Experimental study on adsorption of a new surfactant onto carbonate reservoir samples-application to EOR

Application of biosurfactants in enhanced oil recovery ex-situ: a review

With a growing focus on environmentally friendly solutions, biosurfactants derived from plants or microorganisms have gained attention for Enhanced Oil Recovery (EOR) applications. Biosurfactants offer several advantages over existing options, including biodegradability, low toxicity, availability of raw materials, resistance to harsh reservoir conditions, and improved water/oil interfacial tension reduction. Different organisms, such as bacteria, fungi, and plants, can produce these natural surfactants. Bacillus sp. and Pseudomonas sp. bacteria are extensively studied for their ability to produce biosurfactants using low-cost carbon and nitrogen sources, exhibiting excellent surface activity and low critical micellar concentration (CMC). Fungi, though less commonly used, can also produce biosurfactants, albeit with lower interfacial activity. Plant-derived natural surfactants find wide application in laboratory tests for EOR, despite having higher CMC. This review not only summarizes the current knowledge on biosurfactants but also offers a novel comparative analysis of those produced by bacteria, fungi, and plants, examining their CMC, surface tension, and interfacial tension properties. Additionally, it quantifies the number of publications on the use of biosurfactants for Microbial Enhanced Oil Recovery ex-situ (MEOR ex-situ) over the past 30 years and compares these with biosurfactants derived from plant sources. Our study is unique in its comparative approach and the quantification of literature on MEOR ex-situ. The findings reveal that biosurfactants produced by bacteria generally exhibit superior surface activity, even at lower concentrations, compared to those produced by plants or fungi. This new comparative perspective and thorough literature analysis highlight the distinctive contributions of this study. Overall, the use of biosurfactants for EOR represents a promising approach to cleaner energy production, with the potential to reduce environmental impact while improving oil recovery.

Investigation of ionic liquid adsorption and interfacial tension reduction using different crude oils; effects of salts, ionic liquid, and pH

The results revealed the significant effect of NaCl, KCl, CaCl2, MgCl2, CaSO4, MgSO4, and Na2SO4 and pH values of 3.5-11 on the interfacial tension (IFT) reduction using three types of neutral, acidic, and basic crude oils, especially for acidic crude oil (crude oil II) as the pH was changed from 3.5 to 11 (due to saponification process). The findings showed the highest impact of pH on the IFT of crude oil II with a reducing trend, especially for the pH 11 when no salts exist. The results revealed that the salts except MgCl2 and CaCl2 led to a similar IFT variation trend for the case of distilled water/crude oil II. For the MgCl2 and CaCl2 solutions, a shifting point for IFT values was inevitable. Besides, the dissolution of 1-dodecyl-3-methyl imidazolium chloride ([C12mim][Cl]) with a concentration of 100-1000 ppm eliminates the effect of pH on IFT which leads to a reducing trend for all the examined crude oils with minimum IFT of 0.08 mN/m. Finally, the [C12mim][Cl] adsorption (under pH values) for crude oils using only Na2SO4 was measured and the minimum adsorption of 0.41 mg surfactant/g Rock under the light of saponification process was obtained.

Orange Mesocarp Extract as a Natural Surfactant: Impact on Fluid-Fluid and Fluid-Rock Interactions during Chemical Flooding

