Emulsification Tests Research Articles

Synergistic remediation of hydrocarbons using a hybrid approach: Harnessing biosurfactant and silver nanoparticles

A biosurfactant is an amphiphilic molecule that has both hydrophobic and hydrophilic properties. Biosurfactants from microbial sources with oil degradation potential were isolated from hydrocarbon-contaminated sites. Oil displacement and emulsification tests in this study identified the biosurfactant produced. The biosurfactants produced by the isolated bacteria possess anti-microbial properties. The cell-free supernatants of Bacillus subtilis and Pseudomonas aeruginosa showed positive results for the oil displacement method. The drop collapse test supported the biosurfactant production by these isolates. The synthesis of silver nanoparticles from Acalypha indica plant leaf extract was carried out. The biosurfactants (BS) and silver nanoparticles (AgNP) was also carried out. Their application as individual and synergistic effects in the bioremediation of hydrocarbons (engine waste oil) was discussed. Gravimetric analysis was used to analyse the degradation of engine oil. Silver nanoparticles showed absorbance in the range of 200 and 400 nm. Seven discrete peaks were obtained in FT-IR, representing the main functional group of AgNPs. The reduction of silver nitrate (AgNO3) into silver nanoparticles (AgNP) occurred due to the presence of biomolecules. The SEM analysis showed that the size of the nanoparticle is between 69 and 87 nm and is crystalline. The average distribution of the diameter of the silver nanoparticles was 186.9 nm. Broader peaks of XRD reflect the influence of the experimental circumstances on the nucleation and development of the crystal nuclei and indicate smaller particle sizes. The biosurfactants showed less degradation than the synergistic method employed with biosurfactants and silver nanoparticles. Therefore, it is concluded that the silver nanoparticles influenced the biosurfactant and increased the rate of degradation of the engine waste oil.

Interfacial rheological properties of pepsin-hydrolyzed lentil protein isolate at oil-water interfaces

Lentil protein isolate (LPI) was investigated for its potential as a plant protein-based emulsifier. LPI consists mainly of globulins with high molecular weights which are relatively slow to adsorb and stabilize oil-water interfaces. Smaller proteins, such as whey protein, can stabilize the interface much faster, quickly forming a viscoelastic film that slows down the rate of droplet recoalescence, leading to smaller droplets. To increase the rate of adsorption, LPI was enzymatically hydrolyzed by pepsin at 1.5% and 4.5% degree of hydrolysis (DH), to obtain small peptides. The behavior of these peptides was studied at the oil-water interface in comparison to whey protein isolate (WPI) and native lentil protein isolate (LPI). Interfacial properties were investigated using dilatational and interfacial shear rheology in the linear viscoelastic regime (LVE) and nonlinear viscoelastic regime (NLVE) and these were related to protein characteristics and emulsion formation. The 1.5% and 4.5%DH LPI showed high surface hydrophobicity, and consisted mainly of low molecular weight peptides, which contributed to faster adsorption kinetics and consequently covered the interface faster than LPI. In dilatation, the native and hydrolyzed LPI-stabilized interfaces had comparable stiffness and were clearly weaker than WPI-stabilized interfaces, which contrasts with the results in shear deformations, where the former both had higher stiffness than WPI. Both hydrolyzed LPI and WPI formed more brittle and less stretchable interfaces compared to native LPI in both dilatational and shear rheology. In emulsification tests, native LPI produces the largest droplets, and the 4.5% DH LPI and WPI have the smallest droplet size. But, bridging flocculation was observed when emulsions were prepared with both hydrolyzed LPI, which may be attributed to inter-droplet hydrophobic interactions between small polypeptides. This can be linked to an increase in the surface hydrophobicity of hydrolyzed LPI. Thus, the use of native LPI as a stabilizer in emulsion preparation is preferable over the hydrolyzed samples, despite its larger droplet size.

