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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 array behaviour of anionic surfactant sodium dodecylbenzenesulfonate (SDBS) on the air/water interface was investigated using non-resonant surface second harmonic generation (SHG) and molecular simulation. It was found that the SHG intensities changed with surfactant concentrations non-monotonously under Critical Micelle Concentration (CMC). The mean orientational angle of SDBS molecule at the air/liquid interface was calculated, and the molecular array behaviour was analyzed by molecular dynamics (MD) simulation. The simulated results agreed with the experimental results very well, which provided the detailed information about the interfacial molecular configuration of surfactant, not only indicating the SHG intensity related to the Ns and r(θ), but also demonstrates that the microscopic information presented by the MD simulation method is reliable. According to the results, the surfactant molecules get clustered even at very low concentration far lower than the CMC.

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.

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 rheological properties of series branched betaine surfactants: Guerbet p-(n-tetradecyl)-benzyl carboxybetaine (C14GCB), Guerbet p-(n-dodecyl)-benzyl polyoxyethylene ether(2) carboxybetaine (C12GE2CB), Guerbet p-(n-tetradecyl)-benzyl polyoxyethylene ether(2) carboxybetaine (C14GCB) and Guerbet p-(n-hexadecyl)-benzyl polyoxyethylene ether(2) carboxybetaine (C16GCB), were investigated by drop shape analysis method at the water-decane interface. The dilational properties of surfactants were investigated as a function of time, frequency and concentration. The experimental results show that the time dependence was complex. It was also found that the dilational modulus were almost independent of frequency in the experimental concentration range for C14GE2CB and C16GE2CB, while the dilational modulus of C14GCB and C12GE2CB increased with the increase of frequency, sharing the same results with conventional zwitterionic surfactants. The results indicated the appearance of a more elastic film for the C14GE2CB and C16GE2CB due to the internal compression and expansion of oxyethylene units (EO). On the other hand, the surfactant with branched alkyl chain came forth a higher maximum value of dilational modulus compared with the straight chain surfactants with the increase of concentration, which means the branching of alkyl chain was another important factor to control the interfacial film.

In this paper, the molecular array behavior of the mixed systems of anionic–nonionic surfactant sodium alcohol ether sulphate (AES) and zwitteroinic surfactants carboxyl betaine (CAB) or sulfobetaine (DSB) at the gas/water interface in foam films was investigated by molecular dynamics simulation approach, which helped to understand in microscopic view how salts effected the foam stability of the mixed surfactants and their synergistic effect. It was found that the multivalent inorganic cations could be bounded to the negatively charged head groups of the surfactants and participated in the formation of the interface layer directly, not only influenced the interfacial adsorption behavior of the surfactant molecules, but also changed the state of the water molecules in the foam films. Foam decay method was utilized to determine the foam stability experimentally. The experimental results agreed very well with the simulation results. The knowledge about how the microscopic character of the surfactant mixtures at the interface with multivalent cations coexisting effect the foam properties could provide useful guidance for the application of surfactants under high salinity condition, such as the formula design for foam flooding system used in offshore enhanced oil recovery (EOR).

The dynamic interfacial tensions (IFTs) of enhanced oil recovery (EOR) surfactant/polymer/organic alkali systems against a homologous series of alkanes have been investigated by a spinning drop interfacial tensiometer. Two organic alkalis with different molecular sizes, ethanolamine (EA) and diethanolamine (DEA), two surfactants with high interfacial activity, heavy alkyl benzenesulfonate (HABS) and petroleum sulfonate (SLPS), and two kinds of polymers, partly hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM), were employed to study the real mechanisms controlling the IFT behavior. The experimental results show that the addition of organic alkali may affect the dynamic IFTs of surfactant solutions through different mechanisms. First, the possible reaction of organic alkali with the oil-soluble components in industrial surfactants will influence the surface active spices at the interface and enhance the dynamic behavior. Second, the hydrophilic–lipophilic balance (HLB) of...

