Oil-water Interface

Some aspects of the interfacial behavior of cellulose dissolved in an aqueous solvent were investigated. Cellulose was found to significantly decrease the interfacial tension (IFT) between paraffin oil and 85 wt% phosphoric acid aqueous solutions. This decrease was similar in magnitude to that displayed by non-ionic cellulose derivatives. Cellulose's interfacial activity indicated a significant amphiphilic character and that the interfacial activity of cellulose derivatives is not only related to the derivatization but inherent in the cellulose backbone. This finding suggests that cellulose would have the ability of stabilizing dispersions, like oil-in-water emulsions in a similar way as a large number of cellulose derivatives. In its molecularly dissolved state, cellulose proved to be able to stabilize emulsions of paraffin in the polar solvent on a short-term. However, long-term stability against drop-coalescence was possible to achieve by a slight change in the amphiphilicity of cellulose, effected by a slight increase in pH. These emulsions exhibited excellent stability against coalescence/oiling-off over a period of one year. Ageing of the cellulose solution before emulsification (resulting in molecular weight reduction) was found to favour the creation of smaller droplets.

Solvation can substantially modify the adsorption properties of heterogeneous catalysts. Although essential for achieving realistic theoretical models, assessing such solvent effects over nanoparticles is challenging from a computational standpoint due to the complexity of those liquid/metal interfaces. We investigate this effect by ab initio moleculardynamics simulations at 350 K of a large platinum nanoparticle immersed in liquid water. The first solvation layer contains twice as much physisorbed water molecules above the terraces, than chemisorbed ones located only at edges and corners. The solvent stabilizes the binding energy of chemisorbates: 66 % of the total gain comes from interactions with physisorbed molecules and 34 % from the influence of bulk liquid.

En el area del petroleo una de las principales tareas consiste en separar el agua y gas del crudo, en el presente trabajo se hace un analisis del proceso de separacion en un eparador de prueba trifasico de petroleo instalado en el oriente ecuatoriano para determinar la eficiencia de separacion que se obtiene bajo las mismas condiciones de operacion cuando se utiliza instrumentacion de diferente tecnologia. Para obtener datos en la investigacion de campo se plantea hacer pruebas en el vessel con fluidos de cinco pozos de diferente caudal y con grado API que oscilan entre 18° y 30°, para lo cual se hacen dos tipos de pruebas en el separador, la una con un medidor de interfase de boya instalado entro del recipiente y la otra prueba bajos las mismas condiciones de operacion se utiliza un instrumento de onda guiada. Para determinar la eficiencia de cada metodo utilizado se analiza la cantidad de particulas de agua en crudo en la linea de descarga con pruebas en laboratorio, es asi que se...

Gold nanoparticle (Au NP) mirrors, that exhibit both high reflectance and electrical conductance, were self-assembled at a [heptane + 1,2-dichloroethane]/water liquid/liquid interface. The highest reflectance, as observed experimentally and confirmed by finite difference time domain (FDTD) calculations, occurred for Au NP films consisting of 60 nm diameter NPs and approximate monolayer surface coverage. Scanning electrochemical microscopy (SECM) approach curves over the interfacial metallic NP films revealed a transition from an insulating to a conducting electrical material on reaching a surface coverage at least equivalent to the formation of a single monolayer. Reflectance and conductance transitions were interpreted as critical junctures corresponding to a surface coverage that exceeded the percolation threshold of the Au NP films at the [heptane + 1,2-dichloroethane]/water interface. http://pubs.acs.org.

Gold nanoparticle (Au NP) mirrors, that exhibit both high reflectance and electrical conductance, were self-assembled at a [heptane + 1,2-dichloroethane]/water liquid/liquid interface. The highest reflectance, as observed experimentally and confirmed by finite difference time domain (FDTD) calculations, occurred for Au NP films consisting of 60 nm diameter NPs and approximate monolayer surface coverage. Scanning electrochemical microscopy (SECM) approach curves over the interfacial metallic NP films revealed a transition from an insulating to a conducting electrical material on reaching a surface coverage at least equivalent to the formation of a single monolayer. Reflectance and conductance transitions were interpreted as critical junctures corresponding to a surface coverage that exceeded the percolation threshold of the Au NP films at the [heptane + 1,2-dichloroethane]/water interface. http://pubs.acs.org.

Smart materials with unique surface wetting properties have attracted considerable interest, particularly for oil/water separation, where oil can cause severe environmental damage. Despite 2 the considerable progress made in the past decade, critical challenges remain in scaling up, as smart materials are either expensive to fabricate or involve complicated, energy-intensive, and/or time-consuming production processes. In this work, an ultra-facile approach to fabricate hierarchical Zeolitic Imidazolate Framework-L (ZIF-L) mesh films with switchable superwettability for efficient oil/water separation was reported for the first time. A thick, continuous layer of well-intergrown ZIF-L nanoplates with an average aspect ratio of ~25 was successfully synthesized on various stainless steel (SS) meshes at ambient conditions. The ZIF-L mesh films exhibited extraordinary in-air superamphiphilic, underwater superoleophobic and underoil superhydrophobic properties, and showed outstanding performance in solely-gravitydriven oil/water mixture separation. Interestingly, a prewetting-induced switchable permeation function was found for the hierarchical ZIF-L surface, truly achieving "oil-blocking" and "water-blocking" separation. The ZIF-L mesh films demonstrated superior cyclic separation performance for a variety of oil/water mixtures with separation efficiencies above 99.99% and satisfactory chemical and mechanical stabilities even in harsh conditions. Their rapid and energy-efficient fabrication is therefore highly promising for cost-efficient and large-scale production for widespread applications in oil/water separation.

Commissioning results of a liquid sample cell for X-ray reflectivity studies with an in situ applied electrical field are presented. The cell consists of a Plexiglas container with lateral Kapton windows for air-liquid and liquid-liquid interface studies, and was constructed with grooves to accept plate electrodes on the walls parallel to the direction of the beam. Both copper and ITO plate electrodes have been used, the latter being useful for simultaneous optical studies. Commissioning tests were made at the I07 beamline of the Diamond Light Source.

