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Asphaltene deposition, a widespread challenge in the petroleum industry, detrimentally affects oil production, transport, and processing. Our study investigates asphaltene's impact on sandstone and carbonate reservoir rock wettability using ASTM-D6560 extraction and heptol solutions. A significant part of our focus was to examine wettability change due to asphaltene damage and the use of nanoparticles to improve this situation. Qualitatively, advanced techniques reveal altered rock composition, and contact angle measurements, along with zeta potential assessments, highlight significant wettability changes. Quantitatively, asphaltene-infused solutions induce a quantifiable increase in contact angles. Specifically, with gamma alumina nanoparticle addition, contact angles rise from 68° to 87° for sandstone and 110°–142° for carbonate rocks. Temperature variations within our experimental range also induce notable wettability changes. These findings establish a clear link between asphaltene deposition and quantifiable wettability modifications, providing crucial insights for optimizing oil recovery processes and enhancing well performance in the petroleum industry. The study's results suggest that nano-gamma alumina can be an effective solution for improving wettability and mitigating asphaltene deposition issues in carbonate rocks, offering promising prospects for the oil and gas industry.

Polydimethylsiloxane (PDMS) has attracted great attention in various fields due to its excellent properties, but its inherent hydrophobicity presents challenges in many applications that require controlled wettability. The purpose of this review is to provide a comprehensive overview of some key strategies for modifying the wettability of PDMS surfaces by providing the main traditional methods for this modification and the results of altering the contact angle and other characteristics associated with this property. Four main technologies are discussed, namely, oxygen plasma treatment, surfactant addition, UV-ozone treatment, and the incorporation of nanomaterials, as these traditional methods are commonly selected due to the greater availability of information, their lower complexity compared to the new techniques, and the lower cost associated with them. Oxygen plasma treatment is a widely used method for improving the hydrophilicity of PDMS surfaces by introducing polar functional groups through oxidation reactions. The addition of surfactants provides a versatile method for altering the wettability of PDMS, where the selection and concentration of the surfactant play an important role in achieving the desired surface properties. UV-ozone treatment is an effective method for increasing the surface energy of PDMS, inducing oxidation, and generating hydrophilic functional groups. Furthermore, the incorporation of nanomaterials into PDMS matrices represents a promising route for modifying wettability, providing adjustable surface properties through controlled dispersion and interfacial interactions. The synergistic effect of nanomaterials, such as nanoparticles and nanotubes, helps to improve wetting behaviour and surface energy. The present review discusses recent advances of each technique and highlights their underlying mechanisms, advantages, and limitations. Additionally, promising trends and future prospects for surface modification of PDMS are discussed, and the importance of tailoring wettability for applications ranging from microfluidics to biomedical devices is highlighted. Traditional methods are often chosen to modify the wettability of the PDMS surface because they have more information available in the literature, are less complex than new techniques, and are also less expensive. [ABSTRACT FROM AUTHOR]

Laser surface texturing has attracted growing interest, particularly in functional surface modification. Lasers with nanosecond pulse widths and infrared wavelengths are commonly used for metallic surface texturing because of their low cost and potential for fabricating a large range of textures. In this research, a laser with a nanosecond pulse width and infrared wavelength was used for the surface texturing of 316 stainless steels. Standard grooved and near-isotropic surface textures, as well as novel porous texture and feather-like dendrite texture, were fabricated through single-time laser texturing. Water contact angle tests were performed on the post-process surfaces, and they showed wettability changes from superhydrophilic to superhydrophobic according to different types of textures. Discussion on the relationship between water contact angle and surface roughness, groove width/depth ratio, surface carbon and oxygen contents indicated that it is the surface morphology that impacts changes in wettability. The comprehensive formation mechanism of different textures and the wettability control mechanism through different textures have been systematically discussed. For the first time, the three-level (point-line-area) laser surface ablation mechanism has been established. The proposed findings can be used for future laser texturing process designs on metals using lasers with a nanosecond pulse width and an infrared wavelength for various applications including wettability modification. [ABSTRACT FROM AUTHOR]

Polydimethylsiloxane (PDMS) has attracted great attention in various fields due to its excellent properties, but its inherent hydrophobicity presents challenges in many applications that require controlled wettability. The purpose of this review is to provide a comprehensive overview of some key strategies for modifying the wettability of PDMS surfaces by providing the main traditional methods for this modification and the results of altering the contact angle and other characteristics associated with this property. Four main technologies are discussed, namely, oxygen plasma treatment, surfactant addition, UV-ozone treatment, and the incorporation of nanomaterials, as these traditional methods are commonly selected due to the greater availability of information, their lower complexity compared to the new techniques, and the lower cost associated with them. Oxygen plasma treatment is a widely used method for improving the hydrophilicity of PDMS surfaces by introducing polar functional groups through oxidation reactions. The addition of surfactants provides a versatile method for altering the wettability of PDMS, where the selection and concentration of the surfactant play an important role in achieving the desired surface properties. UV-ozone treatment is an effective method for increasing the surface energy of PDMS, inducing oxidation, and generating hydrophilic functional groups. Furthermore, the incorporation of nanomaterials into PDMS matrices represents a promising route for modifying wettability, providing adjustable surface properties through controlled dispersion and interfacial interactions. The synergistic effect of nanomaterials, such as nanoparticles and nanotubes, helps to improve wetting behaviour and surface energy. The present review discusses recent advances of each technique and highlights their underlying mechanisms, advantages, and limitations. Additionally, promising trends and future prospects for surface modification of PDMS are discussed, and the importance of tailoring wettability for applications ranging from microfluidics to biomedical devices is highlighted. Traditional methods are often chosen to modify the wettability of the PDMS surface because they have more information available in the literature, are less complex than new techniques, and are also less expensive.

