Interfacial Tension Behavior Research Articles

Synergistic enhancement of oil recovery: Integrating anionic-nonionic surfactant mixtures, SiO2 nanoparticles, and polymer solutions for optimized crude oil extraction

Enhanced oil recovery (EOR) methods are essential for optimizing oil extraction from modern reservoirs. This research delved into the synergistic impact of combining anionic and nonionic surfactant mixtures with silica (SiO2) nanoparticles (NPs) in sodium chloride (NaCl) solutions, alongside the added enhancement of polymers, to improve crude oil recovery. The study comprehensively evaluated stability, rheological characteristics, interfacial tension (IFT) behavior, wettability alterations, and EOR experiments using mixtures of sodium dodecyl sulfate (SDS) and triton X-100 (TX-100) surfactants. Scenarios both with and without SiO2 NPs in a base solution containing 3000 ppm NaCl and 2000 ppm xanthan gum (XG) polymer were examined. Core flooding tests were carried out on San-Saba sandstone core specimens with low permeability. The stability tests and dynamic light scattering (DLS) analysis were performed to assess the stability of NPs in low saline-surfactant-polymer solution. It was observed that NPs significantly reduced the IFT between the test solutions and crude oil, with nanofluids exhibiting satisfactory stability at a 0.4 wt% SiO2 NPs concentration. Core flooding studies demonstrated a synergistic interaction between NPs and the binary surfactant-polymer mixture, resulting in substantially greater incremental recovery of oil in comparison with the case of using binary surfactant-polymer combination alone. The mechanisms contributing to EOR with nanofluids, such as IFT reduction and wettability alteration, were explored. Incorporating NPs at concentrations of 0.1, 0.2, and 0.4 wt% led to incremental oil recoveries of 4.01 %, 12.35 %, and 12.73 % of the original oil in place (OOIP), respectively, as opposed to the recovery achieved using only SDS + TX-100 + XG. Consequently, these findings advance the understanding of the potential application of SiO2 NPs in combination with the binary surfactant-polymer mixture as effective chemical EOR agents. Additionally, these insights aid in identifying suitable sandstone reservoirs for nanofluid application, contributing to the optimization of oil recovery strategies.

Digital core on a chip: Surfactant flooding in low-permeability reservoir

The development of hard-to-recover reserves every year requires ever-more-innovative industrial and laboratory approaches for efficient production of hydrocarbons. Oil industry has recently turned to the use of microfluidic technology to investigate the flow paths and interactions of reservoir fluids under high pressures and temperatures. The present study describes elaboration of a digital core on a chip, i.e. a microfluidic chip with the structure that replicates the void space of a selected reservoir and is designed based on the computed tomography images of core samples. Similarity of core samples and 2D generated structure was controlled through average pore diameter and structure morphology. The manufactured micromodels were used for surfactant compositions screening aiming to demonstrate the technology capabilities for further testing of various enhanced oil recovery (EOR) chemicals.Thus, several surfactants were examined in bulk employing standard screening procedures (stability evaluation, interfacial tension (IFT) measurements and phase behavior test with oil), and then were investigated in transparent microfluidic chips. Visualization of fluid flow in the porous structure is a primary advantage of microfluidics application for EOR. Hence, surfactant coreflooding-on-a-chip enabled correlation of IFT behavior of various surfactants with recovery efficiency, fast detection of in-situ emulsification and fluid flow distribution analysis in the porous media. Generally, symbiosis of two advanced technologies, i.e. microfluidics and digital core modeling, facilitated significant speed up of laboratory tests and reduce of their cost.

The wetting of H2O by CO2.