Extraction of biosurfactant from pseudomonas aeruginosa inhabiting oil-spilled soils

BackgroundScreening for biosurfactant-producing microbes involves the process of sampling and isolating bacteria from various environmental sources. Hydrocarbon-contaminated locations are considered ideal sources for isolating bacteria that produce biosurfactants. This is because these microbes have adapted to living in oil-contaminated environments and have developed mechanisms to produce biosurfactants as a means of survival. Therefore, screening microbes from such locations increases the likelihood of finding bacteria capable of producing biosurfactants.ResultsThis investigation aimed to isolate bisurfactant-producing bacteria from oil-contaminated soil samples, with a particular focus on Pseudomonas aeruginosa. Out of the 10 samples collected, four were confirmed to be P. aeruginosa, and all strains showed positive results for antagonistic, hemolytic, and emulsification tests. The strains were effective against B. subtilis, S. aureus, and E. coli but less effective against A. hydrophila. The PS10 strain exhibited the highest emulsification index, while PS08 showed the lowest. Based on microscopic and biochemical examination, P. aeruginosa was identified as the most effective isolate.ConclusionThese findings highlight the potential of P. aeruginosa as a biosurfactant producer for industrial and environmental applications. However, further studies are needed to fully understand the biosurfactant production potential of these strains and to optimize the conditions for biosurfactant production.

Isolation and Characterization of Biosurfactant Producing Pseudomonas aeruginosa YLA03 and its Diesel Degradation Potentials

This work was aimed at isolating and characterising biosurfactant producing bacteria strain from diesel oil contamination sites. The potential of the strain to degrade diesel oil n-alkanes was further studied. Soil samples were collected from diesel rich areas, and identified strains were grown on minimal media that contained diesel oil as only carbon source. Enrichment culture technique was used to identify bacteria. Seventeen bacteria strains were identified based on their capacity to use diesel oil as carbon source. Other qualitative screening methods were employed to determine the potential to produce biosurfactants. Isolate A03 was the only candidate that shows positive signs for drop collapse, foaming, haemolytic, oil displacement and emulsification tests. The effect of various culture parameters (incubation time, concentration of diesel, nitrogen source, pH and temperature) on biodegradation of diesel was evaluated. Optimum pH was 8.0 at 35° C, while the incubation time at maximum bacteria growth was five (5) days. The favourable diesel oil concentration was 7.5% for the isolate. The isolate has shown degradative ability towards dodecane, Tridecane, tetradecane but was unable to degrade 2, 6, 10-trimethyl- dodecane. It degraded between 10.09% - 45.39% of individual diesel alkanes. The strain has exhibited potential for degrading diesel alkanes and was identified as pseudomonas aeruginosa strain A3 (Accession Number: MZ027605) using the 16S rRNA. Sequencing.

Investigations on the enhanced oil recovery capacity of novel bio-based polymeric surfactants

Chemical enhanced oil recovery (cEOR) remains one of the most potent tertiary recovery methods. However, because of the complexity, cost, and environmental risks, attention is shifting towards bio-based polymeric surfactants as a possible alternative. Due to its vast abundance, cellulose has been identified as a source and cheap means of developing bio-based chemicals for oil recovery. In this study, novel hydrophobically modified cellulose sulphates, DPEA-Cell-OSO3−I (D-I) and DPEA-Cell-OSO3−II (D-II), were synthesized via microwave-assisted REDOX-mediated free-radical random copolymerization. Molecular characterization using nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) revealed their unique molecular features. In particular, D-II is identified as a mesoporous material. Rheological studies carried out on an economic concentration range of 50 to 1500 ppm showed that the novel products have moderate thickening properties, with viscosities less than 100 cP. Furthermore, it was discovered that the fluids are thermo-viscosifying and dilatant as well. Interfacial tension investigations revealed that they are surface-active with interfacial tension (IFT) lowering profiles improving with temperature as well, dropping down to the levels of 0.01 mN/m for D-I. They also demonstrated strong emulsifying capacity as Windsor types –II, +II, and middle phase microemulsion type III were produced during spontaneous emulsification tests. During coreflooding, D-I and D-II attained recoveries of 36 % and 53 %, respectively, over waterflood. D-II in particular had a very high residual resistant factor of 80, which is attributed to its dilatant nature, and emulsifying capabilities. In all, the properties and performances of the novel cellulose sulphate derivatives were linked to their molecular structures and architectures. Most importantly, these bio-based EOR materials will be suitable for high-temperature reservoirs.