To study the effect of acidification on wettability and adsorption characteristics of coalbed methane (CBM), the anthracite in Guizhou mining area was taken as the research object. X-ray diffraction, Fourier transform infrared spectroscopy, contact angle measurement, and isothermal adsorption experiments were carried out successively. Based on the chemical reaction principle, the main acid was determined. The optimum wettability modification conditions were selected using the CRITIC–gray relational analysis method. Moreover, the evolution law of coal wetting modification and CBM adsorption characteristics under acidification was analyzed. The results showed that the main acid of the testing coal sample was hydrofluoric acid, and the optimum wettability modification condition was an acid concentration of 6% and a reaction time of 12 h. After modification, the coal-water contact angle of the testing coal sample decreased by 20.7%, and its wettability was largely enhanced. In addition, the oxygen-containing functional groups of the modified coal samples increased, alkyl side chains decreased, degree of aromatic condensation and aliphatic chain length decreased to varying degrees, and the adsorption of coal sample on CBM weakened. The results of isothermal adsorption experiments showed that the adsorption constants a and b of the modified coal samples decreased by 14.0 and 23.6%, respectively, which further confirms the correctness of the above analysis. The wettability of the testing coal sample was found to be negatively correlated with its adsorption capacity: better wettability correlated to a weaker adsorption capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Adsorption orientation affects the choice of optimal dust suppression surfactant. • Reversal of orientation depends on LUMO and electrostatic potential distribution. • Potential difference and hydroxyl group are the key influencing factors. • Wettability is positively correlated with adsorption orientation. Surfactants are widely used in the field of coal dust control. However, the dust suppression effect of different surfactants varies significantly, and the preferential selection mechanism of dust suppressants for mining is not clear. In this study, the water/surfactant/lignite system was constructed by molecular simulation to investigate the adsorption behavior of surfactants with different structures on the lignite surface at the molecular level. The reasons for the differences in the wettability adsorption of sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), fatty alcohol polyoxyethylene ether-9 (AEO-9), and alkyl polyglycoside (APG1214) on the lignite surface were also investigated based on the quantum chemical calculations and macroscopic experimental analysis. The results showed that the adsorption orientation of surfactant molecules at the solid–liquid interface exerted a pivotal influence on the surface wettability of lignite. According to molecular orbital and electrostatic potential analysis, surfactant molecules with LUMO distributed in the tail chain were more inclined to form a positive adsorption orientation than that concentrated in the polar headgroups; and the stronger the interaction between the polar headgroups and the coal surface with the like charge, the more stable the adsorption of surfactant molecules with the positive arrangement at the interface was. Furthermore, the stronger potential difference between SDS molecules and the hydroxyl-rich structure of the APG1214 molecules are conducive to the formation of hydrogen bonds with water molecules. Wettability experiments showed that the ability of surfactants to improve the wettability of coal dust was positively correlated with the adsorption orientation. [ABSTRACT FROM AUTHOR]

Oil separation from water becomes a challenging issue in industries, especially when large volumes of stable oil/water emulsion are discharged. The present short review offers an overview of the recent developments in the nanofiber membranes used in oily wastewater treatment. This review notes that nanofiber membranes can efficiently separate the free-floating oil, dispersed oil and emulsified oil droplets. The highly interconnected pore structure nanofiber membrane and its modified wettability can enhance the permeation flux and reduce the fouling. The nanofiber membrane is an efficient separator for liquid–liquid with different densities, which can act as a rejector of either oil or water and a coalescer of oil droplets. The present paper focuses on nanofiber membranes' production techniques, nanofiber membranes' modification for flux and separation efficiency improvement, and the future direction of research, especially for practical developments. [ABSTRACT FROM AUTHOR]

Flat micro-Heat Pipe (FHP) provides an excellent solution to the heat dissipation problem of an electronic chip by the gas–liquid two-phase flow. Therefore, the liquid channels and the gas channels are part of the FHP. It determines the performance of the FHP. To this end, these channels were optimized by infiltration modification to accelerate the gas-liquid circulation. In this work, the wick underwent hydrophilic treatment by chemical corrosion and the solutions selected were KOH and (NH4)2S2O8. The shell surface undergoes hydrophobic treatment by electrodeposition with a mixture of zinc-nickel ions. The thermal transfer performance of the Hydrophilic Wick FHP (HW-FHP) and the Hydrophobic Shells FHP (HS-FHP) was analyzed. The results show that the maximum thermal power of the HW-FHP is 10.8 W, 9.1% higher than that of the Untreated FHP (UFHP). The HS-FHP is 11.9 W, 20% higher than that of the UFHP. The HW has a high capillary force, resulting in faster fluid flow. The vapor flow channels made up of the HS have a low resistance to the vapor flow. The hydrophobic surface can reduce the droplet diameter and prevent blocked vapor flow channels. [ABSTRACT FROM AUTHOR]