Biphasic interfaces are complex but fascinating regimes that display a number of properties distinct from those of the bulk. The CO2-H2O interface, in particular, has been the subject of a number of studies on account of its importance for the carbon life cycle as well as carbon capture and sequestration schemes. Despite this attention, there remain a number of open questions on the nature of the CO2-H2O interface, particularly concerning the interfacial tension and phase behavior of CO2 at the interface. In this paper, we seek to address these ambiguities using abinitio-quality simulations. Harnessing the benefits of machine-learned potentials and enhanced statistical sampling methods, we present an abinitio-level description of the CO2-H2O interface. Interfacial tensions are predicted from 1 to 500 bars and found to be in close agreement with experiment at pressures for which experimental data are available. Structural analyses indicate the buildup of an adsorbed, saturated CO2 film forming at a low pressure (20 bars) with properties similar to those of the bulk liquid, but preferential perpendicular alignment with respect to the interface. The CO2 monolayer buildup coincides with a reduced structuring of water molecules close to the interface. This study highlights the predictive nature of machine-learned potentials for complex macroscopic properties of biphasic interfaces, and the mechanistic insight obtained into carbon dioxide aggregation at the water interface is of high relevance for geoscience, climate research, and materials science.

Integrating low salinity water, surfactant solution, and functionalized magnetite nanoparticles with natural acidic groups for enhanced oil recovery: Interfacial tension study

In recent years, nanoparticles (NPs) have become a popular choice for improving oil recovery through enhanced oil recovery (EOR) methods. NPs can enhance oil recovery by reducing interfacial tension (IFT), altering wettability, and decreasing the mobility ratio. In this study, magnetic NPs with acidic groups (tartaric acid and malic acid), which are natural acids found in fruits such as grapes and apples, were synthesized and functionalized to reduce the IFT between oil and water. Various characterizations tests, including zeta potential (ZP), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), dynamic light scattering (DLS), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray analysis (EDAX), were used to determine the properties of NPs. Afterwards, the IFT behaviour of crude oil and aqueous solutions, containing surfactant sodium dodecyl sulfate (SDS), two types of salts namely sodium chloride (NaCl) and sodium sulfate (Na2SO4), and functionalized magnetite NPs with tartaric acid and malic acid were investigated. Two crude oils were used in this study: light (A) and heavy (B). The results showed that increasing salt concentration decreases the IFT for crude oils down to an optimum point (20000 ppm for both salts), after which the IFT increases with increasing salt concentration. The presence of functionalized Fe3O4@Tartaric acid NPs (300 ppm) in the aqueous solutions containing salts at their optimum concentration (20000 ppm) and SDS (300 ppm) can decrease the IFT more significantly than that of Fe3O4 and Fe3O4@Malic acid for both crude oils. This is due to higher stability and higher ZP of functionalized Fe3O4@Tartaric acid NPs compared to Fe3O4@Malic. The IFT for oil A decreases from 20.8 mN/m to 2.87 mN/m for light crude oil and from 32.96 mN/m to 1.91 mN/m for heavy crude oil. The IFT for heavy crude oil was more reduced than that of light crude oil, which was due to the presence of asphaltene, resin, and other surface-active agents in heavy crude oil, which can act as a natural surfactant in oil and help reducing the IFT.

Chemical separation of petroleum crude oil emulsions using two new poly(ionic liquid)s

AbstractThis work aims to prepare new poly(ionic liquid)s (PILs) and use them for crude oil emulsion separation (EES). PILs were synthesized by an opening ring reaction of hexadecylsuccinic anhydride (HAS) using polyethyleneimine branched MW 600 (PEI) and triethylenetetramine (TTA) in a one‐step procedure, obtaining PILs, HSPI‐PIL, and HSTA‐PIL, respectively. Chemical structure, interfacial tension, aggregate size, and thermal behavior were verified using several techniques. The efficiency of HSPI‐PIL and HSTA‐PIL toward EES was explored using different parameters, including water content (WC), demulsifier concentration, temperature, and pH value. The results indicated that EES proportionally increased with increased WC and temperature. The data also revealed that increased demulsifier concentration improved EES at low WC, for example, 10% and 30%; however, this parameter showed no significant effect with crude oil emulsion containing high WC, for example, 50%. Furthermore, HSPI‐PIL and HSTA‐PIL gave the maximum EES values at a pH of 7, while they decreased in acidic and basic mediums.

