Oil Wettability Research Articles

Utilization of recycled polyester nonwovens as sorbent for oil spill cleanups

Purpose The most widely recycled plastic in the world is recycled polyethylene terephthalate (rPET). To minimize the environmental related issues associated with synthetic fibers, several researchers have explored the potential use of recycled polyester fibers in developing various technical textile products. This study aims to develop needle-punched nonwoven fabrics from recycled polyester fibers and investigate its suitability in oil spill cleanup process. Design/methodology/approach According to Box and Behnken factorial design, 15 different needle-punched nonwoven fabrics from recycled polyester fibers were prepared by changing the parameters, namely, needle punch density, needle penetration depth and fabric areal weight. Several featured parameters such as oil sorption, oil retention, oil sorption kinetics, wettability and reusability performance were systematically elucidated. Findings The maximum oil sorption of recycled nonwoven polyester is found to be 24.85 g/g and 20.58 g/g for crude oil and vegetable oil, respectively. The oil retention is about 93%–96% in case of crude oil, whereas 87%–91% in case of vegetable oil. Recycled polyester nonwoven possesses good hydrophobic–oleophilic properties with static contact angle of 138° against water, whereas 0° against crude oil and vegetable oil. The reusability test results indicate that recycled polyester nonwoven fabric can be used several times because of its reusability features. Originality/value There is no detailed study on the oil sorption features of needle-punched nonwoven fabrics developed from recycled polyester fibers. This study is expected to help in developing fabrics for oil spill cleanups.

The role of MFC and hydrophobically modified ethyl(hydroxyethyl)cellulose in film formation and the barrier properties of methyl nanocellulose film

Abstract There is currently a great demand for sustainable and bio-derived coatings for fiber-based packaging materials, which are technically implementable with a high performance. The aim of this work was to investigate the grease resistance of coatings prepared from methyl nanocellulose when applied on paperboard. Co-additives selected from native microfibrillated cellulose (MFC) and hydrophobically modified ethyl(hydroxyethyl)cellulose (EHEC) were used in order to determine their impact on film formation and crack resistance for folds. Small and moderate coat weights were applied in order to determine the critical coat weight for the barrier properties. It was found that high grease resistance can be achieved with methyl nanocellulose and a combination of methyl nanocellulose and MFC coatings. Contact angle determinations for water on uncoated and coated materials showed that EHEC-MFC films have a very high contact angle which is due to both the surface chemistry and roughness. This indicates and confirms that EHEC may facilitate the wetting of oil and greases. Methyl nanocellulose mixed with hydrophobically modified EHEC significantly changed the barrier properties indicating a change in the film formation.

Quality assessment of flour and cookies from wheat, African yam bean and acha flours

In this study, the suitability of wheat, acha and African yam bean composite flour in the development of cookies was investigated. Wheat, acha and African yam bean were blended into various proportions of flour mixes and used to produce cookies. The flour mixes were analyzed for the proximate, minerals composition, functional properties and anti-nutrients, while the cookies were evaluated for its sensory and physical properties. The proximate composition of the flours varied from 7.85-9.71%, 12.34-14.01%, 1.15- 1.86%, 1.21-1.49%, 1.65-1.92% and 70.01-76.11% for moisture, protein, fat, crude fiber, ash and carbohydrate content of the flour, respectively. The mineral content ranged from 10.11-13.12 mg/100 g, 52.65-61.76 mg/100 g, 130.71-211.76 mg/100 g, 111.97-130.84 mg/100 g and 14.81-20.43 mg/100 g for calcium, magnesium, potassium, phosphorus and sodium, respectively. The functional properties ranged from 0.76-0.80 g/cm3 ; 86.65- 188.11 g/g; 94.30-197.23 g/g; 569.23-699.54%; 5.68-6.44%; 61.50-125.50 sec, 73.75- 75.25% for bulk density, water absorption capacity, oil absorption capacity, swelling capacity, solubility, wettability and dispersiblity respectively. The anti-nutritional properties ranged from 37.67 to 46.73 mg/100 g, 5.27 to 5.57 mg/100 g and 32.91 to 35.10 mg/100 g for oxalate, phytate and tannin, respectively. The physical properties values ranged from 6.11-8.20 mm, 38.46-39.30 mm, 37.83-38.23 mm, 4.79-5.85, 5.35-7.49 g and 1.72-1.90 kg for thickness, diameter, height, spread ratio, weight and break strength respectively. Cookies from composite flours were not significantly (p>0.05) different from the control in overall acceptability. This shows the possibility of producing nutritious cookies with desirable organoleptic qualities from wheat, acha and African yam bean flour.