To alter sandstone rock wettability towards approximately gas wetting state, this study utilized two new types of fluorocarbon-based chemicals. In order to obtain the intensity of wettability modification by spontaneous imbibition tests, static angle measurements, and core flooding which use hexadecane as well as brine, the current study employed a great deal of experiments representing the wettability condition of rock surface. The aim of applying surface characterization approaches, for instance, SEM, EDAX analysis and EDAX map was to consider and approve the adsorption of fluoro-chemical on the rock sample's surface. Respectively, contact angles for brine and hexadecane droplets on the treated surface by RTF solution, after treatment with fluorinated chemical were calculated 144 and 86. The contact angles made by brine and hexadecane droplets with the treated sandstone surface by 86-F solution were 152 and 100, respectively. Due to wettability alteration from highly liquid wet to approximately gas wet condition, spontaneous imbibition test of liquids into the first saturated sandstone core samples by dry air addressed that, before and after treatment, there has been a significant change in the amount of liquid imbibed into the cores. [ABSTRACT FROM AUTHOR]

• Carbonate-rich shale became more oil-wet with the increasing temperature. • Higher CTAB concentration made all the shales more oil-wet. • Higher SDS concentration made clay-/organic-rich shale more water-wet. • Higher SDS concentration had a non-monotonous effect on carbonate-rich shale. Shale wettability affects pore-scale oil/water distribution and reservoir-scale oil extraction efficiency. For enhanced oil recovery, a common method to modify rocks' wettability is adding surfactant. However, previous experiments mainly focused on room temperature conditions, which are not representative of the high-temperature conditions in shale oil reservoirs. Meanwhile, shale consists of various compositions (e.g., clay, carbonate, organic matter), and each composition is expected to have a different influence on shale wettability in a complex way. So far, a comprehensive investigation of shale wettability modification by surfactants and temperature in oil reservoir conditions is still lacking. Therefore, in this work, the effects of temperature (25 ℃ vs 50 ℃), surfactant type (Cetyltrimethylammonium bromide [CTAB] vs Sodium dodecyl sulfate [SDS]) and concentration (0 ∼ 0.2 wt%), and shale compositions (carbonate-, clay- and organic-rich) on shale wettability were investigated systematically via contact angle (θ) measurements in the water-oil-shale system. It is demonstrated that 1) as the temperature increased, the carbonate-rich shale became more oil-wet, no matter the presence or absence of surfactants, while clay- and organic-rich shale became either more oil-wet or more water-wet; 2) At high temperature (i.e., 50 ℃), higher CTAB concentration made all the shales more hydrophobic; higher SDS concentration modified clay- and organic-rich shale more hydrophilic, while had a non-monotonous influence on carbonate-rich shale; 3) At 50 ℃, clay- and organic-rich shale shifted from strongly water-wet to strongly oil-wet with the addition of CTAB, while it became more water-wet with the addition of SDS; carbonate-rich shale became more oil-wet with the addition of CTAB, while it fluctuated erratically with the addition of SDS. This research provides fundamental guidance on wettability modification via surfactant, which has promising applications in EOR in shale oil reservoirs. [ABSTRACT FROM AUTHOR]

Oil separation from water becomes a challenging issue in industries, especially when large volumes of stable oil/water emulsion are discharged. The present short review offers an overview of the recent developments in the nanofiber membranes used in oily wastewater treatment. This review notes that nanofiber membranes can efficiently separate the free-floating oil, dispersed oil and emulsified oil droplets. The highly interconnected pore structure nanofiber membrane and its modified wettability can enhance the permeation flux and reduce the fouling. The nanofiber membrane is an efficient separator for liquid–liquid with different densities, which can act as a rejector of either oil or water and a coalescer of oil droplets. The present paper focuses on nanofiber membranes’ production techniques, nanofiber membranes’ modification for flux and separation efficiency improvement, and the future direction of research, especially for practical developments.

We analyze vacuum storage-assisted transformation of laser-textured aluminum, copper and stainless steel from hydrophilic to hydrophobic state that occurs only in the case of vacuum pump that uses mineral oils and additives. Energy-dispersive X-ray spectroscopy measurements demonstrate an increase in the carbon-containing components on the metals surface with the increase of the storage time inside the vacuum chamber. The alternative storing of laser-treated hydrophilic samples at the conditions when vacuum was obtained using oil-free pumps did not reveal any change in the wettability properties. Reverse transition from the hydrophobic to the hydrophilic state is achieved by annealing only in oxygen-containing environment. We found that low-temperature annealing of as-prepared laser-textured samples in air did not transform the wettability of the hydrophilic metals. [ABSTRACT FROM AUTHOR]