Exploring the Effect of Relaxation Time, Natural Surfactant, and Potential Determining Ions (Ca2+, Mg2+, and SO42−) on the Dynamic Interfacial Tension Behavior of Model Oil-Brine Systems

This study examined how the concentration of asphaltene and divalent ions in various salinities affects the interfacial tension (IFT) between a model oil/brine using the pendant drop method. The oleic phase consisted of a mixture of toluene and n-heptane (heptol), to which asphaltene was added to investigate how asphaltene molecules affect the surface properties. The base fluid was prepared with a salinity of 40,000 ppm, and two additional solutions with concentrations of 4000 ppm (low salinity) and 80,000 ppm (high salinity) were created. The results revealed that increasing the concentration of asphaltene within certain salinity ranges led to a decrease in IFT. The lowest IFT was observed at the 40,000 ppm salinity level, indicating that at this optimal salinity, the maximum asphaltene concentration migrated to the heptol/brine interface, reducing the IFT from 23 mN/m to 16 mN/m. Additionally, a 0.5 % wt of asphaltene demonstrated a significant concentration of micellization of natural surfactants, suggesting that the interface was nearly saturated with asphaltene. Consequently, concentrations higher than this value did not significantly alter the IFT. In the final part of the study, the impact of divalent ions was investigated, revealing that as the concentration of Ca2+ ions increased up to fourfold, the IFT decreased to 15 mN/m, about 10 % less than the base case. This value represented the lowest IFT compared to Mg2+ and SO42−. Moreover, modeling the results indicated that the relaxation time decreased with increasing salinity, suggesting that higher salinity accelerated the process of asphaltene absorption at the interface.

Molecular Modeling of the Adsorption of an Egg Yolk Protein on a Water-Oil Interface.

Egg yolk contains several molecular species with emulsifying properties, such as proteins and phospholipids. In particular, these molecules have both polar and nonpolar parts and thus can act as surfactants. One of the most surface-active proteins from egg yolk low-density lipoproteins is the so-called Apovitellenin-1. Experimental studies have been hindered by difficulties in isolating individual species from egg yolk lipoproteins. The purpose of this work was to assess the emulsifying properties of Apovitellenin-1 and any potential cooperative or competitive behavior in the presence of phospholipids. To do so, molecular simulations were carried out in a liquid-liquid interfacial system consisting of water and soybean oil, with varying concentrations of phospholipids and for different spatial configurations. To evaluate the conformational stability of the protein at the water-oil interface, the Gibbs free energy was computed from Metadynamics simulations as a function of the distance from the interface and of the radius of gyration. Moreover, a detailed analysis was also performed to determine which peptide residues were responsible for the protein adsorption at the oil-water interface as well as the lowering of the interfacial tension. Lastly, we combined the simulation results with a thermodynamic model to predict the interfacial tension behavior at increasing protein bulk concentration, which cannot be measured experimentally.

Co-continuous structure enhanced magnetic responsive shape memory PLLA/TPU blend fabricated by 4D printing

ABSTRACT Combining poly (L-lactic acid) (PLLA) with thermoplastic polyurethane elastomer (TPU) can integrate the advantages of excellent biocompatibility and intrinsic shape memory ability of PLLA and high elasticity and excellent shape memory properties of TPU in the application of minimally invasive surgery for bone tissue engineering. However, TPU easily forms a sea-island-like structure in PLLA matrix, decreasing shape memory properties. In this study, a co-continuous structure of TPU phase in PLLA matrix was constructed by adding Fe3O4 nanoparticles due to the changed interfacial tension and flow behavior of TPU, which endowed the TPU/PLLA/Fe3O4 blend fabricated via selective laser sintering (SLS) with excellent shape memory properties. As a result, the morphology of TPU in the blend changed from sea-island-like structure to complete co-continuous structure with increasing Fe3O4 content (0 to 10wt%), and shape recovery ratios in 50 °C water increased from 66.67 to 95.92%. The introduction of Fe3O4 endowed the blend with magnetic responsive shape memory in alternating magnetic field because Fe3O4 could heat it by generating heat from relative friction and particle collisions. Besides, the tensile modulus and hardness of the specimen with 10wt% Fe3O4 nanoparticles increased. In addition, the blend demonstrated excellent biocompatibility by promoting cell adhesion, spreading, and proliferation.

