Rheological properties of wormlike micelles formed in the sodium oleate/trisodium phosphate aqueous solution

Aqueous solution of anionic surfactant,sodium oleate（NaOA）,was studied by means of steady-state shear rheology and dynamic oscillatory technique.The system of NaOA/Na3PO4 showed high viscosity,strong viscoelasticity and good ability of countering Ca^2＋,Mg^2＋.The Maxwell model and Cole-Cole plot were applied to study the dynamic viscoelasticity of wormlike micelles.The microstructures of the wormlike micelles were characterized by FF-TEM.

Molecular origin for pH-responsive wormlike micelles of zwitterionic surfactants triggered by aromatic acid derivatives

Introduction of aromatic acid derivatives(AADs)into zwitterionic surfactants is an efficient method to prepare wormlike micelles with pH-controllable viscosity;however,the coincident molecular origin of AAD/zwitterionic surfactant binary mixtures remains unclear.Herein,the self-assembly of hydroxyl derivatives of benzoic acid(BA)and cetyldimethyl betaine(BS-16)mixtures in water was systematically assessed,and various factors,such as the molecular structure,molar ratio of AAD and BS-16,and solution pH,were investigated.The structure-property relationship of AAD/BS-16 binary mixtures was established,which provided the molecular origin for the effect of AAD on micellar microstructures and the pH-induced morphological transitions.The ortho-substituted hydroxyl moiety in the BA molecule facilitated the formation of larger wormlike micelles,whereas the effect of the meta-substituted moiety was less significant.The para-substituted hydroxyl moiety in BA did not favor micellar growth.This moiety exhibited similar characteristics to the increasing hydroxyl moiety number in the AAD molecules or solution pH where the negative effects of steric hindrance and electrostatic interactions of molecules in micelles aredominant.

A robust viscoelastic surfactant tolerating 20% HCl up to 150℃ for oil well stimulation

Viscoelastic surfactants(VES)are often used as viscous diverters in acidizing stimulation to prolong the acid consumption time and maximize zonal coverage of the acid for improving well productivity.However,the ceiling temperature of commercial VES cannot exceed 120℃in practical use because of the poor thermal stability and fragile molecular structure,hindering their implementation in hightemperature oil reservoirs,i.e.,≥150℃.Here we synthesized a novel C22-tailed diamine,N-erucaminopropyl-N,N-dimethylamine(EDPA),and examined comparatively its rheological behavior,assemblies morphology and molecular stability in 20 wt%HCl with a commercial VES,erucyl dimethyl amidopropyl betaine(EDAB).The feasibility of EDPA for acidizing stimulation was assessed by acid etching of carbonate rock with its HCl solution at 150℃.Rheological results showed that the 2.5 wt%EDPA—20 wt%HCl solution maintains stable viscosity of 90 m Pa s at 150℃for 60 min,while that of 2.0 wt%EDAB HCl solution is just 1 m Pa s under identical conditions.1H NMR spectra and cryo-TEM observations revealed that the chemical structure and self-assembled architectures of EDPA remained intact in such context,but the EDAB suffered from degradation due to the hydrolysis of the amide group,accounting for the poor heat-resistance and acid-tolerance.The reaction rate of 2.5 wt%EDPA HCl solution with carbonate rock was one order of magnitude lower than that of 20 wt%HCl solution at 150℃,underpinning the potential of EDPA to be used in the high-temperature reservoirs acidizing.This work improved the thermal tolerance of VES in highly concentrated HCl solution,paving a feasible way for the acidization of high-temperature reservoir environments(~150℃).

A systematic rheological study of alkyl amine surfactants for fluid mobility control in hydrocarbon reservoirs

The basis of this study is to identify the versatility of N,N,N＇-trimethyl-N＇-tallow-1,3-diaminopropane（DTTM） surfactant in high saline environments. The surfactant was examined with sodium chloride, NaCl, to understand how triggers such as salt, p H, temperature, and surfactant concentration influences the viscoelastic response of the surfactant solution. The DTTM surfactant and salt（NaCl） concentrations used in steady-state shear viscosity analysis range from 0.2 wt% to 2 wt%and 5 wt% to 25 wt%, respectively. Along with DTTM results, three similar chemical structures are investigated to understand how viscosity changes with alterations in tail and head group composition. It was found that DTTM surfactant has the capability of transitioning from a foam-bearing to viscoelastic state at low surfactant concentrations under moderate to high saline conditions. A longer tail length promotes viscoelasticity and shear-thinning behavior. Terminals consisting of hydroxides or ethoxylates have a lower viscosity than that of methyl terminals. A head group consisting of two nitrogen atoms has a higher viscosity than those containing one nitrogen atom. The rheological characterization of DTTM presented in this paper is part of a larger study in determining the capability of this surfactant to foam CO2 for improving mobility control in CO2 enhanced oil recovery in high saline oil formations.

