Interfacial Tension Of Crude Oil Research Articles

Development of an in situ emulsifying/ultra-low-interfacial-tension cyclic flooding system for medium- and low-permeability reservoirs

Medium- and low-permeability reservoirs are important in oilfield development. However, due to their characteristics of poor pore permeability and high heterogeneity, the development of suitable technologies has been very difficult. In this study, an in situ emulsifying/ultra-low-interfacial-tension cyclic flooding system has been developed for low- and medium-permeability reservoirs. Based on the hydrophilic-lipophilic balance (HLB) value method, an emulsifying surfactant ASD with Span 80 (sorbitan monooleate) as the main component has been identified as highly promising through screening. At mass fractions of surfactant ASD between 0.2% and 0.6%, the extent of water separation from the emulsion is greatly reduced, and the W/O emulsion can effectively improve the mobility ratio and increase the sweep volume. The surfactant SA synthesized in our laboratory reduces the interfacial tension of crude oil to 10−4 mN m−1. Laboratory core flooding experiments have shown that multiple rounds of alternating injection with aqueous solutions of surfactants ASD and SA can improve oil recovery by 22.25%. Upon injecting a low-viscosity aqueous solution of surfactant ASD, it emulsifies crude oil in situ under reservoir conditions, solving the problems of difficult polymer injection and insufficient spread. Our work provides useful insights for the development of low- and medium-permeability reservoirs.

Effect of CO2 on the interfacial tension and swelling of crude oil during carbonated water flooding

Since the influence of carbon dioxide (CO2) on the dynamic interfacial tension of crude oil and aqueous solutions at the elevated temperatures and pressures is an important issue, this investigation is aimed to measure the IFT of crude oil/water, CO2, and carbonated water. The measured values reveal that the IFTs of crude oil/CO2 are decreased through the first interval, while a gradual and continuous reduction in IFT is obtained at the second interval. Although both intercepts and slopes of the first interval lines are more than the second interval for all the studied temperatures, they show a similar trend as a function of temperature. The used vanishing IFT method measurement reveals that the minimum miscibility pressure (MMP), first contact miscibility pressure, and intersection point (where the slopes of the linear curves change) of two linear equations have a linear increasing trend as temperature changes. However, this trend was not observed for the aqueous solution saturated with CO2 (i.e., carbonated water) which can be related to the difference between liquid- and gas-phase behavior as well as the formation of carbonic acid in the carbonated water process. IFT values reduced from 18.6 mN/m (@ pH = 8) to 0.3 mN/m (@ pH = 14) with an increase in pH of the aqueous solution, while miscibility conditions can be obtained for CO2 cases at pressures higher than the MMP points. Considerably higher IFT values were measured in the presence of water and carbonated water in the range of 9.1–17.5 mN/m and 12.2–17.4 mN/m, respectively. The most important feature of the CW process can be the swelling factor of crude oil due to the fact that the oil swelling of up to 40% was achieved at elevated temperature (75 °C) and pressure (4500 psi) after only1600 s.

Performance evaluation of silica nanofluid for sand column transport with simultaneous wettability alteration: An approach to environmental issue

The most promising method to improve chemical oil recovery via wettability alteration is associated with colloidal solution such as nanofluid. However, nanofluids show limitations due to nanoparticle agglomeration which may result into pore blockage during its injection in a porous media. The unsuccessful recovery of injected nanoparticles has increased their footprints, which is becoming a serious environmental issue. Therefore, this study reports the use of a co-stabilizer i.e. TiO2 (0.05 and 0.1 wt%) that not only reduces nanoparticle agglomeration in silica nanofluid (SiO2, 0.5 wt%) but also improves its wetting property and oil recovery from synthetic sand-packs of porosity = ∼29–33% and permeability = ∼700–800 mD. In nanofluid synthesis, polymer polyacrylamide was used as base fluid and surfactant [anionic: sodium dodecylsulfate and nonionic: triton x 100] was used to find improvements in wettability alteration, interfacial tension reduction, and oil recovery results of nanofluid. With surfactant, the wetting property of STN (SiO2–TiO2 nanofluid) was found superior (strong water-wet) as confirmed by maximum (67%) reduction in contact angle. Also, interfacial tension of crude oil reduced by ∼91% which increased the chemical oil recovery by ∼78% from sand-pack. Importantly, nanofluid use in porous media is associated with environmental concern. Therefore, each nanofluid was repetitively (3 times) flooded through sand-pack and NP retention was examined using three different characterization methods (contact angle, ultraviolet visible, and field emission scanning electron microscopy) and suitably compared to find least nanoparticle retention in porous media. For surfactant treated nanofluids, nanoparticle retention of 0.03–0.07 wt% was determined while its value was significantly higher (0.31 wt%) for conventional SiO2 nanofluid. Finally, this study suggests that nanoparticle retention of conventional silica nanofluid can be reduced through the selection of a proper co-stabilizer that may help to protect subsurface from pore blockage and other associated environmental issues.