A novel method for the chemical fingerprinting of petroleum sulfonates has been developed. In the present study, crude oil existing in petroleum sulfonate samples is first obtained and then is analyzed by gas chromatography. Characteristic chromatographic profiles of different brands or sources of samples are established. Pattern recognition of the chromatograms is performed using multivariate data analysis. As a result, the total 15 tested samples and 8 validated samples can be well evaluated by the standards established in the article, which are in accordance to the results of interfacial tension of each sample. The method has successfully been applied to discriminate between different petroleum sulfonates, and it seems to be very promising for a variety of other applications.

Synergism of water-soluble hydrophobically associating polyacrylamide (HA-PAM) with nonionic surfactant laurel alkanolamide (LAA) was investigated via the rheology, fluorescence spectroscopy and dissipative particle dynamics (DPD) simulation methods. The viscosity and elasticity of HA-PAM solutions increased in a large LAA concentration range, which was principally ascribed to the crosslinking effect of LAA by aggregating to the hydrophobic chains of HA-PAM molecules as confirmed by the DPD simulation and experimental results. The crosslinking effect was enhanced in the presence of an appropriate amount of electrolyte or with increasing temperature in the studied temperature range of 20–70 °C. Thus, the LAA not only significantly enhanced the salt resistance of HA-PAM but also retarded the decrease of the viscosity and elasticity of the HA-PAM solutions at high temperature. The HA-PAM/LAA binary systems exhibit great potential for application in tertiary oil recovery of oil fields with high salinity.

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 influences of nonionic surfactant on interfacial properties of anionic–nonionic surfactant against alkanes are studied by measuring the dynamic interfacial tension (IFT). The surfactants chosen are fatty alcohol polyoxyethylene carboxylate (C12EO3C) and fatty alcohol polyoxyethylene (C12E3) with various counterions, Na+, Mg2+, and Ca2+. On the basis of our experimental results, one can find that the addition of nonionic surfactants C12E3 could achieve an ultralow IFT value at some specific alkane carbon numbers under NaCl condition and the obvious synergistic effect on reducing IFT can be observed during all experimental alkane carbon numbers. However, for MgCl2 systems, the ultralow IFT values can be achieved by pure C12EO3C solutions and one can observe synergistic effect and antagonistic effect on IFTs at higher and lower alkane carbon numbers respectively by adding nonionic surfactant. On the other hand, for CaCl2 systems, the addition of 0.05% C12E3 shows the same influence on the IFTs as that of NaCl systems, while the similar effect as that of MgCl2 systems will be observed when adding 0.1% C12E3. An interfacial model combined two mechanisms, controlling hydrophilic–lipophilic balance and forming mixed adsorption film, responsible for varying IFT has been provided based on the difference of ion radius. By adding nonionic surfactant, the mechanisms of forming mixed adsorption film and controlling hydrophilic–lipophilic balance play crucial roles in effecting IFTs for NaCl systems and MgCl2 systems, respectively. Moreover, for CaCl2 systems, the responsible mechanism of forming mixed adsorption film will change into controlling hydrophilic–lipophilic balance with the increase of nonionic surfactant concentration.

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.

Stimuli-responsive polymer brushes modified surfaces and binary polymer surfaces can be created on an initiator terminated substrate via surface initiated atom-transfer radical polymerization (SI-ATRP), in which the growth kinetics can be modulated by Cu(II) ratio. As stimuli-responsive brushes, many environmental triggers can drive their conformation change such as pH and salt concentration. The external-stimuli modulated reversible conformational changes of polymer brushes can influence the charge transport behavior investigated by electrochemistry method, which have potential applications in in situ switching ion permeability and charge transport. The charge transport of binary polymer brush can be switched on or off by different ion flexibly which is an electrochemical logic switch.

