Surfactants And Interfacial Phenomena

Surfactant flooding is an important technique used in enhanced oil recovery to reduce the amount of oil in pore space of matrix rock. Surfactants are injected to mobilize residual oil by lowering the interfacial tension between oil and water and/or by the wettability alteration from oil-wet to water-wet. A large number of cationic, anionic, non-ionic, and amphoteric surfactants have been investigated on a laboratory scale under different conditions of temperature and salinity. Selection of the appropriate surfactant is a challenging task, and surfactants have to be evaluated by a series of screening techniques. Different types of surfactants along with their limitations are reviewed with particular emphasis on the phase behavior, adsorption, interfacial tension, and structure–property relationship. Factors affecting the phase behavior, interfacial tension, and wettability alteration are also discussed. Field applications of surfactants for chemical enhanced oil recovery in carbonate and sandstone reservoi...

Review on Surfactant Flooding: Phase Behavior, Retention, IFT, and Field Applications

Surfactant-free oil-in-water emulsions prepared with temperature and pH sensitive poly(N-isopropylacrylamide)(PNIPAM) microgel particles offer unprecedented control of emulsion stability.

https://absimage.aps.org/image/MAR06/MWS_MAR06-2005-004393.pdf

Novel emulsions stabilized by pH and temperature sensitive microgels

With the ever increasing demand for energy to meet the needs of growth in population and improvement in the living standards in particular in developing countries, the abundant unconventional oil reserves (about 70% of total world oil), such as heavy oil, oil/tar sands and shale oil, are playing an increasingly important role in securing global energy supply. Compared with the conventional reserves unconventional oil reserves are characterized by extremely high viscosity and density, combined with complex chemistry. As a result, petroleum production from unconventional oil reserves is much more difficult and costly with more serious environmental impacts. As a key underpinning science, understanding the interfacial phenomena involved in unconventional petroleum production, such as oil liberation from host rocks, oil–water emulsions and demulsification, is critical for developing novel processes to improve oil production while reducing GHG emission and other environmental impacts at a lower operating cost. In the past decade, significant efforts and advances have been made in applying the principles of interfacial sciences to better understand complex unconventional oil-systems, while many environmental and production challenges remain. In this critical review, the recent research findings and progress in the interfacial sciences related to unconventional petroleum production are critically reviewed. In particular, the chemistry of unconventional oils, liberation mechanisms of oil from host rocks and mechanisms of emulsion stability and destabilization in unconventional oil production systems are discussed in detail. This review also seeks to summarize the current state-of-the-art characterization techniques and brings forward the challenges and opportunities for future research in this important field of physical chemistry and petroleum.

Interfacial sciences in unconventional petroleum production: from fundamentals to applications

Gemini surfactants are a group of novel surfactants with more than one hydrophilic head group and hydrophobic tail group linked by a spacer at or near the head groups. Unique properties of gemini surfactants, such as low critical micelle
 concentration, good water solubility, unusual micelle structures and aggregation behavior, high efficiency in reducing oil/water interfacial tension, and interesting rheological properties have attracted the attention of academic researchers and field experts. Rheological characterization and determination of the interfacial tension are two of the most important screening techniques for the evaluation and selection of chemicals for enhanced oil recovery (EOR). This review deals with rheology, wettability alteration, adsorption and interfacial properties of gemini surfactants and various factors affecting their performance. The review highlights the current research activities on the application of gemini surfactants in EOR.

A Review of Gemini Surfactants: Potential Application in Enhanced Oil Recovery

Novel oil-in-water (O/W) emulsions are prepared which are stabilised by a cationic surfactant in combination with similarly charged alumina nanoparticles at concentrations as low as 10-5  m and 10-4  wt %, respectively. The surfactant molecules adsorb at the oil-water interface to reduce the interfacial tension and endow droplets with charge ensuring electrical repulsion between them, whereas the charged particles are dispersed in the aqueous films between droplets retaining thick lamellae, reducing water drainage and hindering flocculation and coalescence of droplets. This stabilization mechanism is universal as it occurs with different oils (alkanes, aromatic hydrocarbons and triglycerides) and in mixtures of anionic surfactant and negatively charged nanoparticles. Further, such emulsions can be switched between stable and unstable by addition of an equimolar amount of oppositely charged surfactant which forms ion pairs with the original surfactant destroying the repulsion between droplets.

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Novel Oil‐in‐Water Emulsions Stabilised by Ionic Surfactant and Similarly Charged Nanoparticles at Very Low Concentrations

We put forward a simple protocol to prepare thermoresponsive Pickering emulsions. Using hydrophilic silica nanoparticles in combination with a low concentration of alkyl polyoxyethylene monododecyl ether (C12En) nonionic surfactant as emulsifier, oil-in-water (o/w) emulsions can be obtained, which are stable at room temperature but demulsified at elevated temperature. The stabilization can be restored once the separated mixture is cooled and rehomogenized, and this stabilization–destabilization behavior can be cycled many times. It is found that the adsorption of nonionic surfactant at the silica nanoparticle–water interface via hydrogen bonding between the oxygen atoms in the polyoxyethylene headgroup and the SiOH groups on particle surfaces at low temperature is responsible for the in situ hydrophobization of the particles rendering them surface-active. Dehydrophobization can be achieved at elevated temperature due to weakening or loss of this hydrogen bonding. The time required for demulsification decr...