Experimental study on wax removal and viscosity reduction of waxy crude oil by Ochrobactrumintermedium

To investigate the influence of microbial wax removal and viscosity reduction technologies on the fluidity of waxy crude oil, this study took the waxy crude oil from China's Daqing Oilfield as the experimental object for microbial wax removal and viscosity reduction experiment. First, utilizing standard strain screening and culture protocols, a high-efficiency microbial strain H-1 (Ochrobactrum intermedium) was proposed from in situ soil. The single factor experiment and multi-factor response surface analysis were then utilized to optimize the temperature, initial pH value of the medium, and NaCl mass concentration needed for the strain's growth. Oil displaced activity and emulsification tests were used to evaluate the biosurfactants produced by the metabolism of strain H-1, and Fourier transform infrared spectroscopy was used to identify the types of biosurfactants. Finally, the application effect of strain H-1 on wax removal and viscosity reduction of waxy crude oil were clarified through the wax crystal morphology, wax content, and viscosity of waxy crude oil. The research findings indicated that strain H-1 produced best at a temperature of 38.5 °C, pH value was 7.1 and the mass fraction of NaCl was 0.64%. The lipopeptide biosurfactant produced by strain H-1 can displace oil. Additionally, strain H-1 has a high emulsifying capacity, with a 61.25% emulsifying coefficient. After 7 days of treatment with the strain H-1, the wax crystal morphology of the waxy crude oil changed from a large-sized aggregated to a small-sized sparse condition, and the wax content of the waxy crude oil fell by 38.67%. The viscosity reduction rate of strain H-1 to waxy crude oil was consistently greater than 30% over the temperature range of 30–42 °C, with the greatest rate of 42.38% at 39 °C. The preceding results demonstrate that strain H-1 can degrade the wax components of waxy crude oil, lower the crude oil's low temperature viscosity, and then improve the crude oil's low-temperature fluidity.

The oil/water interfacial behavior of microgels used for enhancing oil recovery: A comparative study on microgel powder and microgel emulsion

Microscale crosslinked polymeric hydrogels, termed microgels, have attracted considerable attention as enhancing oil recovery (EOR) agents due to their favorable in-depth fluid diversion effect. However, the oil/water interfacial behavior of microgels remains unclear, limiting the comprehensive understanding of the EOR mechanism. In this study, the oil/water interfacial behavior of microgel powder (MP) and microgel emulsion (ME) was studied through emulsification tests and interfacial tension (IFT) measurements. Despite the similar properties of the microgel particles, such as morphology, size distribution and zeta potential, ME exhibited better emulsification performance than MP in deionized (DI) water due to the presence of additional surfactants in ME. However, since the competitive adsorption between the microgel particles and surfactants on the oil/water interface changed with salinity, ME exhibited a higher emulsion volume but lower emulsion stability than MP in brine. Moreover, W/O and O/W emulsions were formed in DI water, but only an O/W emulsion was formed in brine for ME. Furthermore, MP exhibited better IFT reduction performance in brine due to the weaker steric hindrance and tighter adsorption layer on the oil/water interface. In contrast, ME showed better IFT reduction performance in DI water owing to the interaction between the microgel particles and the surfactants. Considering that MP is usually used in the laboratory while commercial microgels are provided in the form of ME, the different oil/water interfacial behaviors of MP and ME may result in an inconsistent understanding of the EOR mechanism in laboratory study and field application.