Synergistic Effect of Cocamidopropyl Betaine and Sodium Lauroyl Sarcosinate

In this study,we investigated the synergistic effect of a zwitterionic surfactant(cocamidopropyl betaine)and amino acid surfactant(sodium lauroyl sarcosinate)by measurements of surface tension,rheological properties,dynamic light scattering(DLS),and transmission electron microscopy(TEM).The results confirm the formation of wormlike micelles in the mixed system,which leads to superior surface activity as compared to that of an individual surfactant.Stable and dynamic viscoelastic measurements were also performed to explore the characteristics of wormlike micelles at different mole fractions,p H values,and temperatures.The results indicate that the strongest wormlike structure formed under the conditions of X_(1)=0.5,pH=4.7,and C T=600 mmol/L.The size and morphology of the mixed micelles were obtained by DLS and TEM.The results of this work offer insight into the interaction between zwitterionic and amino acid surfactants,which will contribute to the design of complex surfactants.

Wormlike Micelle Formation and Rheological Behavior in the Aqueous Solutions of Mixed Sulfate Gemini Surfactant without Spacer Group and Dodecyltrimethylammonium Bromide

The rheological behavior of the aqueous solutions of mixed sulfate gemini surfactant with no spacer group, referred to as d-C12S, and dodecyltrimethylammonium bromide （C12TABr） at a total concentration of 100 mmol,L-1 but different molar ratios of ClzTABr to d-C12S （a1） was investigated using steady rate and frequency sweep measurements. The wormlike micelles were formed over a narrow a1 range of 0.20-0.27. The viscoelastic solutions exhibited Maxwell fluid behavior. At the optimum molar ratio of 0.25, the zero-shear viscosity was as high as 600 paos and the length of the mixed wormlike micelle was about 0.45-0.85 pm. The present result provides an exam- ple to construct long wormlike micelles by anionic gemini surfactant.

Rheological study of nanoparticle-based cationic surfactant solutions

Worm-like micelles are of special interest among the many forms of surfactant aggregates because of their usefulness in research and technology.Micelles are elongated,flexible aggregates formed by amphiphilic molecules spontaneously self-organizing in liquids.The nature of the surfactant determines its unique shape,which may be altered by mixing it with other substances or changing physicochemical variables like as temperature,pH,or salinity.The rheology of viscoelastic fluid systems is currently being modified using nanoparticles.This method,which was just introduced about 10 years ago,has shown to be highly promising,producing significant improvements in rheological properties,particularly at reservoir temperatures.The goal of this research is to investigate and assess the rheology of an aqueous cationic surfactant solution based on graphene oxide nanoparticles.The thermodynamics,structure and rheology of nanoparticle-based cationic surfactant solutions were investigated experimentally.According to structural and thermodynamic investigations in surfactant-nanoparticle mixtures,micellenanoparticle interactions arise as physical crosslinks between micelles.The existence of these interactions is shown to generate considerable viscosity and viscoelasticity in wormlike micelles,even when the fluid is Newtonian in the absence of nanoparticles.The viscosity,shear modulus and relaxation time all increase as particle concentration increases.Adding nanoparticles generates a network of micellar entanglements as a result of that.Our results demonstrate that adding nanoparticles to surfactant solutions provides for a one-of-a-kind method of altering fluid rheology under a range of circumstances.

Rheological behavior of mixed system of ionic liquid [C8mim]Br and sodium oleate in water

Abstract We report on the rheological behavior of wormlike micelles constructed by ionic liquid surfactant [Csmim]Br （1-octyl-3-methylimidazolium bromide） and anionic surfactant sodium oleate （NaOA） in aqueous solution. The effects of surfactant composition, total surfactant concentration, added salts, and temperature were investigated. The prevailing surfactant effect at lower concentration and the leading cosolvent effect at higher concentration of [Csmim]Br may be the main reasons for appearance of well-established maximum in key rheologi- cal parameters with variation of surfactant composition and total surfactant concentration. The Cole-Cole plots demon- strate that the systems （total surfactant concentration falls within 0.17-0.35 mol. L- 1 and molar ratio 0.33≤R ≤ 0.50） fit the Maxwell＇s mechanical model as linear viscoelastic fluid. The addition of NaBr or sodium salicylate decreases significantly the viscosity and the relaxation time of the wormlike micelle solution but cannot change the value of plateau modulus Go. The present system has low rheological tolerance to temperature. The increase of temperature decreases the average contour length and viscosity of wormlike micelles and thus strengthens the relaxation progress of diffusion and weakens the relaxation progress of reptation. Increasing the temperature also decreases the value of plateau modulus G0 and shifts the minimum value of the loss modulus G″min to higher frequencies.