The interfacial activity of surfactants is an issue that attracts considerable attention. However, most of the literature focuses on pure surfactants, and the effect of impurities on surfactant activity remains an elusive puzzle in the understanding of structure–performance relationships. In this paper, the nonionic surfactant laurel alkanolamide (LAA) synthesized by a one-step method was found to decrease the oil–water interfacial tension to ultra-low values at low concentration without co-surfactants. LAA also had surprising oil phase adaptability, making it a perfect model not only to study the theoretical mechanism for obtaining ultra-low interfacial tension, but also for distinguishing the contribution of the molecular interfacial array behaviour of surfactants and concomitants (defined as the residual reactants and by-product) on the interfacial activity. The oil–water interfacial activity of LAA with or without concomitants was investigated experimentally and theoretically using dissipative dynamic simulation (DPD). The detailed molecular array behaviour of LAA and the concomitants at the oil–water interface was investigated by molecular dynamics (MD). The concomitants were found to coexist with LAA at the oil–water interface and distribute at different positions in the interfacial layer, resulting in the high interfacial activity and oil phase adaptability. The experimental results agree well with the simulation results. We hope our strategy can provide an avenue to understand the structure–performance relationship of surfactants at the molecular level and reveal an effective approach to obtaining ultra-low interfacial tensions with different oil phases.

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 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.

This article aims to compare the interfacial activities of different kinds of surfactants in the same oil/water system. The anionic surfactants of alkylbenzene sulfonates, the polyoxyethylenated nonionic surfactants, the cationic surfactants of alkyl trimethyl ammonium chlorides, and the zwitterionic surfactants of alkyl hydroxyl sulfobetaines were used, and the interfacial tensions of the surfactant solutions against kerosene at different NaCl concentrations were measured. It is found that the interfacial activities of the alkylbenzene sulfonates are high and ultralow interfacial tensions (

Reservoir wettability plays an important role in various oil recovery processes. The origin and evolution of reservoir wettability were critically reviewed to better understand the complexity of wettability due to interactions in crude oil-brine-rock system, with introduction of different wetting states and their influence on fluid distribution in pore spaces. The effect of wettability on oil recovery of waterflooding was then summarized from past and recent research to emphasize the importance of wettability in oil displacement by brine. The mechanism of wettability alteration by different surfactants in both carbonate and sandstone reservoirs was analyzed, concerning their distinct surface chemistry, and different interaction patterns of surfactants with components on rock surface. Other concerns such as the combined effect of wettability alteration and interfacial tension (IFT) reduction on the imbibition process was also taken into account. Generally, surfactant induced wettability alteration for enhanced oil recovery is still in the stage of laboratory investigation. The successful application of this technique relies on a comprehensive survey of target reservoir conditions, and could be expected especially in low permeability fractured reservoirs and forced imbibition process.

In the present work, the influences of different types of electrolytes on interfacial dilational properties of anionic surfactant sodium 4,5-diheptyl-2-propylbenzene sulfonate 377 and asymmetrical anionic Gemini surfactant C 12 COONa-p-C 9 SO 3 Na in the absence or presence of 1500 ppm partly hydrolyzed polyacrylamide were studied at decane–water interface, respectively, by means of interfacial tension relaxation measurements. The decay curves of interfacial tension were fitted by the summation of a number of exponential functions. The dilational elasticity ( ɛ r ) and dilational viscosity component ( ɛ i ) were calculated by Fourier transform and displayed as Cole–Cole plots (plotting ɛ i or ɛ i / ɛ 0 as a function of ɛ r or ɛ r / ɛ 0 respectively). The experimental results show that only single reorientation process dominates the interfacial properties in the presence of any electrolyte for 1 × 10 −6 mol L −1 377 solution, resulting form the more compacted film by electrostatic screening. On the other hand, the contribution of reorientation process at higher frequency decrease after the addition of NaCl and there exists no pure reorientation process in the presence of CaCl 2 or MgCl 2 for Gemini surfactant because of the slight increase of interfacial concentration due to larger molecular size and strong steric hindrance between alkyl chains. The addition of polymer can significantly modify the dilational properties of adsorbed surfactant layer due to the formation of mixed adsorption film through hydrophobic interaction between polymer chain and alkyl chain of surfactant molecule. The normalized Cole–Cole plots of surfactant-polymer films with different types of electrolytes show the similar characteristic in general and no pure reorientation process can be observed in any case.