Design and validation of an expeditious analytical method to quantify the emulsifying activity during biosurfactants/bioemulsifiers production

Biosurfactants (BS) and bioemulsifiers (BE) are amphiphilic molecules that are produced by a wide range of microorganisms. Although the chemical composition of BS and BE is different, both BS/BE have recognized emulsifying properties, which are the focus of this study. Herein, a rapid and simple analytical method to quantify the emulsifying activity (EA) of a product produced by the actinomycete Gordonia alkanivorans strain 1B (BS/BE), which exhibits emulsifying properties, was developed. The analytical approach was based on the ability of a BS/BE solution to form a stable emulsion when mixed with n-heptane. So, using 4 mL screw cap glass tubes (10 × 75 mm, ND10 caps with PTFE septum), the EA was assessed by adding 1 mL of n-heptane to 1 mL of an aqueous solution containing the test product, mix by vortexing at high speed (2 min) and place the tube in an upright stable position for 10 min before analyzing. A set of emulsification tests with increasing volumes of test product solutions was carried out until 100% emulsion was obtained in the organic phase. One emulsification unit was defined as the minimum volume of product (Volmin of emulsifier/surfactant, up to 1 mL) needed to form and maintain 100% emulsion in the organic phase. The corresponding emulsifying activity value is presented in U/mL, and it is calculated as: EA (product) = 1 U/Volmin (mL). Further validation by testing several synthetic surfactants and industrial/domestic dishwashing detergents, in parallel with the bacterial crude BS/BE, towards emulsifying activity determination (U/mL) was performed demonstrating the wide range of the method applicability. Moreover, the specific emulsifying activity for each product tested was estimated though correlation analysis (linear regression) between volumetric emulsifying activity (U/mL) and product concentration (g/L). Indeed, this new analytical approach to quantify the emulsifying activity is accurate and reproducible, and consequently it can be a promising tool to apply in screening/monitorization studies on BS/BE production enabling reliable comparisons.

Oxidizing emulsifiers: Gelators for water in hydrocarbon reactive emulsions

Oxidizing emulsifiers were produced using calcium peroxide and polysaccharides extracted from edible mushrooms. The polysacchardes were mainly glucans, as indicated by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Our study investigates the potential application of these oxidizing emulsifiers to remediate and immobilize spills of a model hydrocarbon (toluene) in groundwater. Interfacial tension measurements showed that the oxidizing emulsifiers adsorbed at toluene-water interfaces, producing rigid interfacial films (as demonstrated through Langmuir trough experiments). The oxidizing emulsifiers were particle-like, as observed with scanning electron microscopy (SEM). Emulsification tests and optical microscopy observations showed that the oxidizing emulsifiers stabilized water in toluene emulsions, hence promoting contact between the emulsifying oxidizers and toluene. Therefore, toluene degradation was greater with the oxidizing emulsifiers than with calcium peroxide (used at the same concentrations), as demonstrated through gas chromatography-mass spectroscopy (GC-MS) experiments. Shear rheology tests showed that the water in toluene emulsions stabilized by the oxidizing emulsifiers were gel-like. The gelation of hydrocarbon spills would be useful to immobilize hydrocarbon spills during their remediation, thereby impeding their unwanted migration. Our study describes for the first-time emulsifying oxidizers, which have the potential to enhance the remediation of hydrocarbon spills (compared to traditional oxidizers), while safely immobilizing them.