Public concern towards solidification of fat, oil, and grease (FOG) through disposed wastes into the drainage system is an unresolved issue to this day. The use of skimmer to separate oil and water form their mixture is a less comprehensive solution. This paper aimed to design the concept and fabricate oil-water separation medium, as well as to analyse the effect of different pore sizes of wire mesh and coating respectively. Water separation system is designed based on Pugh Method, while stainless steel wire mesh is used in analysing the water repellent and oil absorption characteristics. Titanium dioxide is used as coating. Surface characterization and contact angle of droplet were observed using scanning electron microscope and contact angle measurement tools. Hydrophobicity of uncoated stainless steel of wire mesh will increase if the pore size of wire mesh is decreasing in size. The more layers of coating increase the hydrophobicity of the wire mesh in increments with contact an...

Ultrafast laser structuring has proven to alter the wettability performance of surfaces drastically due to controlled modification of the surface roughness and energy. Surface alteration can be achieved also by coating the surfaces with functional materials with enhanced durability. On this line, robust and tunable surface wettability performance can be achieved by the synergic effects of ultrafast laser structuring and coating. In this work, femtosecond laser-structured stainless steel (SS-100) meshes were used to host the growth of NaAlSi2O6–H2O zeolite films. Contact angle measurements were carried on pristine SS-100 meshes, zeolite-coated SS-100 meshes, laser-structured SS-100 meshes, and zeolite-coated laser-structured SS-100 meshes. Enhanced hydrophilic behavior was observed in the zeolite-coated SS-100 meshes (contact angle 72°) and in laser-structured SS-100 meshes (contact angle 41°). On the other hand, superior durable hydrophilic behavior was observed for the zeolite-coat...

Due to the increased industrial oily wastewater, developing a successful oil/water separation mechanism is a ubiquitous challenge. As oil/water separation is an interfacial phenomenon, a straightforward way is to utilize the special wettability of novel materials towards oil and water. In this work, we intend to construct a durable membrane/mesh that can have a selective response towards oil and water based on the difference in surface tension. Graphene oxide (GO) is one such material that exhibits in-air hydrophilicity and underwater superoleophobicity. GO-coated wire meshes can act as membranes with excellent efficiency for oil/water separation, but they lack longterm durability for repeated use under different environments. We created GO*-coated wire meshes by dip coating multiple layers of GO with intermediate air plasma treatment. While the multiple steps of coating ensured complete coverage of the mesh with GO, plasma treatment improved the binding of the GO coating to the wire mesh. After coating five GO layers, the mesh is subjected to mild plasma treatment to improve the porosity. The GO*-coated mesh is extremely hydrophilic in air, and the underwater oil contact angles (CA) are $125°f or different oils. To test the long-term durability, the GO*-coated mesh is continuously immersed underwater in acidic and basic media, and the underwater oil CA is measured at different immersion times. The initial durability results are very promising and show that the GO*coated mesh retains a significant level of underwater oleophobicity even after 60 days of continuous immersion in water.

h i g h l i g h t s A reservoir fluid geodynamics model was developed to model asphaltene gradients in oil columns during gas charges. Asphaltene instability was also analyzed by the thermodynamic model with the same parameters in the RGF model. Asphaltene is unstable at the base of the oil column due to a late gas charge in Well 2. A tar mat was formed when asphaltene flocculation occurs at the base of the oil column over geological time.

h i g h l i g h t s A reservoir fluid geodynamics model was developed to model asphaltene gradients in oil columns during gas charges. Asphaltene instability was also analyzed by the thermodynamic model with the same parameters in the RGF model. Asphaltene is unstable at the base of the oil column due to a late gas charge in Well 2. A tar mat was formed when asphaltene flocculation occurs at the base of the oil column over geological time.

The structure of asphaltenes of various maturities prepared by semiopen pyrolysis of Green River Shale is measured by elemental analysis, laser desorption laser ionization mass spectrometry (L 2 MS), surface assisted laser desorption ionization (SALDI) mass spectrometry, sulfur X-ray absorption near edge structure (XANES) spectroscopy, and infrared (IR) spectroscopy. These measurements demonstrate systematic changes in the composition of asphaltenes during thermal maturation. At low maturities, the evolution of asphaltene composition is dominated by changes in the heteroatoms: total sulfur as well as carbon−oxygen, sulfur−oxygen (sulfoxide), and aliphatic carbon−sulfur (sulfide) bonds are lost, while the molecular weight increases. At high maturities, the sulfur content and speciation as well as molecular weight are relatively constant while the evolution in composition is dominated by changes in the carbon backbone: the abundance of aromatic relative to aliphatic carbon increases, the length of aliphatic chains shortens, and the abundance of aromatic C−H bonds increases greatly. The distribution of different carbon−oxygen functional groups is relatively unchanged over the entire maturity range. These changes sometimes mirror and sometimes oppose compositional changes in the bitumen, suggesting that the composition of the asphaltene and maltene fractions of bitumen evolve differently. The observed changes in asphaltene structure are not fully independent of one another, as the composition of asphaltenes is constrained to maintain a balance of the strength of intermolecular forces to ensure solubility in aromatic solvent and insolubility in aliphatic solvent (the definition of asphaltenes). That constraint leads to a decrease in sulfoxide content (weakening intermolecular forces by reducing dipole interactions) concurrent with an increase in molecular weight (strengthening intermolecular forces). These trends in asphaltene composition with maturity are expected to occur in naturally occurring source rocks, such as some tight-oil formations, but not necessarily in conventional reservoir rocks where the asphaltenes escape from the source rock and enter the reservoir during maturation.

For the effective oil/water separation, a novel superhydrophilic (underwater superoleophobic) filter is fabricated with the naturally and hydrothermally treated mica particles. To fabricate a double layerd filter, hydrothermally treated mica particles were initially electrodeposited on a stainless steel mesh and a natural mica particles were sprayed on the first hydrothermally deposited mica layer. The double layerd mica coated membrane showed superamphiphilic and superhydrophilic/superoleophobic (contact angle >159 •) characteristics in air and underwater respectively. The membrane can separate range of oil-water mixtures with oil/water separation efficiency over ~99%. Properties of double layered mica membran were investigated and noted that the surface adhesion properties of mica is enhanced by the hydrothermal treatment of mica and the higher roughness of the mica layer is maintained by the natural mica.