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.

In this article, foaming properties, dynamic surface tension, and surface dilational properties were carried out with aqueous solutions of polyoxyethylene alkyl ether carboxylic salts to elucidate the relationship between foaming properties and surfactant structures. It was found that the dynamic surface tension of the solution is the key factor in determining the foamability: with increasing in the length of the hydrophobic group, dynamic surface activity becomes low, which leads to the low foam volume; the surfactant with branched-alkyl chain has faster diffusion rate, which lead to higher dynamic surface activity and higher foam volume. However, for straight chain surfactant, the foam stability is correlated with the surface dilational properties: the change rule of surface dilational modulus is consistent with that of the foam stability.

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.

Molecular dynamics simulations on the interface between liquid water and liquid n-alkane (including octane, nonane, decane, undecane and dodecane) have been performed with the purpose to study the interfacial properties: (I) density profile; (II) molecular orientation; (III) interfacial tension and the temperature effect on the interfacial tension. Simulation results show that at the interface the structures of both water and n-alkane are different from those in the bulk. Water has an orientational preference due to the number of hydrogen bonds per molecule maximized. N-alkane has a more lateral orientation with respect to the interface in order to be in close contact with water. The calculated individual phase bulk density and interfacial tension of water/n-alkane systems are in good agreement with the corresponding experimental ones.

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.

This present article employs four anionic Gemini surfactants with different spacer groups and investigates their physicochemical and aggregation properties. The critical micelle concentration (CMC), surface tension at CMC (γCMC) and C 20 of these surfactants have been investigated using the du Nouy ring method. The aggregation number (N) was determined with intrinsic fluorescence quenching method using pyrene as a fluorescence probe and benzophenone as a quencher. Results show that these anionic Gemini surfactants have lower CMC and C 20 values compared with those conventional ones and show higher surface activity. As expected, the spacer plays an important role in the aggregation properties of Gemini surfactants. Under experimental conditions, Gemini B–D with an alkoxylated group as spacer has a lower CMC and a higher aggregation number than Gemini A with methylene as spacer. For Gemini B–D, the CMC and aggregation number values decrease with the increasing flexible spacer length. The micropolarity also affects the aggregation of the present anionic Gemini surfactants. The micropolarity of micelle becomes low when the concentration of surfactants increases. Aggregation numbers of surfactants increase and fluorescence intensities decrease with the increasing concentration of NaCl. These results will help us to understand the relationship between the architectures of Gemini surfactants and their various properties in aqueous solution.

The microscopic flow mechanism of polymer flooding was examined using an industrial microfocus computerized tomography system. On the basis of scanned slices acquired in the process of water flooding and polymer flooding, three-dimensional visualization of oil and water distribution in different flooding conditions was achieved with a series of image processing methods, including pre-processing, interpolation, segmentation, and three-dimensional construction, which are effective techniques for both the qualitative description and the quantitative characterization of the microscopic flow mechanism. This study has confirmed the suggestion that the displacement efficiency of polymer flooding is higher than that of water flooding, and effectively revealed the microscopic mechanism of oil recovery in polymer flooding. The water/oil mobility ratio was improved after polymer flooding, which resulted in a break of the “equilibrium” flow field that was formed during water flooding and the redistribution of the regions of oil saturation. The remaining oil was flushed out as the result of the flow redirection and the viscoelastic effect of polymer flooding. Compared to water flooding, polymer flooding increased the microscopic sweep efficiency as well as the microscopic displacement efficiency, and thereby the ultimate oil recovery.

The construction of a network model is one of the key techniques in organic combination of microscopic flow experiment and simulation. The construction method of a three-dimensional network model is presented on the basis of CT scanning images in this paper. A series of CT slice images describing microscopic pore structure and fluid distribution of actual rock is obtained with the help of the industrial microfocus CT system. Based on the extraction of pore space skeleton, pore and throat information, the corresponding network model is established, and the conversion from three-dimensional CT image information to pore-throat size distribution and topological information is also achieved. The feature of this method lies in the fact that complicated pore space of rock may be characterized by pores and throats with a simple shape while keeping the geometry and flow characteristics. It is indicated that the calculated results of porosity, permeability, relative permeability curve and microscopic remaining oil distribution match very well the experimental results of water flooding and polymer flooding. This network model may fairly well characterize the rock microscopic pore-throat size and topological characteristics.