Abstract Although low salinity water injection (LSWI) has recovered residual oil after the conventional waterflood, highly viscous oil has remained in heavy oil reservoirs. Hot water injection is an economic and practical method to improve oil mobility for viscous oil reservoirs. It potentially controls temperature-dependent geochemical reactions underlying the LSWI mechanism and oil viscosity. Therefore, this study has modeled and evaluated a hybrid process of low salinity hot water injection (hot LSWI) to quantify synergistic effects in heavy oil reservoirs. In comparison to seawater injection (SWI) and LSWI, hot LSWI results in more cation ion-exchange (Ca2+ and Mg2+) and more wettability modification. Hot LSWI also reduces oil viscosity. In core-scaled systems, it increases oil recovery by 21% and 6% over SWI and LSWI. In a pilot-scaled reservoir, it produces additional oil by 6% and 3% over SWI and LSWI. Probabilistic forecasting with uncertainty assessment further evaluates the feasibility of hot LSWI to consider uncertainty in the pilot-scaled reservoir and observes enhanced heavy oil production. This study confirms the viability of hot LSWI due to synergistic effects including enhanced wettability modification and oil viscosity reduction effects.

Low-salinity (LS) waterflooding has been a topic of substantial recent interest in the petroleum industry. Studies have shown that LS brine injection can increase oil production relative to high-salinity (HS) brine injection, but contradictory results have also been reported and a mechanistic explanation of these findings remains elusive. We have recently developed a pore-scale model of LS brine injection in uniformly wetted networks (Watson et al. in Transp Porous Med 118:201–223, 2017), and we extend this approach here to investigate the low-salinity effect (LSE) in heterogeneously wetted media. We couple a steady-state fluid displacement model to an innovative tracer algorithm and track the evolving salinity front as oil and HS brine are displaced from the network. The wettability of the pore structure is locally modified where water salinity falls below a critical threshold, and simulations show that this can have significant consequences for oil recovery. Our results demonstrate that, for heterogeneously wetted networks, the oil-wet (OW) pores are the only viable source of incremental oil by LS brine injection. Moreover, we show that a LS-induced increase in the displaced OW pore fraction is a necessary, but not sufficient, condition to guarantee additional oil production. Simulations further suggest that the initial OW pore fraction, the average network connectivity and the initial HS brine saturation are factors that can determine the extent of incremental oil recovery following LS brine injection. This study clearly highlights that the mechanisms of the LSE can be markedly different in uniformly wetted and in non-uniformly wetted porous media. [ABSTRACT FROM AUTHOR]

Displacement of oil droplets receding from solid surfaces in aqueous solutions plays a critical role in many household activities and industrial operations. Surfactants are often involved in these activities to control the displacement process. We hypothesize that the influence of surfactants on the displacement process of oil is highly dependent on the type and dosage of surfactants, with the mechanisms being elucidated by the analysis using appropriate dynamic wetting models. We systematically investigated the spontaneous displacement of a high viscosity oil on curved hydrophilic glass surfaces in aqueous solutions of anionic sodium dodecylbenzene sulfonate, cationic hexadecyl trimethyl ammonium bromide, and nonionic TritonTM X-100 over a wide range of concentrations. The rather different oil displacement behaviors were observed with different surfactant additions. The displacement dynamics of the receding oil droplet was found to be inhibited by surfactant additions and followed two distinct models quantitatively: the power-law model describing the temporal evolution of early-stage displacement, and the molecular kinetic model describing the dependence of the three-phase contact line displacement velocity on the dynamic contact angle at the late stage of oil displacement. The model-based data analysis provided insights on the role of surfactants in controlling the oil displacement dynamics. [ABSTRACT FROM AUTHOR]

Phase change heat transfer allows high heat transfer rates associated with small temperature variations. Given that this technique is employed in several energy and industry applications, such as automotive air-conditioning evaporators, pulsating heat pipes are used for aerospace thermal management and in semiconductor-manufacturing heat exchangers. Although phase change heat transfer has served mankind for more than two millennia, little progress has been made in the last 40 years regarding the basic performance of phase change heat transfer surfaces. However, laser texturing is expected to change this scenario through wettability modification of heat exchanger surfaces, which can lead to heat transfer improvement. In this context, surface texturing of electrolytic copper (a material commonly employed in phase change heat transfer applications) was performed using a nanosecond pulsed fiber laser source associated to a galvanometric scanner. A design of experiments was performed in order to correlate the parameters' pulse overlapping, laser power, number of scanning repetitions, and pulse duration to their respective machining features. Machining depth and width were evaluated, as well as the surface integrity of the processed region. These analyses were performed by means of white light interferometry, optical microscopy, and scanning electron microscopy. The surface integrity analysis is especially important, since there is a lack of information regarding texturing effects on surface properties, as most studies focus almost exclusively on surface topography and not on the thermal effects that laser texturing can promote to the substrate material. After comprehending the parameter effects on the machining features, surface textures were manufactured and evaluated in order to define their effect over surface wettability, which influences the heat transfer performance. Copper oxide present on the laser generated textures granted them hydrophilicity so that most of the tested textures achieved contact angles of 0°. A cleaning process with H2SO4 was proposed to remove this oxide and decrease the wettability, also allowing hydrophobic surfaces with a contact angle up to 180° to be obtained. [ABSTRACT FROM AUTHOR]

