulk concentrations, owing to strong interaction among the longer hydrophobic alkyl chains. However, at high bulk concentrations, the longer the hydrophobic alkyl chain is, the easier the diffusion-exchange between the bulk and the surface becomes. As a r...

Model surfaces with controllable wettability gradient are made by adjusting the feed mole ratio of 11-mercapto-1-undecanol and 1-octadecanethiol to form mixed self-assembled monolayers on gold. The surface adhesion spectra were obtained by force volume analysis at nanometer scale with atomic force microscopy and direct force measurement of droplets on surfaces with a microbalance. The results from direct measurement of liquid droplet-substrate adhesion are in good agreement with the measurements of force volume statistics and contact angle. It can thus be a useful supplement approach to understand surface wetting and adhesion property.

We demonstrate here that surface wetting transitions and contact angle hysteresis can be significantly altered by manipulating the droplet–surface interaction, which has never been reported before. The dynamic wetting behavior of a pressed water droplet on responsive polymer brushes-modified anodized alumina with pre-modified dilute initiator is shown. The wetting transition between superhydrophobicity and hydrophilicity can or cannot be achieved depending on the responsiveness between droplets of different pH, the concentrations of electrolytes and the environmental temperature and surface grafted stimuli-responsive polymer brushes. The contact angle changes are rather apparent, giving the surface double-faced wetting characteristics. The responsive surface composition regulated wetting will be very useful in understanding wetting theory, and will be helpful experimentally in designing smart surfaces in, for example, microfluidic devices.

The surface tension and fluorescence spectra of sodium octyl-[ω-octyloxy-poly(oxyethylene)]-yl-benzene sulfonates (APEnBS) aqueous solutions have been investigated by Wilhelmy plate method and intrinsic probe methods, respectively to study the effect of EO units on their properties. It was discovered that the surface performance of these surfactants was greatly outstanding: the values of critical micelle concentration (CMC) reached to be of the order of magnitude of 10−5 mol/L, the values of surface tension at CMC, γCMC, were between 25.79 to 31.02 mN/m, and the effectiveness and efficiency of surface tension reduction were excellent. The introduction of oxyethylene units to the surfactant molecule evidently improved the solubility of APEnBS. With the increase in EO units, the CMC slightly changed after the first decreased. On the other hand, the surface excess concentration at saturation, Γ max, decreased after the first increased and γCMC increased after the first decreased accordingly. The CMC determin...

The effect of octadecanol on dilational properties of 4,5-diheptyl-2-propylbenzene sulfonate and partly hydrolyzed polyacrylamide at the decane-water interface has been examined by means of longitudinal method. The octadecanol plays different roles in influencing the structure of adsorbed layers at different bulk concentration. A small quantity of octadecanol may enhance the dilational modulus by forming densely packed mixed-adsorption layer with surfactant molecules through hydrophobic interaction, which leads to the increase of dilational modulus. However, due to the weakening of the “entanglement” among long alkyl chains in surfactant molecules by the intercalation of octadecanol, the superfluous addition of octadecanol could decrease the dilational modulus. In the case of polymer/octadecanol system, the addition of the polymer may enhance the dilational modulus due to the slow diffusion-exchange process of the polymer.

Quantitative characterization models of oil increment and water-cut change in polymer flooding called Hou's models are established in the paper. The mathematic models are concise and characteristic parameters have specific physical meanings and are easy to determine. Automatic solution method based on real-coded genetic algorithm (GA) is presented. Based on numerical simulation of polymer flooding, quantitative prediction model of production performance in polymer flooding is established through the combination of orthogonal design and support vector machine (SVM) methods, in which the combination effect of factors is considered. Taking Shengli oilfield as an example, the history matching and prediction of polymer flooding are carried out, it is indicated that there exists a good matching between the quantitative characterization model and the field data, and this model can be extrapolated. Regardless of the limited sample set, the quantitative prediction model can give consideration to both universality and generalization to meet the requirements of engineering computation application. The characterization model or prediction model can be alternatively used according to whether there is a dynamic tendency of the polymer flooding unit or not. Therefore, the models can guide the scheme programming and dynamic adjustments of polymer flooding.