Pore-scale investigation on the flow behavior and oil displacement of ultralow IFT surfactant flooding based on CFD simulation

In order to investigate the flow behavior and oil displacement of ultralow interfacial tension (IFT) surfactant flooding, the experimentally validated computational fluid dynamics simulation model is constructed by coupling the Navier-Stokes equations and the Cahn-Hilliard equation. The mixed surfactant solution is prepared using the ionic liquid surfactant and the nonionic surfactant, and the fluid parameters are measured experimentally. Due to the reduced oil-water IFT, the low pressure drop in porous medium and the decreased oil viscosity, ultralow IFT surfactant contributes to increasing the mobility ability of the fluid front in pores, and its optimal injection velocity is 0.01 m/s. In addition, the sweep area of surfactant flooding in oil-wet porous medium is significantly larger than that of brine flooding because of wettability alteration. Finally, for different porosity models, the residual oil content and the pressure drop of surfactant flooding show a 66.7% and 71.4% decrease than those of brine flooding, respectively, proving its better displacement performance.

Experimental investigation on the effect of interfacial properties of chemical flooding for enhanced heavy oil recovery

Chemical compound flooding has demonstrated its efficacy in enhancing light oil recovery through ultra-low interfacial tension (IFT). However, the optimization of chemical systems properties for displacing heavy oil has not been clarified. This research aims to address this problem by designing common polymer and three surfactant-polymer (SP) systems with varying IFT and interfacial viscoelasticity behaviors, and comparing their ability to recover heavy oil. The findings of core flooding tests indicate that the system with low IFT and high interfacial viscoelasticity simultaneously has a better displacement efficiency for heavy oil than other flood systems, which could enhance heavy oil recovery by 21.94%. Micro-model tests reveal the underlying mechanisms driving the enhanced macro-scale oil recovery. The emulsion formation and interface expansion facilitated by low IFT, as well as increased emulsion stability and reduced snap-off of oil droplets due to the presence of an elastic oil-water interfacial film. These phenomena is more capable of driving microscopic heterogeneous remaining oil and film remaining oil than other solution. The comparative experiment analysis shows that the difference in chemical flooding between heavy oil and light oil is caused by the discrepant distributions of surfactants at the oil-water interface. The light oil interface is a monolayer surfactant molecular film, the heavy components and surfactant moleculars exhibit both competitive and cooperative adsorption phenomena at the oil-water interface. The occurrence of viscosity reduction and increased emulsion stability are more influential factors in the process of heavy oil displacement than those of conventional ultra-low IFT systems used for light oil recovery.

Breakup of thin liquid films with viscous interfaces

Thin liquid films are ubiquitous in nature and have many practical applications. From biological films to the curtain coating process, thin films are present in both large and small scales. Despite their importance, understanding the stability of these films remains a significant challenge due to the fluid–fluid interface that is free to deform, affected by interfacial tension and complex rheological behavior. Instabilities in thin films are often caused by van der Waals attractions, which can lead to the rupture of the layer. To investigate the rupture dynamics, numerical methods are commonly used, such as asymptotic derivations of the lubrication theory or interface tracking methods. In this paper, we present a computational study of the breakup dynamics of a stationary thin liquid sheet bounded by a passive gas with a viscous interface, using the arbitrary Lagrangian–Eulerian method and the Boussinesq–Scriven constitutive law to model the rheological behavior. Our results demonstrate that the stability of thin liquid films is influenced by both surface rheology and disjoining effects and that the viscous character of the interface can delay sheet breakup, leading to more stable films.

Synergistic Effect of Low Salinity Surfactant Nanofluid on the Interfacial Tension of Oil–Water Systems, Wettability Alteration, and Surfactant Adsorption on the Quartz Surface

Interfacial tension (IFT) and wettability are the two major factors influencing oil recovery. The synergistic effect of low salinity water (LSW) with chemical agents such as surfactants, alkalis, and polymer is an emerging technology for enhanced oil recovery (EOR). Recently, the use of nanoparticles for EOR has become the attractive option. This study examines the impact of low salinity surfactant–silica nanofluid (LSS–SNF) on interfacial tension (IFT) and wettability alteration in an oil–water–quartz system using various types of oils, viz., n-heptane, n-decane, benzene, toluene, model oil A, model oil B, and crude oil. Besides, the adsorption of surfactants on the quartz substrate in the presence of silica nanoparticles is also studied. A quartz substrate is particularly chosen to mimic the sandstone formation. It has been observed that the type of oil has a crucial role in the IFT behavior, and different trends have been observed for model oil A and model oil B in the presence of LSS–SNF. Also, a prominent wettability shift is observed on the quartz substrate for the acidic (model oil A) than the other oil employed. Further, the adsorption studies using an ultraviolet–visible (UV–vis) spectrometer confirm the reduction in surfactant adsorption with an increase in silica nanoparticle concentration. The adsorption of surfactants is also confirmed using scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDXA), and the order of adsorption is identical to the Freundlich adsorption isotherm. The outcomes of this study will help us understand the application of silica nanofluid in EOR operation.