Surfactant flooding has suffered a huge setback owing to its cost and the ecotoxic nature of synthetic surfactants. The potential of natural surfactants for enhanced oil recovery has attracted a great deal of research interest in recent times. In this research, orange mesocarp extract (OME) was studied as a potential green surface-active agent in recovering heavy oil. The extract obtained from the orange (Citrus sinensis) mesocarp using alkaline water as solvent was characterized by Fourier transform infrared spectrophotometry . Phase behavior was studied to ascertain its stability at 100 °C and compatibility with divalent ions. Microemulsion system, interfacial tension, optimal salinity, and critical micelle concentration were analyzed to evaluate the surfactant. Oil displacement analysis using an oil-wet sandstone medium under reservoir conditions was performed. Surfactant adsorption mechanism on the core was investigated at atmospheric conditions (28 °C) using the Langmuir, Freundlich, Temkin, and linear isotherm models, while the kinetics pattern was modeled with the pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models. Results showed fluid compatibility and bicontinuous microemulsion at varied temperatures. Surfactant flooding produced an additional oil recovery of 44 and 29.1%, which confirms the capability of this natural surfactant in recovering heavy oil. Langmuir isotherm gave the highest correlation coefficient (R2) value of 0.982, indicating that the adsorption of the surfactant (OME) on the core occurred at specific homogeneous sites, which when occupied by a higher surfactant concentration will disallow further adsorption on these sites. From the R2 values, almost all of the kinetic models corroborated good adsorption capacity of the core and an affinity for the surfactant at low concentration. This indicates that low concentration of the surfactant may not favor the enhanced oil recovery operation due to adsorption in the reservoirs, hence the need to flood at a higher surfactant concentration.

Can droplet size influence antibacterial activity in ultrasound-prepared essential oil nanoemulsions?

Essential oil nanoemulsion may have improved antibacterial properties over pure oil and can be used for food preservation. Ultrasonic cavitation is the most common mechanism for producing nanoemulsions, and the impact of processing parameters on droplet properties needs to be elucidated. A systematic literature search was performed in four databases (Science Direct, Web of Science, Scopus and PubMed), and 987 articles were found, 16 of which were eligible for the present study. A meta-analysis was performed to qualitatively assess which process parameters (power, sonication time, essential oil, and tween 80 concentration) can influence the final droplet size and polydispersity and how droplet size is associated with antibacterial activity. We observed that power, essential oil, and tween 80 concentrations added during processing are the critical variables for forming smaller droplets. Ratios of up to 3:1 (surfactant:oil) can produce droplets smaller than 180 nm with antibacterial properties superior to pure oil or isolated compounds. The improved properties of nanoemulsions are associated with the size and chemical composition of the droplet since the proportion of the hydrophobic core (EO) and the hydrophilic outer layer (Tween 80) directly influences the antibacterial mechanism of action.

Experimental Investigation of Foam Flooding Using Anionic and Nonionic Surfactants: A Screening Scenario to Assess the Effects of Salinity and pH on Foam Stability and Foam Height

Gravity override and viscous fingering are inevitable in gas flooding for improving hydrocarbon production from petroleum reservoirs. Foam is used to regulate gas mobility and consequently improve sweep efficiency. In the enhanced oil recovery process, when the foam is introduced into the reservoir and exposed to the initial saline water saturation and pH condition, selection of the stable foam is crucial. Salinity and pH tolerance of generated foams are a unique concern in high salinity and pH variable reservoirs. NaOH and HCl are used for adjusting the pH, and NaCl and CaCl₂ are utilized to change salinity. Through analyzing these two factors along with surfactant concentration, we have instituted a screening scenario to optimize the effects of salinity, pH, surfactant type, and concentration to generate the most stable state of the generated foams. An anionic (sodium dodecyl sulfate) and a nonionic (lauric alcohol ethoxylate-7) surfactants were utilized to investigate the effects of the surfactant type. The results were applied in a 40 cm synthetic porous media fully saturated with distilled water to illustrate their effects on water recovery at ambient conditions. This most stable foam along with eight different stabilities and foamabilities and air alone was injected into the sand pack. The results show that in optimum surfactant concentration, the stability of LA-7 was not highly changed with salinity alteration. Also, we probed that serious effects on foam stability are due to divalent salt and CaCl₂. Finally, we found the most water recovery that was obtained by the three most stable foams by the formula of 1 cmc SDS + 0.5 M NaCl, 1 cmc SDS + 0.01 M CaCl₂, and LA-7@ pH ∼ 6 from porous media flooding. Total water recovery for the most stable foam increased by an amount of 65% compared to the state of air alone. A good correlation between foam stability and foamability at higher foam stabilities was observed.