Core-shell type multiarm star copolymers with poly(e-caprolactone) (PCL) as shells and hyperbranched polyethylenimine (PEI) as core have been successfully prepared by the Sn(Oct)2 catalyzed ring-opening polymerization of e-caprolactone (CL) using high molecular weigh PEIs directly as macroinitiators. The initiation efficiency is in the range of 91–95% for PEI with Mn = 104 (PEI10K) and only around 60% for PEI with Mn = 2.5 × 104 (PEI25K), leading to star polymers with an average arm number in the range of 155–276. The thermal property of the obtained multiarm star polymers were also investigated by DSC. The melting and crystallization temperatures of the star polymers increase as the PCL arm length increases when the PEI core is fixed. The fusion enthalpy, crystalline enthalpy and degree of crystallinity values of the star polymers with PEI10K core are less than those with PEI1.8K core. Due to the polarity difference between PCL arm and PEI core, the resulting multiarm star polymers can act as inverted micellar nanocapsules capable of extracting and encapsulating water soluble guests. Increasing the size and polarity of the hydrophilic PEI core of the star nanocapsules are two effective ways to enhance their hydrophilic guest encapsulation capacity. Increasing the hydrophobic PCL arm length can increase the molar ratio, whereas reduce the weight ratio of the encapsulated hydrophilic guests to the star nanocapsules. Unexpectedly, the obtained nanocapsules can entrap the bigger size hydrophilic congo red guests more than the smaller size methyl orange.

The objective of this prospective study was to investigate further the clinical features of patients with giant cell (temporal) arteritis (GCA). All patients diagnosed from July 1999 to March 2001 at the Department of Neurology of the Second Xiangya Hospital in China were included. The final diagnosis was based on clinical manifestations, a temporal artery biopsy, response to steroid, and follow-up. The American College of Rheumatology (ACR) criteria for the classification of GCA were tested in the patients identified. Sixteen patients with GCA were identified; 13 (81.25%) patients fulfilled the 1990 ACR criteria for the classification of GCA. Clinical findings included the following: mean age at disease onset 43.13 years (range 28-60) and 81.25% of the patients under the age of 50 when the disease began; men 93.75%; the common initial symptoms including new headache 62.50% and visual symptoms 18.75%; the common clinical findings at presentation including new headache 93.75%, temporal artery abnormality 81.25%, visual abnormality 56.25%, and fever 25.00%; raised erythrocyte sedi mentation rate (ESR) 68.75%; and uncommon findings including jaw claudication, ptosis, fatigue, syncope, hemiparesis; all 16 patients underwent a temporal artery biopsy; inflamma tory cell infiltration 68.75% in arterial wall, fragmented internal elastica 100.00%, fibrinoid necrosis 18.75%, smooth muscle cell changes 62.50%, and thrombosis in the lumen 31.25%. The mean time from symptom onset to suspicion of GCA or biopsy was 5.52 months (range 0.25-24.33); the initial diagnosis was wrong in 87.50% of patients. These examples are too small a number to permit definite conclusion. But the results suggest that GCA may not be a rare disorder in China, mean age at disease onset was relatively young, males may be more susceptible, the clinical features of GCA have not been widely appreciated yet, there was a delay between diagnosis and treatment, and initial diagnosis was wrong in many patients.