The Role of Endogenous Proteins on the Emulsification of Silicone Oils Used in Vitreoretinal Surgery

The present work is aimed at investigating the chemicophysical properties of the interface between silicone oils (SOs) used in vitreoretinal surgery and aqueous solutions, in the presence of surfactant biomolecules. Such molecules are thought to play an important role in the formation of SO emulsions in vitrectomised eyes, in which the natural vitreous body has been replaced with a SO. In particular, we have measured the interfacial tension (IT) and the interfacial dilational viscoelasticity (DV) of the interface between SO (Siluron 1000) and serum proteins (albumin and γ-globulins) at various concentrations in a Dulbecco alkaline buffer. The equilibrium IT value is relevant for the onset of emulsification, and the DV influences the stability of an emulsion, once formed. The study is complemented by preliminary emulsification tests. The experimental results show that, when proteins are dissolved in the aqueous solution, the rheological properties of the interface change. The IT decreases significantly for physiological protein concentrations, and the DV modulus achieves high values, even for small protein concentrations. The emulsification tests confirm that, in the presence of proteins, emulsions are stable on the time scale of months. We conclude that the measured values of IT in the presence of serum proteins are compatible with the promotion of droplet formation, which, in addition, are expected to be stable against coalescence. Adsorption of biomolecules at the interface with the SO is, therefore, likely to play an important role in the generation of an emulsion in eyes subjected to vitrectomy. These findings are relevant to identify strategies to avoid or control the formation of emulsions in eyes.

Intranasal Tadalafil nanoemulsions: formulation, characterization and pharmacodynamic evaluation

This study aims at improving the bioavailability of a poorly soluble phosphodiesterase-5 inhibitor; tadalafil (TD) via developing intranasal (IN) nanoemulsions (NEs). Optimum NE ingredients were selected based on solubility studies, emulsification tests, and phase diagram construction. Both o/w and w/o NEs were selected based on their drug loading capacity. Optimum formulations were subjected to physicochemical characterization and were assessed for nasal toxicity through biochemical analysis of tumor necrosis factor-α (TNF-α) and caspase-3 in rat nasal tissues. Pharmacodynamic study was performed via biochemical analysis of cyclic guanosine monophosphate (cGMP) in rat penis 2-h post-treatment and compared with oral suspension of Cialis® tablets. Optimum o/w and w/o NEs were successfully prepared using different ratios of Capmul-MCM-EP, Labrasol:Transcutol-HP (1:1) and water. Optimized formulations exhibited more than 4000-fold increase in TD solubility compared with its aqueous solubility. Both formulations were optically isotropic with the majority of globules in the nanometric-size range. Nasal toxicity study revealed no significant difference in values of TNF-α and caspase-3 between the NE-treated groups and the control group. Both TD-NEs succeeded to achieve a significant enhancement in cGMP levels. Our findings suggested that IN administration of the developed TD-NEs could provide a safe and effective alternative to TD oral delivery.

Relative permeability measurement in carbonate rocks, the effects of conventional surfactants vs. Ionic liquid-based surfactants

In the present study, the effect of two different kinds of surfactants namely conventional (Sodium dodecyl benzene sulfonate (SDBS)) and ionic liquid (IL)-based surfactants are investigated on the tertiary oil recovery using relative permeability concept. In this way, besides the Amott wettability index measurement, unsteady state core flooding tests are performed to not only find the effect of surfactant injection on tertiary oil recovery, but also to investigate their effects on relative permeability of carbonate rocks. In addition, for more reliable conclusions regarding the possible mechanisms, interfacial tension (IFT), compatibility and emulsification tests are carried out as a function of concentration. According to the results obtained through the core flooding experiments, it can be concluded that the injection of SDBS which substantially reduces the IFT value leads to higher tertiary oil recovery (26% based on original oil in place (OOIP)) although the ILs revealed more compatibility at the presence of harsh salinity conditions at any examined IL concentration in this study. Finally, the results obtained by plotting the relative permeability data and mining into the cross points one can conclude that in the case of using ILs, the active mechanisms during the tertiary oil recovery is dominantly related to wettability alteration mechanism while in the case of SDBS, the IFT reduction is the active mechanism.