Continuous monitoring of crude oil movement in an electromagnetic-assisted enhanced oil recovery process using a modified fiber Bragg grating sensor

The Fiber Bragg grating (FBG) sensor used for distinguishing the oil movement offers detailed insights about the reservoir oil and is the key to quantifying the impact on improvement and the integrity and efficiency of the wells. The modified FBG sensors proposed in this paper through a partially un-cladding process and magnetostrictive nanolayer coating could advantageously monitor the crude oil mobility in electromagnetic-assisted enhanced oil recovery operations. The remaining ∼400 nm thickness of cladding after partial removal was coated with ∼100 nm magnetostrictive Ni-Fe nanolayer. The structures of Ga-doped magnetite and Ga-doped hematite were found orthorhombic with Pnma space group and rhombohedral with R3C space group, with the corresponding remnant magnetization (retentivity) value of 94 Oe and 150 Oe, respectively. The magnetization values at 1.5 T were 30 for Ga-doped magnetite and 21 emu/g for Ga-doped hematite nanoparticles. The interfacial tension of crude oil and brine dropped for 16.9 % and 4.1 % when the Ga-doped magnetite and the Ga-doped hematite nanofluid were injected, respectively. The correlated contact angle for the Ga-doped magnetite was 65.2˚, while for the Ga-doped hematite, it was 57.4˚. The FBG’s responses to different nanofluids and surfactant injection at the presence of electromagnetic field indicated the high sensitivity of the probe against the induced magnetic field, which was varied as a function of distance, nanofluids type, and nanoparticles accumulation near the FBG sensing point. The increase in the wavelength shift of FBG by flowing the nanofluids through the sandstone and opposite behavior was recorded by surfactant flowing. The maximum wavelength shift was 0.21 nm when Ga-doped magnetite nanofluid was injected, whereas it was 0.14 when Ga-doped hematite was injected.

Effect of CO2/N2 Mixture Composition on Interfacial Tension of Crude Oil.

CO2-enhanced oil recovery (EOR) has demonstrated significant success over the last decades; it is one of the fastest-growing EOR techniques in the USA accounting for nearly 6% of oil production. A large quantity of CO2 gas is required for the EOR process and sometimes other gases such as hydrocarbons, air, flue gases, CO2, N2, and mixtures of two or more gases are used for injection. It is also realized that the injection of CO2 and N2 combines advantage in reducing CO2 concentrations in the atmosphere and improving the oil recovery by sequestering it underground. However, there are a number of variables involved in the successful design of the CO2-EOR process. The objective of this study is to investigate the effect of CO2/N2 mixture composition on interfacial tension (IFT) of crude oil. Experiments were performed to measure the IFT of the CO2/N2 mixtures and crude oil for different compositions of gas by varying the system pressure at a fixed temperature. The effect of CO2/N2 mixture composition and pressure on the IFT of crude oil is evaluated. The experimental results show that an increase in the mole fraction of CO2 in the gas mixture results in a decrease in IFT between CO2–oil, irrespective of the system pressure. However, because of an increase in the mole fraction of N2 in the gas mixture, an increase in IFT was observed and this change is opposite to the effect of the CO2 mole fraction. Also, the change in IFT is consistent with the pressure, which means that the IFT decreases with an increase in the pressure at a given temperature. The effect of the CO2 mole fraction is more profound compared to the N2 fraction and with the pressure at which experiments were conducted in this study. The finding of this study helps in designing the CO2-EOR process in which achieving miscibility conditions is vital for taking advantage of the CO2 injection. Also, the presence of N2 and its influence on the IFT that must be considered in the CO2-EOR were addressed in this study.