In this report, we investigated the TiO 2 nanofibers coated stainless steel mesh as a novel underwater superoleophobic membrane for the effective separation of contaminated oil-water mixtures. The membrane was fabricated by spray deposition of hydrothermally synthesized TiO 2 nanofibers on stainless steel mesh. The fabricated membrane exhibits superhydrophilicity and supereleophobicity properties in air and underwater respectively allowing the separation of oilwater efficiently. Randomly deposited TiO 2 nanofibers on mesh exhibit rough surface property and hence superhydrophilic nature. Water oil separation efficiencies of ~90 and ~99% were achieved with this filter for less viscous and highly viscous oil respectively. Additionally, the TiO 2 nanofibers coated mesh can degrade immiscible organic molecules due to photocatalytic activity of TiO 2 nanofibers under UV light. As a result of self-cleaning property of TiO 2 nanofibers coated mesh, the durability of the filter membrane was enhanced.

The structure of asphaltenes of various maturities prepared by semiopen pyrolysis of Green River Shale is measured by elemental analysis, laser desorption laser ionization mass spectrometry (L 2 MS), surface assisted laser desorption ionization (SALDI) mass spectrometry, sulfur X-ray absorption near edge structure (XANES) spectroscopy, and infrared (IR) spectroscopy. These measurements demonstrate systematic changes in the composition of asphaltenes during thermal maturation. At low maturities, the evolution of asphaltene composition is dominated by changes in the heteroatoms: total sulfur as well as carbon−oxygen, sulfur−oxygen (sulfoxide), and aliphatic carbon−sulfur (sulfide) bonds are lost, while the molecular weight increases. At high maturities, the sulfur content and speciation as well as molecular weight are relatively constant while the evolution in composition is dominated by changes in the carbon backbone: the abundance of aromatic relative to aliphatic carbon increases, the length of aliphatic chains shortens, and the abundance of aromatic C−H bonds increases greatly. The distribution of different carbon−oxygen functional groups is relatively unchanged over the entire maturity range. These changes sometimes mirror and sometimes oppose compositional changes in the bitumen, suggesting that the composition of the asphaltene and maltene fractions of bitumen evolve differently. The observed changes in asphaltene structure are not fully independent of one another, as the composition of asphaltenes is constrained to maintain a balance of the strength of intermolecular forces to ensure solubility in aromatic solvent and insolubility in aliphatic solvent (the definition of asphaltenes). That constraint leads to a decrease in sulfoxide content (weakening intermolecular forces by reducing dipole interactions) concurrent with an increase in molecular weight (strengthening intermolecular forces). These trends in asphaltene composition with maturity are expected to occur in naturally occurring source rocks, such as some tight-oil formations, but not necessarily in conventional reservoir rocks where the asphaltenes escape from the source rock and enter the reservoir during maturation.

Many physical problems require explicit knowledge of the equilibrium shape of the interface between two fluid phases. Here, we present a new numerical method which is simply implementable and easily adaptable for a wide range of problems involving capillary deformations of fluid-fluid interfaces. We apply a simulated annealing algorithm to find the interface shape that minimizes the thermodynamic potential of the system. First, for completeness, we provide an analytical proof that minimizing this potential is equivalent to solving the Young-Laplace equation and the Young law. Then, we illustrate our numerical method showing two-dimensional results for fluid-fluid menisci between vertical or inclined walls and curved surfaces, capillary interactions between vertical walls, equilibrium shapes of sessile heavy droplets on a flat horizontal solid surface, and of droplets pending from flat or curved solid surfaces. Finally, we show illustrative three-dimensional results to point out the applicability of the method to micro-or nano-particles adsorbed at a fluid-fluid interface.

Three-dimensional (3D)-printed membranes via stereolithography (SLA) are promising in oil−water separation, which is the key in the purification of industrial oily wastewater. To achieve gravity-driven oil−water separation, the membrane material needs to be simultaneously hydrophilic/oleophobic. However, most of the state-of-the-art materials for SLA do not meet the requirement. While wateradsorbing hydrogel is simultaneously hydrophilic/oleophobic and there have been reports on 3D printing of hydrogels in biomedical applications, the hydrogel is too soft for membrane application. Here, we report a simple approach to tackle the issue: a hydrogel coating on SLA-based plastic membranes. The coating is fabricated, using [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide as the zwitterionic monomer and acrylamide as the comonomer, via in situ polymerization on SLA-based plastic membranes. The contact angle tests and Fourier transform infrared spectrum show that such a membrane readily adsorbs water and becomes simultaneously hydrophilic/oleophobic. The oil−water separation tests indicate that the water-adsorbed membrane is highly efficient in gravitydriven oil−water separation in 31 repeating cycles. Our results indicate the great potential of 3D-printed membranes in oil−water separation.

Oil/water separation becomes a research hotspot because of the frequent oil spill accidents. Although lots of separating membranes with super-wettability have been fabricated to separate oil or water from the mixtures, to separate both heavy (ρ oil > ρ water) and light (ρ oil < ρ water) oil/water mixtures with high efficiency and high flux is still a challenge, especially to obtain a membrane with mechanically robust nanostructures, and simultaneously anti-corrosive and self-cleaning ability. Herein, a novel titania nanostructured mesh membrane with superamphiphilicity in air, and dual superlyophobicity in liquid mediums were fabricated. Both high separation efficiency and flux of more than 99.2% and 16,954 L m −2 h −1 were obtained for both light and heavy oil/water mixtures. Importantly, the TiO 2 mesh membrane showed mechanically robust nanostructures and anti-corrosive ability, which can remain dual superlyophobicity, i.e., both underwater superoleophobicity and underoil superhydrophobicity and high oil-water separating behavior even after immersion in solutions of strong acid, basic, high salty, various organic solvents, and even after being abrased and adhered by pure sands and adhesive tape, respectively. Meanwhile, TiO 2 mesh membrane had shown photocatalytic decomposition of oil and organic molecules under UV irradiation, demonstrating unique self-cleaning and anti-fouling ability of the membranes. Given so many merits of these unique membranes, it is believed to these membranes have great potentials to be used in wastewater treatment and oil spill recovery. ''oil-removing" membranes, which allow oil to penetrate through the membranes [21-35], such as nanostructured layer steel mesh [36], superhydrophobic silica aerogels [37], polytetrafluoroethylene (PTFE) coated metal mesh [38], polydimethylsiloxane (PDMS) coated nanowire membrane [39], fly ash coated superhydrophobic textile [40] and zeolite-coated mesh [41]. Noticeably, all these materials can separate either light (ρ oil < ρ water) or heavy (ρ oil > ρ water) oil from the oil/ water mixtures because of the barrier layer caused by the density difference between oil and water. Briefly, for these "water-removing" type materials, they are unsuitable for separating heavy oil/water mixture (ρ oil > ρ water), because oil will accumulate on the material surface,