Numerical investigation of effects on replenishment in rolling point contacts using CFD simulations

A lubricating film prevents a rolling bearing from high friction and wear by separating the contacting surfaces. In grease lubricated contacts the bled oil induces a hydrodynamic film formation. At high rolling speeds, more bled oil is displaced than replenished, which leads to lubricant starvation. To predict the film formation under starvation, the lubricant supply by replenishment must be determined. However, the effects on oil replenishment are not fully clarified. In particular, the effects of oil wettability as well as the available bled oil amount on the replenishment are not sufficiently investigated. Therefore, in this contribution the oil flow around a rolling point contact is examined under limited oil volume and in dependence of oil wettability, using CFD simulations.

Femtosecond laser-induced shape memory polymer micropillar with tunable wettability and reversible adhesion for underwater oil droplet lossless transfer

Shape memory polymers (SMPs) with tunable wettability and reversible adhesion through adjusting the surface morphology have great prospects in functional devices. However, current functional devices based on SMPs are mainly concentrated on the manipulation of diverse liquid droplets in the air; it is still a challenge to achieve the reversible tuning of underwater oil wettability and adhesion on the microstructured SMP surface. Herein, we fabricate a kind of SMP micropillar array through one-step femtosecond laser irradiation, which could achieve the reversible tuning of underwater oil wettability and adhesion between the tilted and upright states. It is worth noting that the deformed micropillar arrays show underwater oleophobicity and have a larger adhesion force to the oil droplet than that of upright micropillar arrays, which is mainly related to the variation of the contact area between the oil droplet and the micropillar array. Finally, we demonstrate the lossless oil droplet transfer underwater by using the micropillar array surface with different states. We believe the present work will bring some insights for researchers in the field of dynamically responsive tunable underwater oil droplet manipulation.

Temperature Effect on Oil Sorption and Wettability of Kapok Fiber

ABSTRACT Kapok fiber as a natural sorbent with excellent hydrophobic-oleophilic characteristic was studied. The effect of temperature on oil sorption behavior and wettability of kapok fiber powder was quantitatively evaluated by capillary rise method. Results showed that at the packing density of 0.1 g/cm3, the oil sorption capacity of kapok fiber powder presented only about 5% difference when the temperature ranged from 20°C to 90°C, with the values to engine oil, mineral oil, and PAO4 ranging from 10.96 to10.42 g/g, 10.73 to 10.18 g/g, and 10.25 to 9.89 g/g, respectively. However, the sorption coefficient which related to the sorption rate increased almost exponentially with the increasing of temperature. Then, the oil wettability of kapok fiber powder was further investigated from the perspective of contact angle. Nearly logarithmic increment in contact angle between the fiber powder and test oil was observed when higher temperature condition was applied, indicating that the enhancement of temperature apparently weaken the wettability of oil to solid powder. The adhesion work between fiber powder and oil was evaluated based on Young–Dupré equation, which suggested that higher temperature lead to lower adhesion work. Outcomes from this research are believed to provide importance reference for the usage of kapok fiber as sorbent when different temperatures are applied.

Investigations on the adsorption, wettability and zeta potential of anionic surfactant in limestone.

