The Importance of Microemulsion for the Surfactant Injection Process in Enhanced Oil Recovery

Microemulsion is the main parameter that determines the performance of a surfactant injection system. According to Myers, there are four main mechanisms in the enhanced oil recovery (EOR) surfactant injection process, namely interface tension between oil and surfactant, emulsification, decreased interfacial tension and wettability. In the EOR process, the three-phase regions can be classified as type I, upper-phase emulsion, type II, lower-phase emulsion and type III, middle-phase microemulsion. In the middle-phase emulsion, some of the surfactant grains blend with part of the oil phase so that the interfacial tension in the area is reduced. The decrease in interface tension results in the oil being more mobile to produce. Thus, microemulsion is an important parameter in the enhanced oil recovery process.

Radial dynamics of an encapsulated microbubble with interface energy

In this work a mathematical model based on interface energy is proposed within the framework of surface continuum mechanics to study the dynamics of encapsulated bubbles. The interface model naturally induces a residual stress field into the bulk of the bubble, with possible expansion or shrinkage from a stress-free configuration to a natural equilibrium configuration. The significant influence of interface area strain and the coupled effect of stretch and curvature is observed in the numerical simulations based on constrained optimization. Due to the bending rigidity related to additional terms, the dynamic interface tension can become negative, but not due to the interface area strain. The coupled effect of interface strain and curvature term observed is new and plays a dominant role in the dominant compression behaviour of encapsulated bubbles observed in the experiments. The present model is validated by fitting the experimental data of $1.7\,\mathrm {\mu }$ m, $1.4\,\mathrm {\mu }$ m and $1\,\mathrm {\mu }$ m radii bubbles by calculating the optimized parameters. This work also highlights the role of interface parameters and natural configuration gas pressure in estimating the size-independent viscoelastic material properties of encapsulated bubbles with interesting future developments.

Effects of interactions in natural gas/water/rock system on hydrocarbon migration and accumulation

The study of natural gas accumulation process in tight formation has become the focus of the petroleum industry. One of the priorities is the effects of interactions in natural gas/water/rock system on hydrocarbon migration and accumulation process. On the macroscopic scale, we investigate the interactions in natural gas/water/rock system by formation fluorescence test and production data analysis. One the microscopic scale, the mechanisms are revealed by mathematical analysis and experimental methods considering the variation of geological temperature and pressure. The effects of interactions in natural gas/water/rock system are also simulated by numerical simulation. The results are visualized and quantified. A novel semi-analytical method based on a physical experiment is proposed to calculate the temperature- and pressure-dependent contact angle and interface tension which reflect the interactions in the natural gas–water–rock system. This semi-analytical is embedded in the numerical simulation during the simulation of the natural gas charging process. The results indicate that with the increase of geological temperature and pressure, the contact angle will increase and the interface tension between natural gas and water will decrease. The capillary resistance in the formation will be reduced. Since the decrease of capillary resistance, the natural gas can be charged into smaller pores, so that the actual charging threshold is lower than the one originally obtained under present reservoir conditions. After considering the temperature and pressure during the accumulation process, some sand bodies that were thought not to be charged may have natural gas accumulate.

Design Method of Equivalent Driving Waveform Based on Electrowetting Response Characteristics

As a new reflective display technology, electrowetting displays (EWDs) have many important characteristics, such as high reflectivity, low power consumption, and paper-like display. However, the contact angle hysteresis, which is the inconsistency between the advancing contact angle and the receding contact angle of oil droplet movement, seriously affects the response speed of EWDs in the driving process. According to the hysteresis phenomenon of contact angle in an oil switch motion with the action of interface tension, the brightness curve of EWDs in the process of pixel switching by different driving voltages was tested in this paper, and driving voltage was changed from 30 to 100 V at the same time. Then, in order to reduce the influence of the hysteresis effect, an equivalent driving waveform design method with overdriving voltage was proposed, and the overvoltage was set to 100 V according to the hysteresis effect and driving characteristic of EWDs. Experimental results showed that the response rising time of EWDs was reduced to 21 ms by using the proposed driving waveform, and the response performance of EWDs can be effectively improved.

Adsorption Properties of Hydrocarbon and Fluorocarbon Surfactants Ternary Mixture at the Water-Air Interface

Measurements were made of the surface tension of the aqueous solutions of p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethylene glycols) having 10 oxyethylene groups in the molecule (Triton X-100, TX100) and cetyltrimethylammonium bromide (CTAB) with Zonyl FSN-100 (FC6EO14, FC1) as well as with Zonyl FSO-100 (FC5EO10, FC2) ternary mixtures. The obtained results were compared to those provided by the Fainerman and Miller equation and to the values of the solution surface tension calculated, based on the contribution of a particular surfactant in the mixture to the reduction of water surface tension. The changes of the aqueous solution ternary surfactants mixture surface tension at the constant concentration of TX100 and CTAB mixture at which the water surface tension was reduced to 60 and 50 mN/m as a function of fluorocarbon surfactant concentration, were considered with regard to the composition of the mixed monolayer at the water-air interface. Next, this composition was applied for the calculation of the concentration of the particular surfactants in the monolayer using the Frumkin equation. On the other hand, the Gibbs surface excess concentration was determined only for the fluorocarbon surfactants. The tendency of the particular surfactants to adsorb at the water-air interface was discussed, based on the Gibbs standard free energy of adsorption which was determined using different methods. This energy was also deduced, based on the surfactant tail surface tension and tail-water interface tension.

Effect of Nanocellulose on Water-Oil Interfacial Tension

Interfacial tension is an important parameter in enhanced oil recovery (EOR). The interaction between water and oil phase is a determinant factor of the interfacial tension. The interfacial tension changes if another component is added to the water-oil system. This study investigates the effect of adding nanocellulose to the water-oil system. To determine the molecular interactions that occur, a molecular dynamics simulation was carried out using the GROMACS-2018 software. The simulation shows that addition of nanocellulose slightly decreases the water-oil interface tension. Further, based on the density profile, nanocellulose may act as an emulsifier due to its geometric position in the water-oil interface. This is similar to asphaltene, which is a natural emulsifier in crude oil. The nanocellulose performs better in the presence of 1% NaCl as compared to pure water.

Continuous sulfonation of hexadecylbenzene in a microreactor

Heavy alkyl benzene sulfonates are inexpensive surfactants that are extensively used as oil-displacing agents during tertiary oil recovery. Among these, C16–18 heavy alkyl benzene sulfonates possess an excellent ability to reduce the oil-water interface tension. In this study, hexadecylbenzene sulfonic acid (HBSA) was synthesised in a continuous stirred-tank microreactor using a continuous method with 1,2-dichloroethane (EDC) dilution. Post-sulfonation liquid SO3 solution was used as a sulfonating agent for hexadecylbenzene (HDB). The effects of reaction conditions, such as the SO3:HDB molar ratio, sulfonation temperature and sulfonation agent concentration, on the yield and purity of the product were investigated. Optimisation of the reaction process yielded high-quality HBSA samples with a purity exceeding 99 wt%. The continuous sulfonation process significantly enhanced the production and efficiency in the case of a considerably short residence time (10 s) in the reactor, without the need for aging. The results of this study demonstrate significant potential for application in industrial production.