Effect of amylose content in morphological, functional and emulsification properties of OSA modified corn starch

Octenyl succinic starch esters were prepared from three corn starches with different amylose content; namely, waxy (5.43%), normal (25.16%) and Hylon VII (65.84%). The degree of substitution varies from 0.0103 for waxy starch to 0.0125 for Hylon VII, meaning that the degree of substitution is positively correlated with the amylose content. Scanning electron microscopy images showed that the esterification reaction affected only the granule surface while leaving the integrity of the granules. Solubility and water retention capacity were increased with the OSA modification, with the effect more pronounced for higher amylose contents. X-ray analysis revealed that the crystallinity type was not affected by esterification. FTIR analysis corroborated the changes in the hydrated and ordered structures of starch granules. Emulsification tests showed that octenyl succinic starch ester was an effective emulsifier for stabilization of oil-in-water emulsions. In particular waxy and Hylon VII starches induced high stabilization degrees as revealed by long-term stability of oil-in-water emulsions.

Application of Bacillus subtilis strain for microbial-enhanced oil recovery

ABSTRACTIn order to improve the oil recovery, injection of exogenous bacteria into the oil reservoir is one of the most widely used microbial flooding methods. In this study, a screened strain of Bacillus subtilis (B. subtilis) was introduced to perform the microbial flooding. The biosurfactants produced by B. subtilis was one kind of cyclic lipopeptides, which could reduce the surface tension of the culture solution from 68 mN/m to 25 mN/m and also decrease the interfacial tension of water/oil from 25.6 to 4.6 mN/m. Emulsification tests indicated that the strain and the biosurfactants could degrade and emulsify the crude oil. In the oil displacement experiments, oil recovery was increased by 32.4% by injecting fermentation broth into the simulated formation. By respectively performing the emulsification and oil displacement tests, it was demonstrated that the biosurfactants and degradation of the microbes in the heavy components of the crude oil are the main factors to enhance the oil recovery. Besides, the optimal cultural temperature for strain of B. subtilis was set as 40°C. Nevertheless, the strain was inappropriate for the oil displacement under acidic conditions. In addition, the hydrophilic sands and an optimal culture solution volume of 0.7 pore volume (PV) would be in favor of the oil recovery. It was further confirmed that the efficiency of microbial flooding was much higher than that of the chemical oil displacement.

Strategic approach to developing a self-microemulsifying drug delivery system to enhance antiplatelet activity and bioavailability of ticagrelor.

BackgroundTicagrelor (TCG) is used to inhibit platelet aggregation in patients with acute coronary syndrome, but its poor solubility and low bioavailability limit its in vivo efficacy. The purpose of this study was to manufacture an optimized TCG-loaded self-microemulsifying drug delivery system (SMEDDS) to enhance the oral bioavailability and antiplatelet activity of TCG.Materials and methodsSolubility and emulsification tests were conducted to determine the most suitable oils, surfactants, and cosurfactants. Scheffé’s mixture design was applied to optimize the percentage of each component applied in the SMEDDS formulation to achieve optimal physical characteristics, ie, high solubility of TCG in SMEDDS, small droplet size, low precipitation, and high transmittance.ResultsThe optimized TCG-loaded SMEDDS (TCG-SM) formulation composed of 10.0% Capmul MCM (oil), 53.8% Cremophor EL (surfactant), and 36.2% Transcutol P (cosurfactant) significantly improving the dissolution of TCG in various media compared with TCG in Brilinta® (commercial product). TCG-SM exhibited higher cellular uptake and permeability in Caco-2 cells than raw TCG suspension. In pharmacokinetic studies in rats, TCG-SM exhibited higher oral bioavailability with 5.7 and 6.4 times higher area under the concentration–time curve and maximum plasma concentration, respectively, than a raw TCG suspension. Antiplatelet activity studies exhibited that the TCG-SM formulation showed significantly improved inhibition of platelet aggregation compared with raw TCG at the same dose of TCG. And, a 10 mg/kg dose of raw TCG suspension and a 5 mg/kg dose of TCG-SM had a similar area under the inhibitory curve (907.0%±408.8% and 907.8%±200.5%⋅hours, respectively) for antiplatelet activity.ConclusionThese results suggest that the developed TCG-SM could be successfully used as an efficient method to achieve the enhanced antiplatelet activity and bioavailability of TCG.