The thermal efficiency limitation of the Flat-plate Micro Heat Pipe (FMHP) is a major challenge in the development of the FMHP, where the effect of wick structure and wettability on its thermal performance is studied to improve the thermal efficiency of the FMHP. In this work, a copper spiral woven mesh and copper foam Composite Wick FMHP (CW-FMHP) is designed based on the conventional Copper Foam Wick FMHP (CFW-FMHP), and its thermal performance is analyzed regarding the wick structure and internal gas–liquid two-phase flow characteristics. An oxidized copper spiral woven mesh and copper foam Composite Wick FMHP (OCW-FMHP) has been further developed through the modification of composite wick wettability. The performance tests are carried out with the thermal transfer characteristics of CW-FMHP, OCW-FMHP, and CFW-FMHP under different filling rates and different thermal powers. The experimental results show that the thermal transfer performance of CW-FMHP reaches the optimal under a liquid filling rate of 150%, where the maximum thermal power is 15.7 W, 35.3% higher than that of the CFW-FMHP under the same filling rate. Moreover, the dynamic response characteristics of the CW-FMHP are significantly improved. The thermal resistance of the CW-FMHP is 0.48 °C/W under the filling rate of 150% at the thermal power of 10 W with a reduction of 9.4% compared to the CFW-FMHP under the same condition. Furthermore, the optimal filling rate for OCW-FMHP is lower compared with the CW-FMHP. The maximum thermal power of OCW-FMHP increases to 17.8 W while the thermal resistance reduces to 0.34 °C/W under the liquid filling rate of 140%. This implies that the composite wick structure designed in this work can improve the thermal transfer performance of the FMHP, and the composite wick with wettability modification is more effective regarding both thermal resistance and maximum thermal power.

The hybrid process of carbonated low salinity waterflood (CLSWF) integrating low salinity waterflood (LSWF) and carbonated waterflood (CWF) is proposed as enhanced oil recovery (EOR) incorporating CO2 storage. Based on the understanding of the mechanisms of LSWF and CWF, the hybrid technology is simulated with a fully‐coupled model of fluid flow, geochemical reactions, and equation of state, which describes chemical interactions in the oil/brine/rock system. The comprehensive simulations confirm the synergetic effects of the hybrid CLSWF when compared to waterflooding (WF) and LSWF. In addition, optimum designs of cost‐efficient CLSWF securing CO2 storage are drawn via optimization and sensitivity studies. First, CLSWF enhances wettability modification effect, when compared to LSWF. In CLSWF, extensive mineral dissolution causes more cation exchange. Following the multicomponent ion exchange theory of the wettability modification mechanism, CLSWF produces more residual oil than LSWF with an increasing equivalent fraction of cation. Consequently, it enhances oil recovery by 6.9% and 2.5%, compared with WF and LSWF. Second, the interphase transport of CO2 introduces the oil viscosity reduction effect, which improves the injectivity of CLSWF. Lastly, it sequestrates 25% of the injected CO2 in the depleted reservoir via the solubility‐trapping mechanism. In optimization and sensitivity studies, the optimum design of CLSWF is determined to produce more oil recovery by 9.9% and more net present value by 35% over WF. In addition, 33% of the injected CO2 becomes sequestrated in the reservoirs. This study clarifies that hybrid CLSWF improves EOR, injectivity, and CO2 storage. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Although low salinity water injection (LSWI) has recovered residual oil after the conventional waterflood, highly viscous oil has remained in heavy oil reservoirs. Hot water injection is an economic and practical method to improve oil mobility for viscous oil reservoirs. It potentially controls temperature-dependent geochemical reactions underlying the LSWI mechanism and oil viscosity. Therefore, this study has modeled and evaluated a hybrid process of low salinity hot water injection (hot LSWI) to quantify synergistic effects in heavy oil reservoirs. In comparison to seawater injection (SWI) and LSWI, hot LSWI results in more cation ion-exchange (Ca2+ and Mg2+) and more wettability modification. Hot LSWI also reduces oil viscosity. In core-scaled systems, it increases oil recovery by 21% and 6% over SWI and LSWI. In a pilot-scaled reservoir, it produces additional oil by 6% and 3% over SWI and LSWI. Probabilistic forecasting with uncertainty assessment further evaluates the feasibility of hot LSWI to consider uncertainty in the pilot-scaled reservoir and observes enhanced heavy oil production. This study confirms the viability of hot LSWI due to synergistic effects including enhanced wettability modification and oil viscosity reduction effects. [ABSTRACT FROM AUTHOR]

Abundant oxygen-containing functional groups make lignite high moisture content, which reduces the utilization efficiency of lignite. The decrease in hydrophilicity of lignite surface can be achieved by treating with surfactant. In the present work, two kinds of nonionic surfactants with different hydrophilic groups, n-dodecyl β-D-maltoside (C 12 G 2 ) and dodecyl hepta glycol (C 12 E 7 ), were selected to modify the wettability of lignite surface by molecular dynamics simulation. Because of the drastic differences in compositions and structure of their headgroups, different behaviors were observed. The adsorption results of simulation indicate that polyhydroxy surfactant, C 12 G 2 , adsorbs strongly on lignite surface as a comparison to the poly ether surfactant, C 12 E 7 . However, the extent of hydrophobicity of modified lignite surface by these surfactants is inconsistent with their adsorption capabilities. Compared to the raw lignite, the hydrophilicity of lignite significantly decreases by adsorption of C 12 E 7 , while the C 12 G 2 makes the lignite even more hydrophilicity. The strong polar oxygen-containing functional groups of lignite surface are covered by ethers in C 12 E 7 with weaker polarity, which weakens the interaction between water and lignite. The hydrophilicity of lignite adsorbed C 12 G 2 is strengthened due to the increase in surface polarity by the introduction of polar hydroxyl groups. The results of simulations are in accord with the available experimental data. [ABSTRACT FROM AUTHOR]