Structure-activity relationship of anionic-nonionic surfactant for reducing interfacial tension of crude oil

In this article, we have investigated interfacial tensions (IFTs) of anionic-nonionic surfactant fatty alcohol polyoxyethanol carboxylate (CnEOmC) and their mixed solutions against n-alkanes, crude oil and model oils containing crude oil fractions, such as saturates, aromatics, resins and asphaltenes. The experimental results show that EO group plays a crucial role in reducing IFT by adjusting the area occupied for CnEOmC molecules at the interface and only surfactant with optimum EO number produces lower IFTs against n-decane, named size compatibility. The hydrophilic-lipophilic balance is another important factor for reducing IFT. Ultralow IFT value can only be achieved when both hydrophilic-lipophilic balance and size compatibility are met simultaneously. Fortunately, one can adjust the hydrophilic-lipophilic balance and keep size compatibility simultaneously by mixing CnEOmC with different EO numbers to produce ultralow IFTs for both hydrocarbons and crude oil. Moreover, the spaces with different sizes occur at the mixed adsorption film. As a result, we can observe synergism between model oils containing resins, aromatics or asphaltenes during wide concentrations and mixed solution of C14EO3C and C14EO7C with mass fraction ratio of 1:1. This may be another reason for the ultralow IFT values of mixed solutions against crude oil. The mechanism provided in this paper is very important for the design of chemical flooding at high salt reservoir conditions.

Functional microbial stimulation for oil recovery enhancement based on microbial community analysis

This study stimulated functional microbial adaptation to the extreme environment of the Luliang oilfield reservoir and assessed the impact of indigenous microbial enhanced oil recovery treatment on the microbial community and oil recovery. By high-resolution pyro-sequencing, Acinetobacter, Pseudomonas, Sphingomonas, Thauera, Arcobacter and Hyphomonas were regarded as suitable candidates and a customised nutrient mixture was selected to activate the target microbes. The interfacial tension of crude oil and water decreased from 29.76 mN m−1 to 0.65 mN m−1 and the emulsion stability index increased from 5% to 92% after customised nutrient culture. The oil biodegradation experiments after the cultivation exhibited positive effects in degrading aromatics, resins and asphaltenes fractions and improving the mobility. Six target genera were activated markedly after 96 h of incubation. The oil recovery was enhanced from 51.2% to 60.7% using fermentation broth injection. Thus, injecting a customised nutrient mixture with injection brine into the stratum to stimulate functional microbes has the potential to enhance oil recovery in the Luliang oilfield.

The Initial Comparison Study of Sodium Lignosulfonate, Sodium Dodecyl Benzene Sulfonate, and Sodium p-Toluene Sulfonate Surfactant for Enhanced Oil Recovery

Surfactant (surface active agent) exhibit numerous interesting properties that enable their use as additional component in mobilising of residual oil from capillary pore after secondary recovery process using gas injection and water flooding. In this study, Sodium Lignosulfonate (SLS) surfactant was successfully synthesized by applying batch method using lignin from oil palm empty fruit bunches as precursor. Furthermore, its performance in reducing interfacial tension of crude oil and formation water colloidal system was compared with commercial available surfactant including Sodium Dodecyl Benzene Sulfonate (SDBS) and Sodium p-Toluene Sulfonate (SpTS). The synthesized SLS surfactant was characterized by using Fourier Transform Infrared (FTIR) spectroscopy. Meanwhile, its performance in reducing interfacial tension of crude oil and formation water colloidal system was analyzed by using compatibility test, phase behaviour analysis, and interfacial tension (IFT) measurement. The compatibility test shows that SLS, SDBS, and SpTS surfactants were compatible with formation water. In addition, the phase behaviour analysis shows that SLS surfactant was better than SpTS surfactant, while SDBS surfactant generates the highest performance proved by the best microemulsion formation resulted by SDBS. Furthermore, the optimum concentration of SLS, SDBS, and SpTS surfactants in reducing the interfacial tension of crude oil and formation water was 1.0%. The IFT measurement indicates that the performance of SLS with the value of 1.67 mN/m was also better than SpTS surfactant with the value of 3.59 mN/m. Meanwhile, SDBS surfactant shows the best performance with the IFT value of 0.47 mN/m.