EVALUATION OF DIFFERENT SCREENING METHODS FOR BIOSURFACTANT PRODUCERS ISOLATED FROM EGYPTIAN FRESH WATER SAMPLES CONTAMINATED BY OIL SPILLS USING BACILLUS SUBTILIS AND BACILLUS LICHENIFORMIS

In all countries, oil exploration and use threatens the health of the environment and living creatures including humans. An oil spill is the release of petroleum hydrocarbon into the environment. One of the most applicable and safe method is the bioremediation treatment, using microorganisms .This work aims at treating oil spills in fresh water and to compile information on types and properties of biosurfactant. It also describes factors affecting these biosufactants production. Different screening methods e.g. oil spreading assay, Emulsification index (E24), Drop collapse assay, Blood agar test, Hemolysis, MaCconkey agar test were tested. Two isolates gave highly Emulsification tests named O3, O11, which were identified as Bacillus subtilis and Bacillus licheniformis respectively, were isolated from petroleum hydrocarbon contaminated water. Optimization of two isolates were done and highest biosurfactant activity at temperature ranges from 10 oC to 50 oC and pH ranges from 3 to 10 and salinity ranges from 0%to 30%. Also, the biosurfactant was characterized by Fourier transform infrared spectroscopy (FTIR) and surface tension measurement. FTIR showed the production of biosurfactant from Bacillus subtilis similar to surfactin, while the biosurfactant from Bacillus licheniformis similar to lichenysins. The use of microbial biosurfactants significantly decreases the hydrophobicity and increases the rate of hydrocarbon biodegradation. Biosurfactants obtain demonstrated good surface tension reduction capacity by Bacillus subtilis and Bacillus licheniformis up to 30 and 36Nm/m and have emulsifying activity 71% and 65% respectively.

Experimental study on the effect of interfacial tension on the conformance control of oil-in-water emulsions in heterogeneous oil sands reservoirs

Reservoir heterogeneity is a serious problem for many mature oilfields. Due to heterogeneity, much of the displacing fluid may flow into the high permeability zones in the formation, leaving most of the low permeability areas un-swept, which leads to high water production and low oil recovery. In this work, oil-in-water (O/W) emulsions were used as conformance control agents to reduce fluid flow of the high permeability zones in heterogeneous oil sands reservoirs. As well, for the first time, interfacial tension (IFT) effect on emulsion conformance control performance was studied. Emulsification tests were first performed to screen suitable emulsifiers which could be used to prepare stable O/W emulsions with different IFTs. Physiochemical properties of the emulsions were investigated by characterization tests in terms of their stability behavior, droplet size distribution and rheological properties.A series of heterogeneous parallel, dual-sandpack flow experiments were carried out to evaluate the profile control ability of emulsions with different IFTs of 0.04, 0.15, 0.92 and 5.20 mN/m in heterogeneous oil sands reservoirs. The results show that for the dual-sandpack models used in this study, emulsion conformance control performance gets better as IFT decreases from 5.20 mN/m to 0.15 mN/m, but it becomes worse as IFT further decreases to 0.04 mN/m. The fractional flow of the heterogeneous dual-sandpack diverts only once when flooded by an emulsion with an IFT of 5.20 mN/m. Emulsion with an IFT of 0.92 mN/m causes several flow diversions in the emulsion injection process, but the profile control ability could be destroyed by the flood of water. Emulsion with an IFT of 0.15 mN/m has good conformance control performance both at the emulsion flooding and subsequent water flooding stages, while emulsion with the least IFT of 0.04 mN/m shows very little profile control effect. The effect of emulsion slug size and sandpack permeability ratio on emulsion conformance control ability are also discussed in this paper.