The understanding of the mechanisms that affect oil production in carbonaceous reservoirs has become increasingly necessary, particularly in limestone, which mostly features oil wettability properties that diminishes petroleum recovery. The objective of this work was to investigate the ability of anionic surfactant (coconut oil derived soap) to adsorb in limestone in order to promote wettability change. The finite-bath technique was employed with changes in temperature, mass of adsorbent material (limestone), contact time and surfactant concentration. Contact angle and zeta potential measurements were also made. The surfactant could be significantly adsorbed on the rock, possibly due to ions that are charged oppositely to the species on the rock surface. A temperature rise from 30 °C to 50 °C was unfavourable to the adsorption capacity. The oil-wettable in-natura limestone had its wettability reduced after the treatment with surfactant. The zeta potential measurements showed that electrostatic attractions play an important role in the adsorption process.

Modification Wettability and Interfacial Tension of Heavy Crude Oil by Green Bio-surfactant Based on Bacillus licheniformis and Rhodococcus erythropolis Strains under Reservoir Conditions: Microbial Enhanced Oil Recovery

Oil spill contamination in soil is still problematic. At the same time, petroleum-contaminated soil in oil reservoirs contain various microbes, which have the ability for biosurfactant production. Extracting these biosurfactants is a very promising and cost-effective strategy for the microbial enhanced oil recovery process. Biosurfactants production using Bacillus licheniformis AnBa7 and Rhodococcus erythropolis sp., isolated from Egyptian crude oils, was enhanced using various carbon sources. The best biosurfactant characteristics were observed when 1% of crude oil was used as a carbon source. The production was further improved by using a developed fed-batch cultivation strategy depends on using 1% Glucose as a single addition at the beginning of the culture. Then 1% of crude oil was added three times during the production process. This strategy enhanced surfactin and trehalose productivity by 1.8 and 4.7 fold higher than the normal conditions, respectively. The surface-active and thermodynamic properties were studied. The results indicated that the calculated values of ΔGmic for surfactin complex, and trehalose complex were −18.47 and −18.28 kJ/mol at 60 °C, respectively while ΔGads values were −30.42 and −29.46 kJ/mol at 60 °C. The interfacial tension (IFT) values of surfactin complex and trehalose complex systems were ranging from 0.75 to 0.19 mN m–1 and from 0.93 to 0.26 mN m–1 at 60 °C, respectively. However, the (IFT) for the blank solution was ∼11.57 mN m–1, and the wettability was changed to an excellent water-wet state (θ = ∼ 17.42–24.0°). The core-flooding studies showed that the enhanced oil recovery for surfactin complex and trehalos complex, at maximum concentration 6 g/L, were 59.21% and 51.83%, respectively. A predicted mechanism was illustrating through the text.

Reversible Wettability between Underwater Superoleophobicity and Superhydrophobicity of Stainless Steel Mesh for Efficient Oil-Water Separation.

Design and fabrication of smart materials with reversible wettability for oil–water separation have attracted worldwide attention due to the increasingly serious water pollution problem. In this study, a rough oxide coating with micro/nanoscale structures is developed on the 304 stainless steel mesh (SSM) by laser ablation. The smart surface with ethanol immersion and natural drying treatments shows the wetting conversion between underwater superoleophobicity and superhydrophobicity. Based on the wettability transition behavior, both light and heavy oil–water mixtures can be separated with the high separation efficiency. Moreover, after being exposed to various corrosive solutions and high temperatures, the smart surface still shows prominent environmental stability. Switchable surface with excellent properties should be an optimal choice to solve the environmental conditions that need to be addressed urgently.

An introductory investigation of a polymeric surfactant from a new natural source in chemical enhanced oil recovery (CEOR)