Lignite is an important and useful fossil fuel in the world and the strong hydrophilicity of it limits its applications. Surfactant adsorption on lignite is an effective way to make it hydrophobic. In this work, aiming to examine the effect of the degree of ethoxylation on the adsorption behavior of dodecyl poly ethoxylated surfactants on lignite and the wettability modification of modified lignite by surfactant adsorption, different combined systems formed by surfactants, water and a model surface of Wender lignite have been studied using molecular dynamics simulation. The adsorption configurations vary with the degree of ethoxylation. At the same adsorption amounts, increasing the degree of ethoxylation can make the adsorption layer more compactness and bring stronger adsorption strength. The results of binding energy and its components show that the adsorption of alkyl polyoxyethylene ethers surfactant on lignite is physically adsorbed rather than electrostatically or chemisorbed. Meanwhile, van der Waals interaction plays a dominant role in the adsorption. The addition of surfactant could reduce the possibility of the interaction between water and lignite. Compared to the original lignite, the interaction between them is weakened after surfactant adsorption in water/surfactant/lignite system, thus strengthening the hydrophobicity of lignite. Similar to the adsorption strength, hydrophobicity of modified lignite increases with the increase of the degree of ethoxylation. The lignite surface properties are changed due to surfactant adsorption by analyzing the compositions of interaction energy and the change of hydrogen bonds. [ABSTRACT FROM AUTHOR]

The potential of low-salinity (LS) water injection as an oil recovery technique has been the source of much recent debate within the petroleum industry. Evidence from both laboratory and field-level studies has indicated significant benefits compared to conventional high-salinity (HS) waterflooding, but many conflicting results have also been reported and, to date, the underlying mechanisms remain poorly understood. In this paper, we aim to address this uncertainty by developing a novel, steady-state pore network model in which LS brine displaces oil from a HS-bearing network. The model allows systematic investigation of the crude oil/brine/rock parameter space, with the goal of identifying features that may be critical to the production of incremental oil following LS brine injection. By coupling the displacement model to a salinity-tracking tracer algorithm, and assuming that a reduction of water salinity within the pore network leads to localised wettability alteration, substantial perturbations to standard pore filling sequences are predicted. The results clearly point to two principal effects of dynamic contact angle modification at the pore scale: a 'pore sequence' effect, characterised by an alteration to the distribution of displaced pore sizes, and a 'sweep efficiency' effect, demonstrated by a change in the overall fraction of pores invaded. Our study indicates that any LS effect will depend on the relative (scenario-dependent) influence of each mechanism, where factors such as the initial wettability state of the system and the pore size distribution of the underlying network are found to play crucial roles. In addition, we highlight the important role played by end-point capillary pressure in determining LS efficacy. [ABSTRACT FROM AUTHOR]

Reducing coal dust is critical for environmental protection and energy efficiency, however anthracite has a high degree of coalification, high hydrophobicity, resulting in a poor dust removal effect. The addition of surfactants to water can improve the wetting of coal dust, resulting in a more effective dust reduction effect. In this investigation, Polyethylene glycol octyl phenyl ether (Triton X-100) and The lauryl polyoxyethylene ethers (C 12 (EO) 9) were chosen as research subjects. Contact angle experience, Fourier Transform infrared spectroscopy experience (FTIR), and X-ray Photoelectron Spectroscopy experience (XPS) were used to compare the ability of two surfactants to improve the wettability of anthracite from a macro perspective. Molecular dynamics (MD) simulation was used to explain macroscopic experimental phenomena from a microscopic perspective. Due to the presence of the benzene ring structure in the hydrophobic group, the surface of anthracite following Triton X-100 adsorption is more hydrophilic. The network structure of Triton X-100 molecules on the surface of anthracite is loose owing to the presence of the benzene ring, which facilitates water molecule penetration. [Display omitted] [ABSTRACT FROM AUTHOR]