Verbascum nigrum L. (mullein) extract as a natural emulsifier

Flowers of Verbascum nigrum L. (mullein) contain considering amounts of saponins which are surfactants with carbohydrates chain in their molecules. Hence, the mullein was used for water-oil (W/O) systems as an emulsion stabilizer. As an oil phase paraffin, rapeseed and Vaseline oils were used respectively. Emulsification and foaming tests were performed to evaluate stability of the emulsion system. Emulsification indexes (EI) were obtained after 24 h of W/O phases mixing. Moreover, EI indexes were determined after 8 weeks (E8w) of emulsions storage at room temperature. The impact of the plant extract particles size was evaluated too. Dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) techniques were used for the hydrodynamic diameter (dH) measurements (average values of dH were 133 nm and 92 nm for DLS and NTA analysis respectively). Raman spectra of mullein extracts and zeta potential (ζ = −43.3 mV) were measured and compared with another selected saponins plant extract. The emulsification tests showed that the emulsion stability increased with the decreasing size of the surfactant (mullein) hydrodynamic diameter. The best stability of the investigated O/W emulsion was shown for Vaseline oil system. Moreover, high impact on the surfactant properties of V. nigrum L. has the particle size. The O/W emulsions stabilized by filtrated extract nanoparticles exhibit longer stability than crude extract. The surface properties and nanostructures size proved that mullein extracts can be considered as a potential stabilizer for hydrocolloid systems and dedicated for food industry.

Mechanistic studies of enhanced oil recovery by imidazolium-based ionic liquids as novel surfactants

Ionic liquids are recently considered as an alternation to surfactants for their application in enhanced oil recovery (EOR) because of their promising surface-active properties. In the present study, the ability of a series of synthesized ionic liquids (C8mimBF4, C10mimBF4 and C12mimBF4) to reduce interfacial tension (IFT) and change the wettability of oil-wet rock have been investigated. Results demonstrated that all three synthesized ionic liquids enhanced interfacial properties and rock-wetting characteristics. The ionic liquids were able to significantly reduce IFT and remained stable at high temperature and saline conditions. Addition of organic alkali also showed a synergistic effect on IFT reduction between crude oil and ionic liquid solution. FTIR and zeta potential measurements were conducted to establish the mechanism of wettability alteration of oil-wet rock. Emulsification tests confirmed the capability of the ionic liquids to emulsify the trapped oil, which is an important mechanism of chemical EOR. The loss of ionic liquids by adsorption on rock surface was studied, and the adsorption data were analyzed by Langmuir and Freundlich models. Microemulsion study showed Winsor type III behavior with ultra-low IFT, which is beneficial for EOR application. Sand pack flooding experiments were conducted to study the EOR efficiency using the synthesized ionic liquids and around 32.28% additional recovery was observed after the conventional water flooding with injection of ionic liquid, polymer and alkali slugs.

Emulsification of heavy crude oil in brine and its plugging performance in porous media

In this paper, heavy crude oil and formation brine collected from Xinjiang oilfield were used to prepare crude oil-in-water (O/W) emulsions. Emulsification tests were first conducted to screen suitable emulsifiers. Then stability test, droplet size distribution analysis, and rheological property measurements were carried out to investigate the physicochemical characteristics of the developed O/W emulsions. It was found that surfactants of Span 60 and Tween 80 combined with sodium hydroxide could reduce the oil/water interfacial tension and thereby emulsify the heavy crude oil in formation brine. A series of sandpack flow tests were conducted to evaluate the plugging performance of the heavy O/W emulsions, emulsified using 0.1 wt% Span 60–0.1 wt% Tween 80–0.025 wt% NaOH. The flow test results showed that heavy O/W emulsion can result in more than 99% permeability reductions in sandpacks. The permeability reduction by emulsion plugging increased greatly with an increase in oil quality and injected emulsion slug, but decreased with an increase in sandpack permeability and injection flow rate.