Oil-water separation using super-wetting and the selective permeability of membranes for oil or water has great ecological and economic significance. We report on the transition of wettability response, from superhydrophilic underwater-superoleophobic to superhydrophobic-superoleophilic state, by nanostructuring stainless steel and copper meshes using ultrashort femtosecond laser pulses. Our approach is environment-friendly, chemical free, and efficient as it exploits the benefit of aging the processed samples in a high vacuum environment. We optimized the laser scanning parameters, mesh pore size, and aging conditions to produce membranes exhibiting an extraordinary separation efficiency of 98% for the oil-water mixture. A variation in the water and oil contact angles for different meshes is presented as a function of the laser scanning speed. Stainless steel meshes with 150 µm pore size and copper meshes with 100 µm pore size have demonstrated an excellent wettability response for oil and water phases. Vacuum aging causes rapid chemisorption of hydrocarbons on laser-structured surfaces in the absence of water molecules, rapidly transforming the wetting state from superhydrophilic to superhydrophobic.

We describe a novel, low-cost and low-tech method for the fabrication of elastomeric Janus particles with diameters ranging from micrometers to millimeters. This consists of UV-irradiating soft urethane/urea elastomer spheres, which are then extracted in toluene and dried. The spheres are thus composed of a single material: no coating or film deposition steps are required. Furthermore, the whole procedure is carried out at ambient temperature and pressure. Long, labyrinthine corrugations ("wrinkles") appear on the irradiated portions of the particles' surfaces, the spatial periodicity of which can be controlled by varying the sizes of particles. The asymmetric morphology of the resulting Janus particles has been confirmed by scanning electron microscopy, atomic force microscopy, and optical microscopy. We have also established that the spheres behave elastically by performing bouncing tests with dried and swollen spheres. Results can be interpreted by assuming that each sphere consists of a thin, stiff surface layer ("skin") lying atop a thicker, softer substrate ("bulk"). The skin's higher stiffness is hypothesized to result from the more extensive cross-linking of the polymer chains located near the surface by the UV radiation. Textures then arise from competition between the effects of bending the skin and compressing the bulk, as the solvent evaporates and the sphere shrinks.

Emulsion stabilization by native cellulose has been mainly hampered because of its insolubility in water. Chemical modification is normally needed to obtain water-soluble cellulose derivatives. These modified celluloses have been widely used for a range of applications by the food, cosmetic, pharmaceutic, paint and construction industries. In most cases, the modified celluloses are used as rheology modifiers (thickeners) or as emulsifying agents. In the last decade, the structural features of cellulose have been revisited, with particular focus on its structural anisotropy (amphiphilicity) and the molecular interactions leading to its resistance to dissolution. The amphiphilic behavior of native cellulose is evidenced by its capacity to adsorb at the interface between oil and aqueous solvent solutions, thus being capable of stabilizing emulsions. In this overview, the fundamentals of emulsion formation and stabilization by biomolecules are briefly revisited before different aspects ...

We describe a novel, low-cost and low-tech method for the fabrication of elastomeric Janus particles with diameters ranging from micrometers to millimeters. This consists of UV-irradiating soft urethane/urea elastomer spheres, which are then extracted in toluene and dried. The spheres are thus composed of a single material: no coating or film deposition steps are required. Furthermore, the whole procedure is carried out at ambient temperature and pressure. Long, labyrinthine corrugations ("wrinkles") appear on the irradiated portions of the particles' surfaces, the spatial periodicity of which can be controlled by varying the sizes of particles. The asymmetric morphology of the resulting Janus particles has been confirmed by scanning electron microscopy, atomic force microscopy, and optical microscopy. We have also established that the spheres behave elastically by performing bouncing tests with dried and swollen spheres. Results can be interpreted by assuming that each sphere consists of a thin, stiff surface layer ("skin") lying atop a thicker, softer substrate ("bulk"). The skin's higher stiffness is hypothesized to result from the more extensive cross-linking of the polymer chains located near the surface by the UV radiation. Textures then arise from competition between the effects of bending the skin and compressing the bulk, as the solvent evaporates and the sphere shrinks.

A photo-responsive TiO2-coated stainless-steel mesh membrane (TiO2@SSM), possessing unique surface wettability, was fabricated. This TiO2@SSM membrane is found to be capable of separating oil and water from oily water and has the potential to carry out photocatalytic self-cleaning and/or the degradation of organic pollutants present in water. The fabrication of TiO2@SSM is quite simple: titanium dioxide (TiO2) nanoparticles were spray-coated onto stainless steel microporous mesh (SSM) substrates and annealed at the temperature of 500 °C. The fabricated TiO2@SSM membrane was structurally and morphologically characterized by XRD, FE-SEM, EDX, and elemental mapping. The contact angle measurements using a goniometer showed that the fabricated TiO2@SSM membrane surface is superhydrophilic and superoleophilic in air and superoleophobic under water. This is a favorable wetting condition for the water passing oil–water separation membrane, and this water passing property of the membrane eas...

Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology have been combined to yield powerful new insights to reservoir tar mats. The asphaltene nanoscience model, the modified Yen model, also known as the Yen−Mullins model, has enabled development of the industry's first predictive equation of state for asphaltene concentration gradients. This equation of state (EOS) is a modified Flory−Huggins regular solution model for the asphaltene part that has been referred to as the Flory−Huggins−Zuo (FHZ) EOS for asphaltene concentration gradients in oil reservoirs. Measurement of these gradients using "downhole fluid analysis" coupled with analysis using the FHZ EOS has successfully addressed a variety of reservoir concerns including reservoir connectivity, viscosity gradients, and fluid disequilibrium. The EOS model shows that asphaltene concentration gradients can be large owing to both the gravity term and gas/oil ratio (GOR) gradients. The FHZ EOS is reduced to a very simple formthe gravity term only for low GOR black oils and heavy oilsand heavy oils are shown to exhibit enormous asphaltene concentration gradients in contrast to predictions from conventional models. In this paper, the FHZ EOS has been applied not only to calculate asphaltene concentration gradients but also to predict asphaltene phase instability in oil reservoirs. Two types of tar mats are discussed: one with a large discontinuous increase in asphaltene concentration versus depth typically at the base of an oil column (corresponding to asphaltene phase transition); the second with a continuous increase in asphaltene content at the base of a heavy oil column due to an exponential increase in viscosity with asphaltene content. Both types of tar mats are consistent with the Yen−Mullins model of asphaltenes within the FHZ EOS analysis discussed herein. The predictions are in good agreement with the laboratory and field observations, and the mechanisms of forming these two kinds of tar mats are also discussed. This methodology establishes a powerful new approach for conducting the analyses of asphaltene concentration grading and tar mat formation in oil reservoirs by integrating the Yen−Mullins model and the FHZ EOS with DFA technology.

Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology have been combined to yield powerful new insights to reservoir tar mats. The asphaltene nanoscience model, the modified Yen model, also known as the Yen−Mullins model, has enabled development of the industry's first predictive equation of state for asphaltene concentration gradients. This equation of state (EOS) is a modified Flory−Huggins regular solution model for the asphaltene part that has been referred to as the Flory−Huggins−Zuo (FHZ) EOS for asphaltene concentration gradients in oil reservoirs. Measurement of these gradients using "downhole fluid analysis" coupled with analysis using the FHZ EOS has successfully addressed a variety of reservoir concerns including reservoir connectivity, viscosity gradients, and fluid disequilibrium. The EOS model shows that asphaltene concentration gradients can be large owing to both the gravity term and gas/oil ratio (GOR) gradients. The FHZ EOS is reduced to a very simple formthe gravity term only for low GOR black oils and heavy oilsand heavy oils are shown to exhibit enormous asphaltene concentration gradients in contrast to predictions from conventional models. In this paper, the FHZ EOS has been applied not only to calculate asphaltene concentration gradients but also to predict asphaltene phase instability in oil reservoirs. Two types of tar mats are discussed: one with a large discontinuous increase in asphaltene concentration versus depth typically at the base of an oil column (corresponding to asphaltene phase transition); the second with a continuous increase in asphaltene content at the base of a heavy oil column due to an exponential increase in viscosity with asphaltene content. Both types of tar mats are consistent with the Yen−Mullins model of asphaltenes within the FHZ EOS analysis discussed herein. The predictions are in good agreement with the laboratory and field observations, and the mechanisms of forming these two kinds of tar mats are also discussed. This methodology establishes a powerful new approach for conducting the analyses of asphaltene concentration grading and tar mat formation in oil reservoirs by integrating the Yen−Mullins model and the FHZ EOS with DFA technology.

Asphaltene precipitation during natural depletion and enhanced oil recovery (EOR) methods is one of the problematic challenges, which can affect the production in oil reservoirs. Asphaltenes as the most surface-active agents in the crude oil can interfacially interact with water molecules. As asphaltenes absorb to oil/water interface, water potentially can be involved and affect asphaltenes surface activity. This paper set out to investigate the surface activity of asphaltenes at the oil/water interface. Extensive sets of IFT tests were conducted with synthetic oil extracted from three different real reservoir crude oil samples in the presence of the distilled water. Results showed that IFT changes are not the dominant function of asphaltenes bulk concentration. However, it was revealed that asphaltenes surface concentration, which is dependent on the thermodynamic stability of asphaltenes within the bulk, controls IFT changes. Further, it was shown that IFT changes versus pressure are non-linear, indicating a non-linear function of asphaltenes surface behavior against pressure. Diluting a crude oil sample with normal heptane (n-C7) at various dilution ratios, indicated that dilution with a precipitant causes asphaltenes to be less surface active. The results of this study indicated that aging reduces asphaltenes surface activity only when the crude oil is diluted which revealed that asphaltene precipitation is a timedependent phenomenon. Finally, it identified that sudden pressure shocks have no significant effect on asphaltenes behavior in crude oil. The results of this study shed new light on the mechanism of the asphaltenes surface behavior at oil/water interface which could be of crucial importance in flow assurance engineering as well as water flooding process.

Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology have been combined to yield powerful new insights to reservoir tar mats. The asphaltene nanoscience model, the modified Yen model, also known as the Yen−Mullins model, has enabled development of the industry's first predictive equation of state for asphaltene concentration gradients. This equation of state (EOS) is a modified Flory−Huggins regular solution model for the asphaltene part that has been referred to as the Flory−Huggins−Zuo (FHZ) EOS for asphaltene concentration gradients in oil reservoirs. Measurement of these gradients using "downhole fluid analysis" coupled with analysis using the FHZ EOS has successfully addressed a variety of reservoir concerns including reservoir connectivity, viscosity gradients, and fluid disequilibrium. The EOS model shows that asphaltene concentration gradients can be large owing to both the gravity term and gas/oil ratio (GOR) gradients. The FHZ EOS is reduced to a very simple formthe gravity term only for low GOR black oils and heavy oilsand heavy oils are shown to exhibit enormous asphaltene concentration gradients in contrast to predictions from conventional models. In this paper, the FHZ EOS has been applied not only to calculate asphaltene concentration gradients but also to predict asphaltene phase instability in oil reservoirs. Two types of tar mats are discussed: one with a large discontinuous increase in asphaltene concentration versus depth typically at the base of an oil column (corresponding to asphaltene phase transition); the second with a continuous increase in asphaltene content at the base of a heavy oil column due to an exponential increase in viscosity with asphaltene content. Both types of tar mats are consistent with the Yen−Mullins model of asphaltenes within the FHZ EOS analysis discussed herein. The predictions are in good agreement with the laboratory and field observations, and the mechanisms of forming these two kinds of tar mats are also discussed. This methodology establishes a powerful new approach for conducting the analyses of asphaltene concentration grading and tar mat formation in oil reservoirs by integrating the Yen−Mullins model and the FHZ EOS with DFA technology.