External fluid invading into reservoir could induce formation damage in form of phase trapping in tight sandstone reservoirs (in-situ permeability<0.1 mD). Aqueous phase trapping damage occurs commonly in drilling and completion operations. Once aqueous phase trapping damage happens, it could hardly be removed, as a result of which gas production will not be promising. The objective of this study is to experimentally investigate the wettability alteration by quaternary ammonium fluoride salt and its potential to mitigate aqueous phase trapping damage in original water-wet, tight sandstone gas reservoirs. Wettability alteration from water wetting to gas wetting was achieved as water contact angles on core chip surface treated by 0.1 wt% fluoride were larger than 90° at 27 °C. There was hardly change in contact angles when temperature rose up to 80 °C and 100 °C respectively. The results of contact angle and surface tension tests indicated that the optimal fluoride concentration is 0.1 wt%. Atomic Force Microscope (AFM) analysis revealed that large amounts of fluoride adsorbed on mica surface, forming an irregular micro-nanometer structure. The modified structure enhanced hydrophobicity of surface and promoted the flowback of the invading fluid foreign to reservoir. Fluid rheology tests were carried out by viscometer and the results showed good compatibility between fluoride and drill-in fluid. The result of the core flow test indicated that both the flow back rate and gas relative permeability were significantly improved by 40% and 20% respectively. [ABSTRACT FROM AUTHOR]

Wettability alteration has a positive impact on mitigating the damage caused by water trapping. However, the related mechanisms are not quite clear. In this paper, the use of a quaternary ammonium fluoride salt to alter wettability and its potential to mitigate damage caused by aqueous phase trapping in the original water-wet, tight sandstone was investigated. Wettability alteration from water wetting to gas wetting was achieved after the core samples were treated with fluoride. After treatment, the water contact angles were larger than 90°. These contact angles slightly decreased when the temperature rose to 80 °C and 100 °C. The water surface tension decreased from 71.8 mN/m to 20.7 mN/m with the addition of fluoride and later varied over a small range. The contact angles and surface tension tests indicated that the optimal fluoride concentration was 0.1 wt%. The addition of fluoride slightly increased the viscous shear of the drill-in fluid. The flow back rate of the invading liquid with fluoride (85.1%) was almost double that of the liquid without fluoride (45.2%). With the removal of more water, the gas permeability recovery of cores after the circulation of drill-in fluids with fluoride improved by 20%–30% compared with that of drill-in fluids without fluoride. High performance liquid chromatography (HPLC) tests showed that there was hardly fluoride in the filtrate. The results confirmed that fluoride adsorbed onto the rock when the fluid circulated through the sample. This phenomenon was also proved by scanning electron microscopy (SEM) analysis, which showed that uneven molecular aggregation and amounts of adsorptions were more likely to occur at defect points. The adsorption of fluoride onto the rock surface resulted in a new irregular microstructure with a lower surface free energy, which decreased from 72 mJ/m 2 to 12 mJ/m 2 after fluoride adsorption. The results showed that the modified structure favors water removal. [ABSTRACT FROM AUTHOR]

Numerous core-flooding experiments have shown that low-salinity water flooding (LSWF) could improve oil recovery in sandstone reservoirs. However, LSWF recovery effects remain highly contentious primarily because of the absence of crucial boundary conditions (boundary conditions are defined throughout the paper as the initial and final, contact angle and interfacial tension values). The objective of this paper is to conduct a parametric study using statistical analysis and simulation to measure the sensitivities of LSWF recovery effects in sandstone reservoirs. The summary of 411 core-flooding experiments discussed in this paper highlights the extent and consistency in reporting boundary conditions, which has two implications for statistical analysis: (1) the statistical correlations of the residual oil saturation to chlorite (0.7891) are strong, whereas the statistical correlations of the residual oil saturation to kaolinite (0.4399) contents, as well as to the wettability index (0.3890), are comparably lower, the majority of dataset entries are missing, and no prediction model can be generated; (2) if a prediction model is generated without clay content values and a wettability index, even though LSWF effects emphasizes wettability modification by virtue of oil aging time and the strong influence of brine cation and divalent ion concentrations on Sor, the prediction model's regression curve and confidence level are poor. Reservoir simulations conducted to examine LSWF recovery sensitivities conclude that LSWF recovery effects are governed based on the initial and final wetting states. In all wetting states except for weak water-wet conditions, the increase in oil relative permeability is the underlining recovery effect. In weak water-wet conditions, LSWF incremental recovery is driven by low capillary pressures. In weak oil-wet conditions, the secondary LSWF recovery effect is the change of the non-wetting phase to oil. In all wetting states, an appreciable decrease in interfacial tension (IFT) is realized at the breakthrough recovery. The decrease in IFT is the primary recovery effect in strong water-wet conditions. [ABSTRACT FROM AUTHOR]

The thermal efficiency limitation of the Flat-plate Micro Heat Pipe (FMHP) is a major challenge in the development of the FMHP, where the effect of wick structure and wettability on its thermal performance is studied to improve the thermal efficiency of the FMHP. In this work, a copper spiral woven mesh and copper foam Composite Wick FMHP (CW-FMHP) is designed based on the conventional Copper Foam Wick FMHP (CFW-FMHP), and its thermal performance is analyzed regarding the wick structure and internal gas–liquid two-phase flow characteristics. An oxidized copper spiral woven mesh and copper foam Composite Wick FMHP (OCW-FMHP) has been further developed through the modification of composite wick wettability. The performance tests are carried out with the thermal transfer characteristics of CW-FMHP, OCW-FMHP, and CFW-FMHP under different filling rates and different thermal powers. The experimental results show that the thermal transfer performance of CW-FMHP reaches the optimal under a liquid filling rate of 150%, where the maximum thermal power is 15.7 W, 35.3% higher than that of the CFW-FMHP under the same filling rate. Moreover, the dynamic response characteristics of the CW-FMHP are significantly improved. The thermal resistance of the CW-FMHP is 0.48 °C/W under the filling rate of 150% at the thermal power of 10 W with a reduction of 9.4% compared to the CFW-FMHP under the same condition. Furthermore, the optimal filling rate for OCW-FMHP is lower compared with the CW-FMHP. The maximum thermal power of OCW-FMHP increases to 17.8 W while the thermal resistance reduces to 0.34 °C/W under the liquid filling rate of 140%. This implies that the composite wick structure designed in this work can improve the thermal transfer performance of the FMHP, and the composite wick with wettability modification is more effective regarding both thermal resistance and maximum thermal power. [ABSTRACT FROM AUTHOR]