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Thermoresponsive Pickering Emulsions Stabilized by Silica Nanoparticles in Combination with Alkyl Polyoxyethylene Ether Nonionic Surfactant.

Enhanced crude oil recovery by chemical flooding has been a main measure for postponing the overall decline of crude oil output in China, and surfactant-polymer (SP) flooding may replace alkali-surfactant-polymer flooding in the future for avoiding the undesired effects of using alkali. In this paper the synthesis of a surfactant with a large hydrophobe, didodecylmethylcarboxyl betaine (diC12B), and its adaptability in SP flooding were investigated. The results show that diC12B can be synthesized by reaction of didodecylmethyl amine, a product commercially available, with chloroacetic acid in the presence of NaOH, with a resulting yield as high as 80 wt% under appropriate conditions. With double dodecyl chain diC12B is highly surface active as displayed by its low CMC, 3.7 × 10−6 mol L−1, low γCMC, 27 mNm−1, as well as high adsorption and small cross section area (≤0.25 nm2) at both air/water and oil/water interfaces at 25 °C. By mixing with conventional hydrophilic surfactants diC12B can be well dissolved in Daqing connate water and reduce the Daqing crude oil/connate water interfacial tension to about 10−3 mN m−1 at 45 °C in a wide total surfactant concentration range, from 0.01 to 0.5 wt%. And a tertiary oil recovery, 18 ± 1.5 % OOIP, can been achieved by SP flooding using natural cores without adding any alkaline agent or neutral electrolyte. DiC12B seems thus to be a good surfactant for enhanced oil recovery by SP flooding.

Synthesis of Didodecylmethylcarboxyl Betaine and Its Application in Surfactant–Polymer Flooding

Innovation in the structure of surfactants is crucial to the construction of a surfactant-based system with intriguing properties. With dehydroabietic acid as a starting material, a nearly totally rigid azobenzene surfactant (R-azo-Na) was synthesized. The trans-R-azo-Na formed stable foams with half-lives of 636, 656, 976, and 872 min for 0.3, 1, 2, and 4 mmol·L–1 aqueous solutions, respectively. Under UV light irradiation, a fast collapse of the foams was observed, showing an in situ response. The excellent foam stability of trans-R-azo-Na leads to the extremely high photoresponsive efficiency. As revealed by dynamic surface tension and pulsed-field gradient NMR methods, an obvious energy barrier existed in the adsorption/desorption process of trans-R-azo-Na on the air/water interface. The foams formed by trans-R-azo-Na are thus stable against coarsening processes. The results reveal the unique photoresponsive behavior of a surfactant with a rigid hydrophobic skeleton and provide new insights into the s...

Photoresponsive Foams Generated by a Rigid Surfactant Derived from Dehydroabietic Acid

In the recent past, switchable surfactants and switchable/stimulus-responsive surface-active particles have been of great interest. Both can be transformed between surface-active and surface-inactive states via several triggers, making them recoverable and reusable afterward. However, the synthesis of these materials is complicated. In this paper we report a facile protocol to obtain responsive surface-active nanoparticles and their use in preparing responsive particle-stabilized foams. Hydrophilic silica nanoparticles are initially hydrophobized in situ with a trace amount of a conventional cationic surfactant in water, rendering them surface-active such that they stabilize aqueous foams. The latter can then be destabilized by adding equal moles of an anionic surfactant, and restabilized by adding another trace amount of the cationic surfactant followed by shaking. The stabilization-destabilization of the foams can be cycled many times at room temperature. The trigger is the stronger electrostatic interaction between the oppositely charged surfactants than that between the cationic surfactant and the negatively charged particles. The added anionic surfactant tends to form ion pairs with the cationic surfactant, leading to desorption of the latter from particle surfaces and dehydrophobization of the particles. Upon addition of another trace amount of cationic surfactant, the particles are rehydrophobized in situ and can then stabilize foams again. This principle makes it possible to obtain responsive surface-active particles using commercially available inorganic nanoparticles and conventional surfactants.

Xiaomei Pei

Papers

Novel Oil‐in‐Water Emulsions Stabilised by Ionic Surfactant and Similarly Charged Nanoparticles at Very Low Concentrations

Thermoresponsive Pickering Emulsions Stabilized by Silica Nanoparticles in Combination with Alkyl Polyoxyethylene Ether Nonionic Surfactant.

Synthesis of Didodecylmethylcarboxyl Betaine and Its Application in Surfactant–Polymer Flooding

Photoresponsive Foams Generated by a Rigid Surfactant Derived from Dehydroabietic Acid

Responsive Aqueous Foams Stabilized by Silica Nanoparticles Hydrophobized in Situ with a Conventional Surfactant