Greater than 50% of the original oil in place turns into immobile or trapped oil because of unfavored mobility and capillary forces problems. More efficient methods should be introduced in the tertiary oil recovery section as a scheme of Enhanced Oil Recovery (EOR). Surface-active-agents presented as surfactants play an important role in chemical EOR by their ability to optimize the operative parameters of interfacial/surface tension, wettability state, and modify the mobility of fluids in EOR processes. Beside all these optimizations induced to the fluid and rock of the reservoir, surfactants like other materials experience molecule losses by adsorption of solid/liquid interface. Great loss of surfactant molecules causes expensive materials cost and ineffectiveness of the benefits of these surface-active agents. Also, as literature reported, natural surfactants possess lower production costs, lower adsorption capacity, and environmentally friendly. This study introduces a new natural polymeric surfactant governed from the Acanthephyllum plant. Aqueous extraction process conducted and the extract was characterized by Fourier Transform Infrared spectroscopy (FTIR), Thermo-Gravimetric Analysis (TGA), and Proton Nuclear Magnetic Resonance spectroscopy (H-NMR). Characterization tests confirmed the polymeric state of the extract and the existence of surface-active functional groups in the extract. Interfacial tension (IFT) and surface tension (ST) between water-oil and water-air was measured respectively and showed a 92.6 and 61.6 percent optimization in their initial values in turn. Wettability alteration evaluated on a carbonate rock/crude oil/natural surfactant solution system and changed the oil wetness state of the initial oil-wet carbonate rock to a water wetness state because the wettability alteration measurements showed a reduction of the contact angle from 146° to 64° for only 80 min as the equilibrium time. Adsorption experiments conducted as adsorption isotherms and kinetic models. Freundlich isotherm fitted as the best model, and comparison of kinetic adsorption models for Acanthephyllum plant root extract as polymeric surfactant uptake shows that the pseudo-second-order model has the best accuracy and the pseudo-first-order model has the lowest accuracy.

Experimental study of nanoparticle size and material effect on the oil wettability characteristics of various rock types

The paper presents the results of systematic experimental studies of interfacial tension (IFT) and oil wettability of three different types of rock (dolomite, metabasalt, and sandstone) in nanosuspensions. Nanoparticles of silicon and aluminum oxides were used at the concentration ranged from 0.01 to 1 wt%. It is shown that with increasing NP concentration, the contact angle of an oil droplet resting on a rock in a nanosuspension increases quite essentially (from 33 to 153°). The nanoparticle size and compositional effects on interfacial tension coefficient and contact angle (CA) within a wide range of particle concentrations were systematically studied for the first time. The contact angle oil/dolomite/nanofluid increased from 92 to 151° with decrease in the SiO2 nanoparticle size 50 nm to 5 nm. With an increase in the NP size from 5 to 50 nm, there was a decrease in interfacial tension of about 30%. The first-ever experiments were conducted to study the influence of nanoparticles in water on the oil wettability of various types of hydrophilic and hydrophobic rocks. It is shown that the wettability characteristics of various types of rocks can be controlled by adding minor amounts of nanoparticles of different sizes and compositions to influence the parameters that play a key role in the problems related to oil recovery enhancement during reservoir flooding.

Detection of Corrosion-Indicating Oxidation Product Colors in Steel Bridges under Varying Illuminations, Shadows, and Wetting Conditions

Early detection of corrosion in steel bridges is essential for strategizing the mitigation of further corrosion damage. Although various image-based approaches are available in the literature for corrosion detection, most of these approaches are tested on images acquired under uniform natural daylight illuminations i.e., inherent variations in the ambient lighting conditions are ignored. Owing to the fact that varying natural daylight illuminations, shadows, water wetting, and oil wetting are unavoidable in real-world scenarios, it is important to devise a robust technique for corrosion identification. In the current study, four different color spaces namely ‘RGB’, ‘rgb’, ‘HSV’ and ‘CIE La*b*’ along with a multi-layer perceptron (MLP) is configured and trained for detecting corrosion under above-mentioned real-world illumination scenarios. Training (5000 instances) and validation (2064 instances) datasets for this purpose are generated from the images of corroded steel plates acquired in the laboratory under varying illuminations and shadows, respectively. Each combination of color space and an MLP configuration is individually assessed and the best suitable combination that yields the highest ‘Recall’ value is determined. An MLP configuration with a single hidden layer consisting of 4 neurons (1st Hidden Layer (HL)(4N)) in conjunction with ‘rgb’ color space is found to yield the highest ‘Accuracy’ and ‘Recall’ (up to 91% and 82% respectively). The efficacy of the trained MLP to detect corrosion is then demonstrated on the test image database consisting of both lab-generated partially corroded steel plate images and field-generated images of a bridge located in Moorhead (Minnesota). Lab-generated images used for testing are acquired under varying illuminations, shadows, water wetting, and oil wetting conditions. Based on the validation studies, ‘rgb’ color space and an MLP configuration consisting of single hidden layer with 4 neurons (1st HL(4N)) trained on lab-generated corroded plate images identified corrosion in the steel bridge under ambient lighting conditions.