The cost and environmental effects of most conventional surfactants have increased the search for a greener and cheaper alternative for enhanced oil recovery (EOR) applications. The natural L-amino acids are amphoteric compound with excellent surface properties that have found versatile applications in the pharmaceutical, cosmetic, and food industries. These amino acids exhibited amphipathic nature due to their hydrophobic alkyl chain and charged head. Hence, they could form contacts with both polar and non-polar surface ligands simultaneously. In this study, four amino acids, namely L-arginine, L-lysine, L-methionine, and L-tryptophan, were investigated to access their ability to reduce the interfacial tension (IFT) and alter the wettability of oil-wet sandstone rock. The pendant/rising drop and sessile drop method were employed in IFT and contact angle measurements. The stability of amino acids in brine and the compatibility with other EOR chemicals were tested through visual observation of the precipitates and cloudiness. With the exception of L-tryptophan, the compatibility and stability results revealed that all the amino acids have high salt tolerance above 25 wt% sodium chloride (NaCl). The solutions of amino acids and chemicals such as cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), hydrolyzed polyacrylamide (HPAM), alkali, and alkali-polymer were transparent even at 80 °C. The IFT test results showed that the amino acids significantly reduced the crude oil-water IFT compared to the IFT of n-decane-water system. The IFT between deionized water and crude oil decreased by 76.61% and 55.24%, 24.79%, 45.23% in the presence of L-arginine, lysine, methionine, and tryptophan solutions, respectively. Addition of 0.01 wt% L-arginine, L-lysine and L-methionine to 0.1 wt% SDS reduced the IFT by 28.3%, 15.6%, and 10.97% respectively. The contact angle test showed that L-amino acids have great potential as wettability modifying agents. The contact angles reduced with the decreasing pH (potential of hydrogen) and with increasing brine concentrations from 1 to 4 wt%. Specifically, the contact angle reduced from 92.3°, 91.42°, 89.81° and 92.95 to 47.24°, 53.9°, 58.9° and 59.0° for L-arginine, L-lysine, L-methionine and L-tryptophan, respectively at a pH of about 3. The study suggests that the L-amino acids could be a potential EOR agent in a high saline environment, mainly as a wettability modifier, as well as additives to improve the surface activity of the conventional surfactant and EOR chemicals. Image 1 • Natural L-amino acids such as L-arginine, L-lysine, L-methionine and L-tryptophan were tested as an EOR agent. • L-amino acids have high salt and hardness tolerance and are stable at high temperatures. • L-amino acids reduce the interfacial tension between crude oil and water and enhance the surface activity of surfactants. • L-amino acids have great potential as wettability modifier and hence could be used as an EOR agent. • The performance of L-arginine in reducing the IFT between crude oil and water is quite close to that of SDS. [ABSTRACT FROM AUTHOR]

Reduce the rate of acid-rock reaction is a key problem in the acidizing field. In order to reduce the damage of adsorption of traditional gelled acid in carbonate porous media, and further reduce its damage to permeability of dense carbonate rock after stimulation. Cationic surfactants can change the surface properties of rocks and control the contact area between H+ and rock surface. In order to explore the effect of different carbon chain lengths of cationic surfactants on retarding properties of acid-rock reaction, the critical micelle concentration(C cmc) and critical surface tension value(γ cmc) of seven different carbon chain lengths of cationic surfactants are determined. The results indicate that C cmc decreases significantly with the increasing of carbon chain length. The adsorption morphology of C n TAC(n = 8,10,12,14,16,18,22) species at the solid-solution interfaces is dominated by monolayer. On negatively charged calcite surface, a large number of cationic species RNH 3 + can easily adsorb on abundant CO 3 2− sites, which causes a significant increase of zeta potential for calcite. Meanwhile, the wettability of hydrophilic solid surface is modified from strongly hydrophilic to weakly hydrophilic after adsorption to control the surface rate of acid-rock reaction. The acid solution with a concentration of 1.02 × 10−2 mol/L C 14 TAC has the best retarded performance which the retardation rate is 71.01%. This research is helpful to understand the retarding performance of surfactant, improving the retarded acid system and the effect of carbonate reservoir stimulation. • The ability of different carbon-chain lengths surfactants to modify the rock surface is different. • Longer carbon chain length results in the adsorption morphology change from upright to oblique. • C12 indicates the best retarding effect and lead to the non-uniform etching of rock surface. [ABSTRACT FROM AUTHOR]