Poly(acrylamide-co-sodium acrylate) (PAM/AA-Na) and poly(acrylamide-co-sodium vinylsulfonate) (PAM/VSS-Na) were prepared by inverse emulsion polymerization. The effects of CaCl2 on PAM/VSS-Na or PAM/VSS-Na aqueous solutions were investigated by steady-flow experiments at 25, 40, 55 and 70 °. The results show that the apparent viscosities of both solutions decrease with addition of CaCl2 or increase of temperature and shear rates. PAM/VSS-Na solution has better performance on the salt tolerance, shear endurance and temperature resistance due to containing sulfonic group in the molecules. Ca2+ concentration can affect the viscous activation energy of both solutions and the reason may be that these interactions between Ca2+ and also copolymer molecules are related to temperature and competitive in solution. These results may offer the basic data for searching the flooding systems with the ability of temperature resistance, salt tolerance and shear endurance for tertiary oil recovery.

Four sodium branched-alkylbenzenesulfonates with or without additional alkyl substituents were synthesized and their adsorption properties were investigated in aqueous solution and in 0.17 M NaCl solution. The critical micelle concentration (cmc), surface excess concentration at interface saturation (Γmax), surface pressure at the cmc (π cmc ), p C 20 and standard free energy of adsorption ( ) were calculated from the surface/interfacial tension measurements. It was found that the length of additional alkyl substituents had key effect on adsorptions of branched-alkylbenzenesulfonates. With increasing the carbon number of additional alkyl substituents from 1 to 3, Γmax decreased constantly, while π cmc changed a little with the decrease of Γmax at aqueous solution/air interface and NaCl solution/air interface. It was interested that one of the synthesized sodium branched-alkylbenzenesulfonates can arrive ultra-low interface tension (10−3 mN/m) at NaCl solution/nonane interface.

A column-switching anion-exchange chromatography method was described for the separation and determination of petroleum monosulfonates (PMS) and petroleum disulfonates (PDS) in crude oil that was simply diluted with the dichloromethane/methanol (60/40). The high performance liquid chromatography (HPLC) system consisted of a clean-up column and an analytical column, which were connected with two six-port switching valves. Detection of petroleum sulfonates was available and repeatable. This method has been successfully applied to determine PMS and PDS in crude oil samples from Shengli oil field.

Significant synergistic effects between sodium dodecylbenzene sulfonate (SDBS) and nonionic nonylphenol polyethylene oxyether, Triton X-100 (TX-100), at the oil/water interface have been investigated by experimental methods and computer simulation. The influences of surfactant concentration, salinity, and the ratio of the two surfactants on the interfacial tension were investigated by conventional interfacial tension methods. A dissipative particle dynamics (DPD) method was used to simulate the adsorption properties of SDBS and TX-100 at the oil/water interface. The experiment and simulation results indicate that ultralow (lower than 10(-3) mN m(-1)) interfacial tension can be obtained at high salinity and very low surfactant concentration. Different distributions of surfactants in the interface and the bulk solution corresponding to the change of salinity have been demonstrated by simulation. Also by computer simulation, we have observed that either SDBS or TX-100 is not distributed uniformly over the interface. Rather, the interfacial layer contains large cavities between SDBS clusters filled with TX-100 clusters. This inhomogeneous distribution helps to enhancing our understanding of the synergistic interaction of the different surfactants. The simulation conclusions are consistent with the experimental results.

The application of resol as a crosslinking agent with polyacrylamide has become widespread, but it is not clear for forming mechanisms of extraordinarily high activity of the resol. In this research, the major components of the resol and their mass percentage are investigated by Liquid chromatography-mass spectrograph, the mechanism of forming the components is exploited. The evolution of formaldehyde, phenol, and first formed addition products were quantitatively traced by titration and high-performance liquid chromatography, furthermore the kinetics of synthesis is studied based on the analyzing results. The results show that the resol is composed of nine compounds and the sum of percentage for each integral area is more than 99%. In addition, the constant of overall reaction rate k consists of three values of 5.667 × 10−5, 7.236 × 10−5, and 23.05 × 10−5 s−1, which means that the reaction can be separated to three stages of hydroxymethylphenol (HMP) producing stage, dihydroxymethylphenol (DHMP) and trihydroxymethylphenol (THMP) producing stage and condensation stage. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Microenvironmental properties of alkylbenzenesulfonates micelles with different alkyl substituents were investigated by the fluorescence probe technique. The results showed that the micropolarity of micelles decreased and the microviscosity of micelles increased with lengthening of additional short alkyl substituents, while the micropolarity of micelle was unchanged and the microviscosity of micelles increased obviously with increase of the branched-alkyl chain. The different steric effect between additional alkyl chain and branched-alkyl chain affected the self-aggregation behavior of surfactants strongly.