Slippery liquid‐infused porous surfaces: The effect of oil on the water repellence of hydrophobic and superhydrophobic soils

AbstractSoil wettability is important for understanding a wide range of earth system processes, from agricultural productivity to debris flows and sediment fan formation. However, there is limited research considering how soil–water interactions, where the soil grains are naturally hydrophobic, might change in the presence of oil from natural hydrocarbon leakage or oil spills. Here we show how slippery liquid‐infused porous surfaces (SLIPS) apply to hydrophobic soils, by physical modelling of surfaces of different grain sizes and examining their interactions with water before and after impregnation with silicone oil. Using contact and sliding angle measurements and laser scanning fluorescence confocal microscopy, we demonstrate that soil SLIPS can be created with thick oil layers and thin conformal oil layers on median grain sizes of 231 μm and 32 μm, respectively. Until now, SLIPS have only been observed in human‐made materials and biological surfaces. The mechanisms reported here demonstrate that SLIPS can occur in natural granular materials, providing a new mechanism for water‐shedding in soil and sediment systems. Furthermore, the water‐shedding properties may be long lasting as conformal oil layers are stabilized by capillary forces. These results have important implications for understanding soil physics and mechanics where oil is present in a soil, and for agricultural hydrophobicity on shallow slopes.Highlights We model oil contamination on a hydrophobic model soil as a mechanism for creating SLIPS. Soil SLIPS have implications for water‐shedding, oil spill remediation and earth processes. Our model soils exhibit extreme water‐shedding, illustrated by low water droplet sliding angles. This is the first physical modelling observation of SLIPS arising from hydrophobic soil.

Highly stable superamphiphobic material with ethanol-triggered switchable wettability for high-efficiency on-demand oil–water separation

A large quantity of oil spills occurred have greatly endangered the natural environment and human survival health. Super-wetting materials with switchable wettability provide a good way to solve these problems efficiently and have been paid more and more attention. In this paper, we have successfully prepared an ethanol-triggered and highly stable superamphiphobic material with a switchable surface wettability by using zinc oxide (ZnO) particles and organic silane (PFDS) via a simple coating method. The superamphiphobic material can maintain high oil-repellent and water-repellent performances under various harsh conditions. Most importantly, the superamphiphobic material demonstrates the switchable wettability by ethanol treatment. In view of this fresh mechanism, it can separate various oil–water mixtures on-demand with high separation efficiency and flux. Surprisingly, the mixtures of highly corrosive liquids and oils can also be separated. In addition, the material also has excellent self-cleaning and anti-fouling capabilities and low surface adhesion, which can effectively avoid the pollution of pollutants in the air. All these advantages show that the as-prepared material can play a vital function in solving the related severe conditions of marine oil pollution and industrial wastewater.

In-situ observation of reactive wettability alteration using algorithm-improved confocal Raman microscopy

HypothesisThe wettability of complex fluids on surfaces usually depends on the adsorption of solutes to any of the constituting interfaces. Controlling such interfacial processes by varying the composition of a phase enables the design of smart responsive systems. Our goal is to demonstrate that 3D Confocal Raman Microscopy (CRM) can reveal the mechanistic details of such processes by allowing to simultaneously monitor the contact angle variation and redistribution of the chemical species involved. ExperimentsMotivated by the enhanced oil recovery process of low salinity water flooding, we studied the response of picolitre oil drops on mineral substrates upon varying the ambient brine salinity. The substrates were pre-coated with thin layers of deuterated-stearic acid (surfactant) that display salinity-dependent stability. Findings3D CRM imaging using a recently proposed faster ‘ai’ (algorithm-improved) mode reveals that the surfactant layer is stable at high salinities, leading to preferential oil wetting. Upon reducing the ambient brine salinity, this layer decomposes and the investigated surfaces of mica and – somewhat less pronounced – silica become more water wet. Eventually, the surfactant is found to partly dissolve in the oil and partly precipitate at the oil-water interface. We anticipate that ai-3D-CRM will prove useful to holistically study similar systems displaying reactive wetting.