Understanding asphaltene gradients and dynamics of fluids in reservoirs had been greatly hindered by the lack of knowledge of asphaltene nanoscience. Gravitational segregation effects on oil composition, so important in reservoir fluids, are unresolvable without knowledge of (asphaltene) particle size in crude oils. Recently, the &quot;modified Yen model&quot; also known as the Yen-Mullins model, has been proposed describing the dominant forms of asphaltenes in crude oils: molecules, nanoaggregates and clusters. This asphaltene nanoscience approach enables development of the first predictive equation of state for asphaltene compositional gradients in reservoirs, the Flory-Huggins-Zuo (FHZ) EoS. This new asphaltene EoS is readily exploited with &quot;downhole fluid analysis&quot; (DFA) on wireline formation testers thereby elucidating important fluid and reservoir complexities. Field studies confirm the applicability of this scientific formalism and DFA technology for evaluating rese...

Spatial gradients in the chemical composition of crude oil are now routinely observed; oils near the top of a reservoir can be enriched in lighter ends, whereas oils near the bottom of a reservoir are typically enriched in asphaltenes. Equations of state capable of modeling these gradients have numerous practical applications, such as predicting variations in fluid properties, the presence of tar mats, and flow connectivity. Because of the great chemical complexity of crude oil, successful modeling of these gradients requires both an understanding of the physical drivers of the gradients and a set of reasonable simplifying assumptions for describing the composition of the crude oil. Gravity is often a dominant force driving fluid gradients, resulting in separation of low-density gas above medium-density oil above high-density water when those isolated phases are present and frequently driving gradients within a phase as well. The impact of gravity in driving gradients depends in part upon the mass and volume of molecules or aggregates in the crude oil. Here, we explore the impact of gravity in segregating asphaltenes of different masses. Asphaltenes were extracted from crude oils from a connected reservoir with a large gradient in asphaltene content and studied with two mass spectrometric techniques: laser desorption laser ionization mass spectrometry (L 2 MS), which measures the mass of asphaltene molecules, and surface-assisted laser desorption/ionization (SALDI) mass spectrometry, which measures the mass of asphaltene nanoaggregates. No significant gradients in the molecule or nanoaggregate mass were observed, suggesting that gravity causes almost no segregation of different molecular or nanoaggregate masses within the asphaltene class. That is, the large concentration gradient of asphaltenes in the reservoir is not accompanied by a large molecular weight gradient within the asphaltene class. These results indicate that asphaltene gradients can be modeled with the simplifying assumption that gravity drives gradients in the concentration of asphaltenes but not the chemical composition of asphaltenes in crude oil.

Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology have been combined to yield powerful new insights to reservoir tar mats. The asphaltene nanoscience model, the modified Yen model, also known as the Yen−Mullins model, has enabled development of the industry's first predictive equation of state for asphaltene concentration gradients. This equation of state (EOS) is a modified Flory−Huggins regular solution model for the asphaltene part that has been referred to as the Flory−Huggins−Zuo (FHZ) EOS for asphaltene concentration gradients in oil reservoirs. Measurement of these gradients using "downhole fluid analysis" coupled with analysis using the FHZ EOS has successfully addressed a variety of reservoir concerns including reservoir connectivity, viscosity gradients, and fluid disequilibrium. The EOS model shows that asphaltene concentration gradients can be large owing to both the gravity term and gas/oil ratio (GOR) gradients. The FHZ EOS is reduced to a very simple formthe gravity term only for low GOR black oils and heavy oilsand heavy oils are shown to exhibit enormous asphaltene concentration gradients in contrast to predictions from conventional models. In this paper, the FHZ EOS has been applied not only to calculate asphaltene concentration gradients but also to predict asphaltene phase instability in oil reservoirs. Two types of tar mats are discussed: one with a large discontinuous increase in asphaltene concentration versus depth typically at the base of an oil column (corresponding to asphaltene phase transition); the second with a continuous increase in asphaltene content at the base of a heavy oil column due to an exponential increase in viscosity with asphaltene content. Both types of tar mats are consistent with the Yen−Mullins model of asphaltenes within the FHZ EOS analysis discussed herein. The predictions are in good agreement with the laboratory and field observations, and the mechanisms of forming these two kinds of tar mats are also discussed. This methodology establishes a powerful new approach for conducting the analyses of asphaltene concentration grading and tar mat formation in oil reservoirs by integrating the Yen−Mullins model and the FHZ EOS with DFA technology.

Previously, asphaltene science had been hindered by many significant uncertainties regarding molecular weight, molecular structure, and nanocolloidal characteristics in laboratory solvents and in crude oils. These debates were of sufficient magnitude to forestall development and utility of asphaltene modeling for various applications. In the last two decades, advances in asphaltene science using many sophisticated techniques have greatly reduced corresponding uncertainties enabling development of simple asphaltene models for a variety of applications. Here, we provide an overview of key findings in asphaltene science; dominant molecular and nanocolloidal structures are described. These structures with simple thermodynamic formalisms are shown to work well in oilfield reservoirs specifically including light oils, black oils, and heavy oils. This novel thermodynamic approach using asphaltene nanostructures has enabled characterization of different processes that impact or preclude equilibration of reservoir fluids in geologic time. These processes combine to form the new technical discipline, 'reservoir fluid geodynamics,' that has proven value for in many reservoir studies. In addition, these asphaltene nanostructures are shown to apply to interfacial tension of asphaltene solutions, using simple thermodynamics for surfaces

Some aspects of the interfacial behavior of cellulose dissolved in an aqueous solvent were investigated. Cellulose was found to significantly decrease the interfacial tension (IFT) between paraffin oil and 85 wt% phosphoric acid aqueous solutions. This decrease was similar in magnitude to that displayed by non-ionic cellulose derivatives. Cellulose's interfacial activity indicated a significant amphiphilic character and that the interfacial activity of cellulose derivatives is not only related to the derivatization but inherent in the cellulose backbone. This finding suggests that cellulose would have the ability of stabilizing dispersions, like oil-in-water emulsions in a similar way as a large number of cellulose derivatives. In its molecularly dissolved state, cellulose proved to be able to stabilize emulsions of paraffin in the polar solvent on a short-term. However, long-term stability against drop-coalescence was possible to achieve by a slight change in the amphiphilicity of cellulose, effected by a slight increase in pH. These emulsions exhibited excellent stability against coalescence/oiling-off over a period of one year. Ageing of the cellulose solution before emulsification (resulting in molecular weight reduction) was found to favour the creation of smaller droplets.