As an intrinsically surface-specific technique, Second Harmonic Generation (SHG) is widely used in the study of interface in recent years. The SHG signals from the air/liquid interface of Rhodamine B and Sodium Dodecyl Benzene Sulfonate (SDBS) aqueous solutions were obtained and analyzed, which demonstrate that the SHG signal intensity of Rhodamine B is stronger than that of SDBS. Compared with one single solution, the SHG signal intensity of the mixed aqueous solution of Rhodamine B and SDBS decreases. From the UV-VIS absorption spectrum of the two aqueous solutions, it can be seen that Rhodamine B has an absorption peak closer to the second harmonic frequency. Therefore the resonance of the second harmonic frequency with the frequency of the dipole transitions of the chromophore considerably enhances the signal intensity. Furthermore, the hyperpolarizabilities of the molecules of Rhodamine B and SDBS are calculated from first-principles, which reveal that the hyperpolarizability of Rhodamine B molecule is greater than that of SDBS molecule. When they are mixed, molecules of Rhodamine B and SDBS gather together because Rhadamine B molecule carries positive surface charge and SDBS is anionic surfactant, causing the decrease of the SHG intensity of the mixed solution.

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.

Water slips exist over superhydrophobic solid surfaces, but the slip flow of diverse liquids on a single surface has not been deliberately studied to date. Here, we report the slip flow behavior of a variety of liquids with different surface tensions and viscosities on a robust omniphobic surface. This surface displayed a dramatic slippage effect and thus a high drag reduction efficiency of approximately 10-20% for all liquids, depending on both liquid viscosity and surface energy. The observed liquid slip was attributed to the surface dual micro/nanostructure and the low-surface-energy coating.

A novel compound of an imidazolium type of ionic liquid (IL) containing a biomimetic catecholic functional group normally seen in mussel adhesive proteins was synthesized. The IL can be immobilized on a silicon surface and a variety of other engineering material surfaces via the catecholic anchor, allowing the tribological protection of these substrates for engineering applications. The surface wetting and adhesive properties and the tribological property of the synthesized self-assembled monolayers (SAMs) are successfully modulated by altering the counteranions. The chemical composition and wettability of the IL SAMs were characterized by means of X-ray photoelectron spectroscopy (XPS) and contact angle (CA) measurements. The adhesive and friction forces were measured with an atomic force microscope (AFM) on the nanometer scale. IL composite films were prepared by spin coating thin IL films on top of the SAMs. The macrotribological properties of these IL composite films were investigated with a pin-on-disk tribometer. The results indicate that the presence of IL SAMs on a surface can improve the wettability of spin-coated ionic liquids and thus the film quality and the tribological properties. These films registered a reduced friction coefficient and a significantly enhanced durability and load-carrying capacity. The tribological properties of the composite films are better than those of pure IL films because the presence of the monolayers improves the adhesion and compatibility of spin-coated IL films with substrates.