Comparative study of polypropylene nonwoven on structure and wetting characteristics

In this work, different forms of polypropylene nonwoven sorbents based on the melt-blown method (MB), spun-bond method (SB), and needle punch method (NP) were used as comparative materials. Different forms of polypropylene nonwoven sorbents were evaluated in terms of oil sorption, retention, wetting, and wicking. The analysis indicates that wicking is a result of wetting behavior. Among sorbents, MB possessed higher height for soybean oil and motor oil. Moreover, it takes more time for oil spreading compared with the SB and NP according to different forms of nonwoven sorbents and oil properties. On the other hand, the experimental results revealed that the highest oil sorption and retention were registered by MB, followed by SB and NP. The investigation revealed that different pore sizes, sorbents porosity, and oil properties played an important role in oil sorption performance.

Artificial Diagenesis of Carbonates: Temperature-Dependent Inorganic and Organic Modifications in Reservoir Mimetic Fluids

SummaryWithin reservoirs, spatial variations related to mineralogy and fluid chemistry determine the success of improved oil recovery (IOR) technologies. However, the composition and structure of mineral-adsorbent/fluid interfaces, which fundamentally determine the wettability of reservoir rocks and crude oil (CRO) displacement, are unclear. Replicating the diagenetic alterations of carbonates, this study addresses the temperature dependence of the inorganic and organic modifications of calcite by reservoir pertinent fluids as well as its consequences on mineral wettability and reactivity.We apply a suite of characterization methods, namely confocal Raman, scanning electron, and atomic force microscopy (AFM) as well as infrared spectroscopy, to investigate the modifications of carbonates on aging in formation water (FW), CRO-equilibrated FW, and FW-equilibrated CRO. The microscopic modifications of carbonates show a strong dependence on the aging temperature and are varied, encompassing topographical alterations, substitution of lattice Ca2+ ions by Mg2+ ions and the deposition of particles enriched with polyaromatic hydrocarbons (PAHs) as organic adlayers. Aging in the FWs leads to substantial reconstruction of calcite surfaces, with the deposition of magnesium calcite layers at elevated temperatures. Subsequent aging in FW-equilibrated CRO produces an organic coating on the mineral surfaces, which is composed of PAH-enriched particles. Deposited most strongly at high temperature, these organic layers render contact angles more “oil-wet.” In addition, these layers present a limited permeability for ionic species and substantially reduce the dissolution rates of calcite. The multilayer deposition of organic particles, which thus turns out as a key factor for wettability alteration, is attributed to the interconnected bulk and surface reactions for interfacially active constituents of CRO and the surface precipitation of organo-calcium complexes.Results of this study are relevant to multiple aspects of reservoir development and maintenance, including laboratory scale wettability and coreflooding experiments, and in-silico modeling. The observed nano- and microscopic surface alterations of carbonates within reservoir mimetic environments improve our understanding of the physicochemical relations between mineralogy and fluid chemistry at the mineral-sorbent/fluid interfaces within reservoirs and thereby provide a starting point for the development of novel advanced IOR strategies.

Highly Oil-Repellent Thermoplastic Boundaries via Surface Delivery of CF3 Groups by Molecular Bottlebrush Additives.