The thin film balance (TFB) technique was used to measure the equilibrium thicknesses of the water films formed between two oil phases. The measurements were conducted with dodecane at varying concentrations of dodecylammonium chloride, pH and electrolyte. The data obtained in the present work were used to calculate the surface forces acting between the two oil phases. The calculation was carried using the Extended-DL va theory with the surface potentials calculated from the Gibbs adsorption isotherm. The results show that oil droplets suspended in water are hydrophobic and the hydrophobicity changes with surfactant and electrolyte concentrations.

Superhydrophilic and underwater superoleophobic surfaces were fabricated by facile spray coating of nanostructured WO3 on stainless steel meshes and compared its performance in oil-water separation with ZnO coated meshes. The gravity driven oil-water separation system was designed using these surfaces as the separation media and it was noticed that WO3 coated stainless steel mesh showed high separation efficiency (99%), with pore size as high as 150 µm, whereas ZnO coated surfaces failed in the process of oil-water separation when the pore exceeded 50 µm size. Since, nanostructured WO3 is a well known catalyst, the simultaneous photocatalytic degradation of organic pollutants present in the separated water from the oil water separation process were tested using WO3 coated surfaces under UV radiation and the efficiency of this degradation was found to be quite significant. These results assure that with little improvisation on the oil water separation system, these surfaces can be ma...

Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology have been combined to yield powerful new insights to reservoir tar mats. The asphaltene nanoscience model, the modified Yen model, also known as the Yen−Mullins model, has enabled development of the industry's first predictive equation of state for asphaltene concentration gradients. This equation of state (EOS) is a modified Flory−Huggins regular solution model for the asphaltene part that has been referred to as the Flory−Huggins−Zuo (FHZ) EOS for asphaltene concentration gradients in oil reservoirs. Measurement of these gradients using "downhole fluid analysis" coupled with analysis using the FHZ EOS has successfully addressed a variety of reservoir concerns including reservoir connectivity, viscosity gradients, and fluid disequilibrium. The EOS model shows that asphaltene concentration gradients can be large owing to both the gravity term and gas/oil ratio (GOR) gradients. The FHZ EOS is reduced to a very simple formthe gravity term only for low GOR black oils and heavy oilsand heavy oils are shown to exhibit enormous asphaltene concentration gradients in contrast to predictions from conventional models. In this paper, the FHZ EOS has been applied not only to calculate asphaltene concentration gradients but also to predict asphaltene phase instability in oil reservoirs. Two types of tar mats are discussed: one with a large discontinuous increase in asphaltene concentration versus depth typically at the base of an oil column (corresponding to asphaltene phase transition); the second with a continuous increase in asphaltene content at the base of a heavy oil column due to an exponential increase in viscosity with asphaltene content. Both types of tar mats are consistent with the Yen−Mullins model of asphaltenes within the FHZ EOS analysis discussed herein. The predictions are in good agreement with the laboratory and field observations, and the mechanisms of forming these two kinds of tar mats are also discussed. This methodology establishes a powerful new approach for conducting the analyses of asphaltene concentration grading and tar mat formation in oil reservoirs by integrating the Yen−Mullins model and the FHZ EOS with DFA technology.

The ionic state of an adsorbed gemini surfactant at the air/water interface was investigated using a combination of surface potential and surface tension data. The combined model was developed and successfully described the experimental data. The results verified the existence of three ionic states of the gemini surfactant in the interfacial zone. Furthermore, the model can quantify the adsorbed concentrations of these species. At low concentrations, the fully dissociated state dominates the adsorption. At high concentrations, the fully associated state dominates, accounting for up to 80% of the total adsorption. In the middle range, the adsorption is dominated by the partially associated state, which has a maximum percentage of 80% at a critical micelle concentration of 0.5. The variation in the ionic state is a unique characteristic of gemini surfactants, which can be the underlying mechanism for their advantages over conventional surfactants.

A new method was presented to impart polymer substrate with superoleophobic properties. Aluminum/ polymer composite was created by a hot-pressing process, and rough surface textures needed to establish superoleophobicity were created by HCl etching and boiling water treatment. After surface fluorination, the surface became super-repellent towards water and several organic liquids, such as hexadecane. The effect of geometrical structure on hydrophobicity and oleophobicity was investigated, and the result showed that the synergistic action of microterraces and nanoflakes played a key role in establishing oleophobicity. A waterfall/jet test demonstrated that the obtained surface can keep its superoleophobicity after a long time exposure to water. Moreover, the obtained surface did not lose the superoleophobicity after placing it under cold condition for 7 days.

Reservoir crude oils consist of dissolved gases, liquids, and dissolved solids, the asphaltenes. For 40 years, gas-liquid equilibria of crude oils have been treated with cubic equations of state, variants of the van der Waals EoS. However, asphaltenes had eluded a similar thermodynamic treatment. Recently, the molecular and nanocolloidal structures of asphaltenes in crude oil have been developed and codified in the Yen-Mullins model. With sizes known, the gravity term clarifies and can be added to the Flory-Huggins polymer solution theory, yielding the Flory-Huggins-Zuo (FHZ) EoS. Measurement of gradients of crude oils vertically and laterally in reservoirs is best accomplished with "downhole fluid analysis" (DFA). Interpretation of asphaltene gradients with the FHZ EoS allows determination of the extent of thermodynamic equilibrium of reservoir crude oils. Equilibrated crude oils imply flow connectivity in reservoirs, addressing one of the most important uncertainties in reservoirs. Disequilibrium fluid gradients in reservoirs imply ongoing fluid processes in geologic time. Specification of many of these processes in reservoir case studies has led to

Asphaltenes are aromatic hydrocarbons found in crude oils or carbonaceous materials. They are characterized by complex chemistry and their presence in crude oils impacts the oil properties. Phase changes, viscosity, and interfacial properties of crude oils are strongly affected by asphaltenes and, perhaps most importantly, they tend to clump together when exposed to changes in temperature and pressure, such as in pipelines pumping oil up out of underground reservoirs [1]. It is this aggregation of the particles that makes asphaltenes such a problem, once they have come together, they aggregate further and further until they begin to depose onto the walls of the pipe. This poses an obvious issue to oil production, not just in the primary pipelines that first transport the oil (the "upstream" sector) but also in the transportation of that oil and finally the refining of the oil (the "midstream" and "downstream" sectors, respectively) [2]. Therefore, preventing flocculation of asphaltene in crude oil is an important goal.