Gas injection into tight oil reservoirs, as a secondary recovery technique, can be favorable and promising in terms of high gas injectivity and good displacement/sweeping efficiency over water injection. Particularly, CO2 injection is the best option due to its superior miscibility effect with oil and in consideration of geological storage of the greenhouse gas. In this study, CO2 injection into a tight oil reservoir for IOR is assessed and a pilot project is underway. The reservoir is located in the G89 Block of Shengli Oilfield East China, which has very poor water injectivity due to very low permeability of less than 5 mD in average, and has been producing via natural depletion since 2005. The original reservoir pressure was over 40 MPa, and the reservoir temperature of 126 . A CO2 injection and storage program has been proposed, and CO2 will be from a coal-fired power plant 30 km away under a Sinopec’s CCS (Carbon Capture and Storage) scheme. Laboratory investigation includes PVT experiments, slim tube test and core flooding/displacement experiments, in order to study the miscibility effect and displacement efficiency via CO2 injection at various conditions. Reservoir simulations were performed to predict the IOR potentials of CO2 injection at different pressures, namely at immiscible, miscible and near-miscible modes. The MMP (Minimum Miscibility Pressure) of the reservoir oil is determined as over 29 MPa, while the reservoir pressure at the beginning of CO2 injection was around 23 MPa after several years’ depletion. Therefore, CO2 flooding at a near miscible mode will prevail. A field pilot of CO2 injection at current reservoir conditions (at near-miscible mode) is designed and its performance is presented in the paper. Introduction Injection of CO2 into oil reservoirs may develop different displacement or flooding processes, namely miscible, immiscible and near-miscible, which mainly depend upon the operating pressure, oil and reservoir characteristics. Miscible displacement is the most preferable mechanism for oil recovery with respect to high displacement and sweeping efficiency (Jeschke et al. 2000). However, miscible displacement is only realizable at pressure greater than MMP; therefore miscibility can be difficult to develop in many cases, such as mature oilfields due to the depletion of reservoir energy, and in low permeability reservoirs where a large pressure drop or difference may develop from injector to producer. The miscibility of oil and CO2 is also affected by compositions of crude oil and purity of CO2, rock heterogeneity and gravity segregation (Johns et al. 2002). Compared with miscible flooding, immiscible flooding is less effective, particularly for reservoirs with serious heterogeneity, in which high permeability channels, inverse mobility ratio and viscous “fingering” can lead to early gas breakthrough (Aziz et al. 2009; Zhang et al. 2010). For those reservoirs with relatively low pressure and less favorable for miscibility, a near-miscible process might be developed to maximize the interactions of oil and CO2 and achieve high oil recovery. In recent years, the concept of near-miscible CO2 flooding has been received more and more attention. The research of near-miscibility effect can be tracked back to early 1980s’, when Orr and colleagues (Orr et al. 1981) published their studies on phase behavior of CO2/crude oil mixture, they indicated that the inflexion point in the slim-tube experimental curve may not necessarily signify the transition from immiscible to miscible displacement, instead it can represent a near miscible state because a full miscibility is not achieved, whereas this “near-miscible” phase behavior can be also good for effective oil displacement. Shyeh-Yung and J-G, J (1991) pointed out that a near-miscible CO2 IOR process has potential to economically recover oil. Hadlow (1992) stated that application of CO2 flooding in reservoirs where a near miscible condition exists can be one of the most significant opportunities for utilization of CO2. Case studies by Thomas et al. (1994) showed that many reservoirs historically designed as miscible flooding would be better described as near miscible. It

Based on the analysis results with rheometer, spining drop interfacial tensionmeter, laser particle analyzer, microscopic oil displacement and oil displacement, a novel Preformed Particle Gel (PPG) for chemical EOR was screened out. Its application properties were evaluated. A new chemical flooding system, Heterogeneous Combination Flooding System (HCFS), was designed according to the interaction laws of PPG, polymer and surfactant. Core flooding tests were conducted under two types of reservoir conditions of Shengli Oilfeild, 1) high temperature and high salinity (HT/HS) conditions, and 2) after polymer flooding reservoir condition, to figure out the enhanced oil recovery effects of HCFS. It showed that PPG can not only migrate and penetrate in porous medium, but also generate more significant volumetric sweep efficiency by the cycle of piling up-plug-pressure rising-extending and deforming to pass through porous throats than the conventional polymer flooding to modify the existing dominant migration path. Because of the enhanced sweep efficiency introduced by the mixed PPG-polymer system with higher viscosity and viscoelasticity as well as the displacement efficiency by surfactant system, HCFS can improve the oil recovery by 22.5% for HT/HS reservoirs and by 19.1% for after the polymer flooding reservoirs in dual sandpacked tube flooding experiments with the interlayer heterogeneity of 1000:5000 × 10−3μm2.

The adsorption behavior of zwitterionic surfactant dodecyl sulfobetaine (DBS) on a silica/solution interface with Ca(2+), Mg(2+) existing in aqueous solution is explored by atomistic molecular simulations. The interaction energy contribution of van der Waals and electrostatic potentials in the surfactants/water/silica system are respectively calculated, from which the electrical interaction can be found to play a decisive role in the adsorption tendency of DBS on the silica surface with or without inorganic ions, despite different mechanisms. The distinct decrease of energy has been found to be derived from electrical interaction when DBS adsorb on the silica surface covered by Ca(2+) or Mg(2+). Therefore, it can be predicted that the cationic ions combined on the negatively charged silica surface in a mineral water medium might decrease the adsorption trend of DBS on the silica surface, which has been experimentally proven by TOC measurement. Structural information of the close interface layer and the distribution of water molecules are analyzed after the complete molecular dynamics simulation using a ternary model. Ca(2+) and Mg(2+) combined on the silica surface can reduce the adsorption amount of DBS by preventing the direct interaction between DBS and surface, and bringing about the orientation reversal of DBS molecules to break the order of adsorption interface layer. Furthermore, changes in the status of the water spreading on the silica surface caused by the complexation of cations are also an important reason in the adsorption reduction.