Application of a novel surface-active green demulsifier for demulsification of field crude oil emulsion

ABSTRACT In the petroleum industry, generally surface-active chemicals are used to break the crude oil emulsion. But these chemicals are toxic and less biodegradable, which can cause environmental pollution. Therefore, in this paper, eco-friendly demulsifiers (LA1 and LA2) were synthesized by esterification based on fatty acid having low cost and biodegradability. It was characterized by FTIR, NMR, DLS analysis, and TGA. The synthesized demulsifiers were comprehensively characterized by evaluating the micellization parameters such as CMC, Amin, etc. The demulsification performance of synthesized demulsifiers was studied through the static bottle test method. The effect of temperature, demulsifier concentration, pH, settling time, and water content on the demulsification efficiency was thoroughly examined. The result shows that both demulsifiers have excellent surface-active properties. The demulsification mechanism of demulsifiers was elucidated by measuring dynamic interfacial tension and rheological behavior. The bottle test results indicated that the LA1 demulsifier gave 100% separation efficiency at 70°C in 90 min, which performed better than the commercial demulsifier. The present study will give a new route for the eco-friendly and cost-effective treatment of asphaltene-based crude oil emulsion.

Evaluating the Potential of Zwitterionic Surfactants for Enhanced Oil Recovery: Effect of Headgroups and Unsaturation

Surfactants increase the capillary number and resultantly pore-scale displacement efficiency by lowering interfacial tension (IFT) and changing wettability of the rock. However, conventional surfactants precipitate under harsh reservoir conditions such as high temperature and high salinity, thereby limiting their efficiency for oil recovery. As compared to other surfactants, zwitterionic surfactants have good salinity and thermal tolerance. In this work, six in-house developed zwitterionic surfactants with sterling thermal and salinity tolerance were investigated for their behavior at the oleic–aqueous interface. The IFT behavior was investigated by varying the hydrophilic headgroups and the degree of unsaturation in the hydrophobic tail of the surfactants. Additionally, the wettability alteration behavior of the surfactants was evaluated at elevated temperature and pressure. Experimental results depict that the synthesized betaine-type surfactants demonstrated exemplary stability and efficiency for EOR. The surfactants reduced the IFT at the oleic–aqueous interface and changed the wettability of carbonate porous media toward aqueous-wetting conditions. The surfactant headgroup influenced wettability alteration behavior in the order hydroxysulfonate > sulfonate > carboxy group. Meanwhile, the introduction of unsaturation decreased the surfactant wettability alteration behavior. Finally, oil recovery results from the spontaneous imbibition experiment on carbonates depict that the zwitterionic surfactants recovered 31.3–44.1% OOIP.

Surfactant formulation development for shallow reservoirs with high clay content

Sandstone reservoirs with high clay content can potentially adsorb large amounts of surfactants making the chemical flood processes unattractive. The objective of this work was to develop an alkaline-surfactant-polymer (ASP) process for a shallow, clayey sandstone reservoir to minimize surfactant retention. The phase behavior study was conducted to identify commercially available surfactants that display ultralow interfacial tension behavior. The selected surfactant formulations were tested in tertiary ASP core floods in outcrop and reservoir rocks. Many surfactant formulations were identified which gave ultralow IFT, but the formulation with only one surfactant (at 0.5 wt% concentration) in presence of one co-solvent was selected for core floods. The cumulative oil recovery was in the range of 92–96% of the original oil in place (OOIP) in the core floods. The surfactant retention was low (0.15 mg/gm of rock) in spite of the high clay content due to the use of alkali. The study showed that 0.5 PV of ASP slug and 2700 ppm of the polymer were required to make the flood effective. Injection of the ASP slug immediately after the field brine flood with divalent ions did not cause any plugging or adverse effect. The novelty of this work lies in designing ASP formulations with a single surfactant and reducing the residual oil saturations to ∼3% in field cores along with low surfactant retention. This paper illustrates a workflow to identify the chemical formulation, chemical concentrations and slug sizes.