Femtosecond (FS) laser-induced surface structuring is a robust, maskless, non-contact, and single-step process for producing micro- and nanoscale structures on a material’s surface, which remarkably alters the optical, chemical, wetting, and tribological properties of that material. Wettability control, in particular, is of high significance in various applications, including self-cleaning, anti-fouling, anti-icing, anti-corrosion, and, recently, oil–water separation. Due to growing energy demands and rapid industrialization, oil spill accidents and organic industrial discharges frequently take place. This poses an imminent threat to the environment and has adverse effects on the economy and the ecosystem. Oil–water separation and oil waste management require mechanically robust, durable, low-cost, and highly efficient oil–water manipulation systems. To address this challenge superhydrophobic–superoleophilic and superhydrophilic–underwater superoleophobic membrane filters have shown...

The interfacial properties of poly(maleic acid-alt-1-alkene) disodium salts at hydrocarbon/water interfaces are determined. In all the studied systems, the interfacial tension decreases markedly with the polyelectrolyte concentration as the side-chain length increases. The results of the standard free energy of adsorption, G 0 ads , are a linear function of the number of carbon atoms in the polyelectrolyte side chain. The contribution to G 0 ads per mol of methylene group varies from −0.64 to −0.52 kJ/mol for the n-octane/water to n-dodecane/water interfaces. G 0 ads data also reveal that the adsorption process is mainly determined by adsorption efficiency. Comparatively, the adsorption effectiveness seems to play a less important role. The theoretical interaction energies calculated for the insertion of one hydrocarbon molecule into the space formed by two neighboring polyelectrolyte side chains are in good agreement with the experimental results. The latter results are consistent with van der Waals-type interactions between the hydrocarbon molecules and the polyelectrolyte side chains.

Argentinian crude oil samples from different origins have been processed to separate in the four fractions Saturates, Aromatics, Resins, and Asphaltenes (SARA). Asphaltene and resin fractions were extracted using npentane and n-heptane as precipitating solvents. Sulphur contents of the samples were determined by elemental analysis and X-ray Absorption Spectroscopy at the Sulphur K-edge was used to perform sulphur speciation for resin and asphaltene fractions. Reduce sulphur as sulphides, disulphides and thiophenes dominate the spectra of asphaltenes, resins I and crude oils samples. A higher abundance of sulfoxide forms were found in the resin II fraction. In addition, it was found that the asphaltenes are more enriched in aromatic sulphur (thiophene) when the n-heptane solvent is employed. From the sulphur speciation determination it was possible to incorporate different sulphur forms in the hypothetical average molecular structures for the Argentinian asphaltenes.

Recent advances in the understanding of the molecular and colloidal structure of asphaltenes in crude oils are codified in the Yen−Mullins model of asphaltenes. The Yen−Mullins model has enabled the development of the industry's first asphaltene equation of state for predicting asphaltene concentration gradients in oil reservoirs, the Flory−Huggins−Zuo equation of state (FHZ EOS). The FHZ EOS is built by adding gravitational forces onto the existing Flory−Huggins regular solution model that has been used widely to model the phase behavior of asphaltene precipitation in the oil and gas industry. For reservoir crude oils with a low gas/oil ratio (GOR), the FHZ EOS reduces predominantly to a simple form, the gravity term only, and for mobile heavy oil, the gravity term simply uses asphaltene clusters. The FHZ EOS has successfully been employed to estimate the concentration gradients of asphaltenes and/or heavy ends in different crude oil columns around the world, thus evaluating the reservoir connectivity, which has been confirmed by the subsequent production data. This paper reviews recent advances in applying the FHZ EOS to different crude oil reservoirs from volatile oil (condensate) to black oil to mobile heavy oil all over the world to address key reservoir issues, such as reservoir connectivity/compartmentalization, tar mat formation, non-equilibrium with a late gas charge, and asphaltene destabilization. The workflow incorporates the integration of new technology, downhole fluid analysis (DFA), coupled with the new scientific advances, the FHZ EOS and Yen−Mullins model. The combination proves a powerful new method of reservoir evaluation. Asphaltene or heavy end concentration gradients in crude oils are treated using the FHZ EOS, explicitly incorporating the size of resin molecules, asphaltene molecules, asphaltene nanoaggregates, and/or asphaltene clusters. All of the parameters in the FHZ EOS are related to DFA measurements, such as compositions, GOR, density, etc. The variations of gas and oil properties with depth are calculated by the classical cubic equation of state (EOS) based on DFA compositions and GOR using specifically developed delumping, characterizing, and oil-based drilling mud (OBM) contamination correcting techniques. Field case studies have proven the value and simplicity of this asphaltene or heavy end treatment. Heuristics can be developed from results corresponding to estimation of asphaltene gradients. Perylene-like resins with the size of ∼1 nm are dispersed as molecules in high-GOR volatile oils with high fluorescence intensity and virtually no asphaltenes (0 wt % asphaltene). Heavy asphaltene-like resins with the size of ∼1.3 nm are molecularly dissolved in volatile oil at a very low asphaltene content. Asphaltene nanoaggregates with the size of ∼2 nm are dispersed in stable crude oil at a bit higher asphaltene content. Asphaltene clusters are found in mobile heavy oil with the size of ∼5 nm at even higher asphaltene content (typically >8 wt % based on stock tank oil). Two types of tar mats are identified by the FHZ EOS: one with a large discontinuous increase in asphaltene content versus depth typically at the base of an oil column (corresponding to asphaltene phase transition) and one with a continuous increase in asphaltene content at the base of a heavy oil column simply by extending the oil column in the downdip direction because of an exponential increase in viscosity with asphaltene content. All of these studies are in accordance with the observations in the Yen−Mullins model within the FHZ EOS analysis.