Abstract As the second largest oilfield in China, Shengli oilfield has been one of the largest oil-bearing regions performing polymer flooding in the world. However, varieties of reservoirs and complex reservoir conditions in part of blocks have been the obstacle in performing polymer flooding. At the same time, those blocks where polymer flooding has been conducted are facing the problem of how to improve oil recovery further. Laboratory experiment and field performance of enhanced foam flooding pilot are described in this paper. The enhanced foam flooding involves a complex system consisting of polymer, foam agent and nitrogen gas, which has a larger value in apparent viscosity. Comparing with polymer flooding, enhanced foam flooding has a better capability in profile control and oil flooding in improving oil recovery. Laboratory experiments indicate that the flow resistance for enhanced foam in porous media is much larger than that when each of its components flows individually. Pressure gradients have a uniform distribution, which can avoid end-side blocking. Enhanced foam flooding conducted at Chengdong block is the first well group test in Shengli oilfied. The test consists of four injection wells, three central production wells and nine edge production wells. Field test performance shows that the enhanced foam flooding improves the injection profile of reservoir and increases injection pressure. Therefore, preliminary water decreasing and oil increasing are achieved. The total water cut for well group has decreased from 95.9% before the test to current 88.6%. And daily oil production has been improved from 4.5t to 22.6t. Therefore, besides of polymer flooding, enhanced foam flooding is expected to be a new industrial method to improve oil recovery in Shengli oilfield. Introduction Several major oilfields in eastern China have entered the mid and late period of development, so it becomes very urgent for these old oilfields to enhance oil recovery. Foam flooding is a kind of tertiary recovery which uses foam as oil displacement medium, due to high apparent viscosity, strong ability of profile control and selectivity for oil/water blocking. It can improve the fluid apparent viscosity, increase the sweep area, and has strong ability of blocking and profile control, so it can be used successfully in the oilfields.1, 2 Foam is a kind of pseudo-plastic fluid which has special migration law in porous media.3 According to the reservoir characteristics of Shengli oilfield, enhanced foam flooding has been carried out, and a complicated multi-component system consisting of polymer, foam agent and nitrogen gas has been injected in the reservoir. In this paper, Chengdong oilfield is selected for discussion. Laboratory experiment and field performance of enhanced foam flooding pilot are described in this paper. They show that the enhanced foam flooding is a very effective tertiary oil recovery method and has good commerical prospect in the Shengli oilfield. Experimental Description Experimental Devices and Materials According to different experimental purposes, we use two types of displacement devices: core displacement device and long slim tube displacement device.

There is a close correlation between the interfacial activity and the adsorption of the surfactant at the interface, but the detailed molecular standard information was scarce. The interfacial activity of two traditional anionic surfactants sodium dodecyl benzene sulfonate (SDBS) and sodium oleate (OAS) were studied by experimental and computer simulation methods. With the spinning drop method and the suspension drop method, the interfacial tension of oil/aqueous surfactant systems was measured, and the influence of surfactant concentration and salinity on the interfacial tension was investigated. The dissipative particle dynamics (DPD) method was used to simulate the adsorption of SDBS and OAS at the oil/water interface. It was shown that it is beneficial to decrease interfacial tension if the hydrophobic chains of the surfactant and the oil have similar structure. The accession of inorganic salts causes surfactant molecules to form more compact and ordered arrangements and helps to decrease the interfacial tension. There is an osculation relation between interfacial density and interfacial activity. The interfacial density calculated by molecular simulation is an effective parameter to exhibit the interfacial activity.