We fabricated thermoplastic surfaces possessing extremely limited water and oil wettability without employment of long-chain perfluoroalkyl (LCPFA) substances. Namely, by taking advantage of the structure and behavior of original oleophobic perfluoropolyether (PFPE) methacrylate (PFM) molecular bottlebrush (MBB) additive we obtained polymeric surfaces with oil contact angles well above 80° and surface energy on the level of 10 mN/m. Those angles and surface energies are the highest and the lowest respective values reported to date for any bulk solid flat organic surface not containing LCPFA. We show experimentally and computationally that this remarkable oil repellency is attributed to migration of small quantities of the oleophobic MBB additives to the surface of the thermoplastics. Severe mismatch in the affinity between the densely grafted long side chains of MBB and a host matrix promotes stretching and densification of mobile side chains delivering the lowest surface energy functionalities (CF3) to the materials' boundary. Our studies demonstrate that PFM can be utilized as an effective low surface energy additive to conventional thermoplastic polymers, such as poly(methyl methacrylate) and Nylon-6. We show that films containing PFM achieve the level of oil repellency significantly higher than that of polytetrafluoroethylene (PTFE), a fully perfluorinated thermoplastic. The surface energy of the films is also significantly lower than that of PTFE, even at low concentrations of PFM additives.

Underwater Superoleophobic Surface Based on Silica Hierarchical Cylinder Arrays with a Low Aspect Ratio.

A superantiwetting surface based on low-aspect-ratio hierarchical cylinder arrays (HCAs) was successfully obtained on a silica substrate by colloidal lithography with photolithography. Colloidal lithography is a technique involving transfer of a pattern to a substrate by etching or exposure to a radiation source through a mask composed of a packed colloidal crystal, while photolithography is utilized by which a pattern is transferred photographically to a photoresist-coated substrate, and the substrate is subsequently etched. The surface provides an alternative approach to apply aligned micro-nano integrated structures with a relatively low aspect ratio in superantiwetting. The obtained HCAs successfully integrated micro- and nanoscale structures into one system, and the physical structure of the HCAs can be tuned by modulating the fabrication approach. Using a postmodification process, the underwater–oil wetting behavior of cylinder-array based surfaces can be easily modulated from the superoleophobic state (an oil contact angle (OCA) of 161°) to oleophilic state (an OCA of 19°). Moreover, the underwater–oil wettability can be reversibly transformed from the superoleophobic state (an OCA of approximately 153°) into the oleophilic state (an OCA of approximately 31°) by grafting stimuli-responsive polymer (PNIPAAm) brushes onto this specific hierarchical structure. Due to the temperature-responsive property, modifying the surface with PNIPAAm provides a possibility to control the oil wettability (repellent or sticky) by temperature, which will benefit the use of HCAs in oil–water separation and other application fields.

New scaling model of the spontaneous imbibition behavior of tuffaceous shale: Constraints from the tuff-hosted and organic matter-covered pore system

The volcanogenic tuff layers are widely developed in the organic-rich shale systems of unconventional oil and gas resources. The tuffaceous shale composed of terrigenous detrital components and water-laid tuff is characterized by the complex porous structure related to tuff and organic matter (OM), which hampers the prediction of surface wettability and in-situ oil movability for the tight reservoir. Moreover, the roles of two components in effecting the spontaneous imbibition (SI) behavior remain poorly known. In this current work samples were collected from the Upper Triassic Yanchang Formation of Ordos Basin to set up a novel SI scaling model of tuffaceous shales with the consideration of tuff-hosted and OM-covered pores. The contact angle experiments were conducted to test the wettability of the samples, and spontaneous imbibition (SI) experiments were performed to study the tight oil movability in tuffaceous reservoirs with n-decane. The contents of residual hydrocarbons in the tuffaceous shale were calculated via the Rock-Eval method. Incorporating the above parameters, we proposed a modified scaling model of the SI data considering two specific factors for the tuffaceous shale samples: Factor I of the tuff-hosted pores indicated by the tuff components and Factor II of the organic matter (OM)-covered pores indicated by the residual hydrocarbon contents. The results show that all the tested tuffaceous shale samples are oil-wetting. The imbibition slopes increase with the development degree of the tuff-hosted and OM-covered pores. Notably, zeolite-type minerals, the primary porous components in tuffaceous tight oil reservoirs, contribute the most to the tuff-hosted pores. The long-term interactions between the zeolite mineral surface and residual hydrocarbons notably enhanced the oil wettability of tuffaceous reservoirs and led to a high in-situ oil movability.