Modeling of Interfacial Tension and Inclusion Motion Behavior in Steelmaking Continuous Casting Mold.

The current work is an expansion of our previous numerical model in which we investigated the motion behavior of mold inclusions in the presence of interfacial tension effects. In this paper, we used computational fluid dynamic simulations to examine the influence of interfacial tension on inclusion motion behavior near to the solid-liquid interface (solidifying shell). We have used a multiphase model in which molten steel (SPFH590), sulfur, and alumina inclusions have been considered as different phases. In addition, we assume minimal to negligible velocity at the solid-liquid interface, and we restrict the numerical simulation to only include critical phenomena like heat transport and interfacial tension distribution in two-dimensional space. The two-phase simulation of molten steel mixed with sulfur and alumina was modeled on volume of fluid (VOF) method. Furthermore, the concentration of the surfactant (sulfur) in molten steel was defined using a species model. The surfactant concentration and temperature affect the Marangoni forces, and subsequently affects the interfacial tension applied on inclusion particles. It was found that the alteration in interfacial tension causes the inclusion particles to be pushed and swallowed near the solidifying boundaries. In addition, we have compared the computational results of interfacial tension, and it was found to be in good agreement with experimental correlations.

Formulation for chemical EOR: Development and evaluation of an ASP formulation In customer field conditions

AbstractAlkali surfactant polymer (ASP) flooding is an enhanced oil recovery (EOR) technology with an impressive potential for increasing incremental oil production from conventional hydrocarbon bearing reservoirs. A challenge to ASP application is the complexity of determining an effective formulation, typically requiring extensive laboratory screening of nearly countless combinations of surfactants and cosolvents. This paper focuses on demonstrating the utility of the hydrophilic–lipophilic deviation (HLD) concept for EOR application to simplify surfactant formulation workstreams seeking an economically viable ASP formulation for field application. In describing work performed for EOR application of ASP under customer conditions using crude oil, the discussion covers the initial evaluation of the promising surfactant formulation (interfacial tension and solubility), the improvement upon the formulation via HLD principles, and the evaluation of the improved surfactant formulation (coreflood studies). The final ASP formulation identified consisted of a 9 to 1 mixture of alkyl propoxy sulfate sodium salt (APS) to alkyl ethoxy sulfate sodium salt (AES) totaling 2000 ppm active surfactant content, 2.0 wt% Na2CO3, and 3000 ppm polyacrylamide polymer (all commercially available products). This formulation had ultra‐low interfacial tension and favorable mixing behavior under reservoir conditions. In coreflood studies, the final formulation reproducibly achieved cumulative oil recovery of 96.4%–98.5% of original oil in place with only 0.3 PV of ASP injection with a chase alkali polymer injection.

Toward mechanistic understanding of interfacial tension behavior in nanofluid-model oil systems at different asphaltene stability conditions: The roles of nanoparticles, solvent, and salt concentration