Development and Evaluation of Surfactant Nanocapsules for Chemical Enhanced Oil Recovery (EOR) Applications

The primary objective of this study is the synthesis of nanocapsules (NC) that allow the reduction of the adsorption process of surfactant over the porous media in enhanced oil recovery processes. Nanocapsules were synthesized through the nanoprecipitation method by encapsulating commercial surfactants Span 20 and Petro 50, and using type II resins isolated from vacuum residue as a shell. The NC were characterized using dynamic light scattering, transmission electron microscopy, Fourier transform infrared, solvency tests, softening point measurements and entrapment efficiency. The obtained NC showed spherical geometry with sizes of 71 and 120 nm for encapsulated Span 20 (NCS20), and Petro 50 surfactant (NCP50), respectively. Also, the NCS20 is composed of 90% of surfactant and 10% of type II resins, while the NCP50 material is 94% of surfactant and 6% of the shell. Nanofluids of nanocapsules dispersed in deionized water were prepared for evaluating the nanofluid—sandstone interaction from adsorption phenomena using a batch-mode method, contact angle measurements, and FTIR analysis. The results showed that NC adsorption was null at the different conditions of temperatures evaluated of 25, 50, and 70 °C, and stirring velocities up to 10,000 rpm. IFT measurements showed a reduction from 18 to 1.62 and 0.15 mN/m for the nanofluids with 10 mg/L of NCS20, and NCP50 materials, respectively. Displacements tests were conducted using a 20 °API crude oil in a quarter five-spot pattern micromodel and showed an additional oil recovery of 23% in comparison with that of waterflooding, with fewer pore volumes injected than when using a dissolved surfactant.

Oil-Water Interfacial Tensions of Silica Nanoparticle-Surfactant Formulations

The implementation of nanotechnology in all industries is one of most significant research fields. Nanoparticles have shown a promising application in subsurface fields. On the other hand, various surfactants have been used in the oil industry to reduce oil/water interfacial tension and also widely used to stabilize the nano-suspensions. The primary objective of this study was to investigate the improvements of surfactants ability in term of interfacial tension (γ) reduction utilizing addition of silicon dioxide nanoparticles at different temperatures and salinity. The pendant drop technique has been used to measure γ and electrical conductivity has been used to measure the critical micelle concentration (CMC). The synergistic effects of surfactant-nanoparticles, salt-nanoparticles, and surfactant-salt-nanoparticles on γ reduction and the critical micelle concentration of the surfactants have been investigated. Extensive series of experiments for γ and CMC measurements were performed. The optimum condition for each formulation is shown. We conclude that nanoparticles-surfactant can significantly reduce γ if correctly formulated.

Study on Cardanolbetaine Surfactants for Ultralow Interfacial Tension in a Low Range of Surfactant Concentration and Wide Range of Temperature Applied in Compound Flooding

Surfactant flooding aims at lowering the interfacial tensions between the oil and water phases to improve the displacement efficiency during oil recovery. However, ionic surfactants will lose their property in high temperature and high salt reservoirs. This investigation considers the cardanolbetaine surfactants as candidates for enhanced oil recovery (EOR) application in high temperature and high salt reservoirs. According to the experimental results, these surfactants can be effective in lowering interfacial tension (IFT) at dilute concentration, without requiring an alkaline or co-surfactants. In addition, these surfactants exhibit a low IFT at high salinity, high temperature and high concentration of divalent condition, the best surfactant concentration is 0.3 g L−1. The temperature resistance results show that it also has an excellent interfacial property at a wide range temperature from 35.0°C to 85.0°C, and remains its ultralow IFT (≤ 10−3 mN m−1) during 60 days at 85.0°C. The optimal concentration of salt tolerance is 50 g L−1 to 100 g L−1 of NaCl, 100 mg L−1 to 300 mg L−1 of Ca2+ respectively.