Surface phenomena between liquid-liquid phases like interfacial tension (IFT) can significantly affect the recovery factor in hydrocarbon reservoirs. Nanotechnology could be used as a chemical method for enhanced oil recovery (EOR) via IFT reduction and wettability alteration. Nanoparticles could draw the asphaltene molecules to the interface of crude oil and brine water to reduce IFT. Several researches were conducted on SiO2 nanoparticles due to their accessibility with low price and their good performance in wettability alteration. However, the mechanism of IFT changes under different conditions of asphaltene instabilities and in the presence of nanoparticles has not been fully understood yet. In this study, the stability of SiO2 nanofluid in the presence of different NaCl concentrations was evaluated by visual observation, spectral analysis, and measuring the size of the hydrodynamic diameter of the particles. Besides, Fourier transform infrared (FTIR) spectroscopy of asphaltene was measured. Then, the influence of different parameters, including asphaltene content, water salinity, and nanoparticle concentration on the IFT between synthetic oil and nanofluids, was measured by the pendant drop shape method using drop shape analysis apparatus. Furthermore, IFT changes due to asphaltene instability at different n-heptane content and the instabilities of SiO2 nanoparticles at higher salinities were discussed. The IFT between synthetic oil and brine was measured. Results showed that the IFT reduces (about 23 mN/m) at very high salt concentrations due to the presence of free salt ions attracted with the hydrocarbon phase. Also, increasing the instability of asphaltene to a particular n-heptane concentration reduces the IFT variation by NaCl concentration from 5 mN/m to 2.5 mN/m because less potential remains for asphaltene adsorption at the interface. In addition, the increase in n-heptane concentration leads to a decrease and then an increase in IFT. Furthermore, as the nanoparticles become unstable at high salinities, the IFT increases significantly. Moreover, the IFT difference between the case with nanoparticle and the case without it is about 20 mN/m.

An Overview of the Oil+Brine Two-Phase System in the Presence of Carbon Dioxide, Methane, and Their Mixture

An overview of the molecular simulation studies of the oil+brine two-phase system in the presence of CO2, CH4, and their mixture at geological conditions is presented. The simulation results agreed well with the experimental results and the density gradient theory predictions on the basis of the cubic–plus–association equation of state (CPA EoS) (withDebye–Hückel electrostatic term) and the perturbed chain statistical associating fluid theory (PC-SAFT) EoS. The interfacial tension (IFT) of the alkane+H2O system showed almost a linear increase with an increasing number of carbon atoms in the alkane molecule. These IFTs are approximately equal for linear, branched, and cyclic alkanes. Here, the negative surface excess of the alkanes might explain the increase in the IFTs with an increase in the pressure. The surface excesses of the alkanes increased with decreasing temperature. This may explain the decrease of the slopes in the IFT versus pressure plot with a decrease in the temperature. The IFT behavior of the alkane+water+CH4/CO2 system was found to be similar to that observed for the alkane+water system. The addition of CO2 had a more significant influence on the IFT than the addition of CH4. Here, CH4 and CO2 exhibited a positive surface excess. The negative surface excess of the salt ions probably explains the increase in the IFTs of the alkane+brine system with increasing salt content. The solubilities of CH4 and/or CO2 in the H2O-rich phase of the alkane+brine+CH4/CO2 system increased with decreasing salt content (salting-out effect). The IFT of the aromatic hydrocarbon+H2O system is much lower than that of the alkane+H2O system. The surface excess followed the order o-xylene > ethylbenzene > toluene > benzene for the aromatic hydrocarbon+H2O system. This trend has a direct correlation with the aromatic–aromatic interaction.

Synthesis and performance evaluation of polymeric surfactant from rice husk and polyethylene glycol for the enhanced oil recovery process

A tertiary recovery technique is needed to recover the remained oil in the oil field after primary and secondary recoveries, which can only recover approximately 30–50% of the total oil. This study investigated the synthesized polymeric surfactants from rice husk and polyethylene glycol (PEG) for the enhanced oil recovery (EOR) process as a tertiary recovery technique. The rice husk was used as sodium lignosulfonate (SLS) surfactant production feedstock. SLS-PEG polymer surfactant from rice husk has not been widely studied, especially for the EOR process. This study has comprehensively investigated the effect of PEG concentration on the polymeric surfactant properties. The surfactants were characterized using Fourier transform-Infrared (FT-IR) analysis. Several other tests were also conducted, including surfactant compatibility, viscosity, thermal stability, interfacial tension (IFT), and phase behavior. It was found that the PEG introduction to the SLS surfactant could increase the hydrophilic property of the polymeric surfactant due to the presence of the C−O−C group. In addition, the IFT value decreased with the increase in the PEG concentration due to the increase in the hydrophilic property. However, the IFT value decreased when the PEG concentration was too high. The lowest IFT value was obtained at the SLS to PEG ratio of 1:0.8. It produced the highest increase in the additional recovered oil after brine flooding. The results showed that the rice husk, which is agricultural waste, could be utilized as a feedstock for the surfactant production.