Effects of asphaltene, resin and crude oil type on the interfacial tension of crude oil/brine solution

In recent years, the behavior of crude oil interfacial tension (IFT) as a function of salt concentration have been investigated. The results found in literature are highly controversial, thus the current experimental study aimed to clarify the reasons behind this by developing a methodology based on extracting asphaltene and resin from three different crude oils and performing elemental analysis on them. In addition, the effect of salinity on the IFT of three studied crude oil was compared with the synthetic crude oil consisted of different weight percent (wt%) of asphaltene and resin in toluene. The obtained results revealed that the IFT of crude oil as a function of salinity depended not only on the wt% of asphaltene and resin fractions but also on the aromaticity of asphaltene and resin. In fact, as the aromaticity of asphaltene increased, the performance of asphaltene decreased as a function of salinity while the aromaticity of resin led to a revers trend on IFT variation.

The effects of pH, acidity, asphaltene and resin fraction on crude oil/water interfacial tension

A basic understanding of the activities of indigenous surfactants of crude oil at the water/oil interface as a function of aqueous phase pH can give us a better insight into the alkaline enhanced oil recovery processes. The present study aimed to elucidate the effect of salinity and crude oil type, specifically the influence of resin and asphaltene molecules during alkaline flooding through interfacial tension (IFT) measurements via pendant drop and spinning techniques. Several model oils containing asphaltene and resin fractions were prepared and their IFTs were compared with those of the original crude oils. Moreover, the elemental analyses of asphaltene and resin fractions were performed, and the total acid numbers of all oils were measured as well. The IFT results of three studied crude oils and the asphaltenic and resinous model oils with sea water and deionized water underlined the importance of the degree of salinity, and qualitative and quantitative nature of resin and asphaltene fractions. It was also revealed that the amount of asphaltene and resin fractions as well as their structural nitrogen and oxygen contents were the most influential parameters on the IFT of crude oil as a function of pH values. In addition, the variations of IFT crude oils/the ionic solution and deionized water were more noticeable in the basic aqueous solutions.

Emulsifying action of Pseudomonas aeruginosa L6-1 and its metabolite with crude oil for oil recovery enhancement

ABSTRACTPseudomonas aeruginosa L6-1 was isolated from formation brine of Xinjiang Oilfield, China. Strain L6-1 showed perfect emulsification activity to crude oil and transformed mixture of crude oil and water into emulsion when crude oil was used as sole carbon source; thus, this method is a promising approach for emulsification and mobilization of residual oil in oil reservoirs and enhancement of its recovery. Average diameters of emulsified crude oil were between 1 and 8 µm. Interfacial tension of crude oil and water was reduced to 0.8 mN m−1. Strain L6-1 produced 2.2 g L−1 of rhamnolipid biosurfactant. Core flooding tests were carried out to investigate application potential of strain L6-1 for microbial enhanced oil recovery (MEOR). Enhanced oil recovery efficiencies ranged from 9.23% to 12.58% in both core models, with and without oxygen injection. These results revealed that strain L6-1 is a candidate functional microorganism for MEOR application.

The influence of spreading coefficient on carbonated water alternating gas injection in a heavy crude oil

The interfacial properties change strongly with temperature and pressure that could influence the displacement of fluids in porous media. The main objective of this study was to measure interfacial tension (IFT) of the binary systems of brine/crude oil/carbon dioxide (CO2) and carbonated brine/crude oil/CO2 at two temperatures and different pressure conditions. Spreading coefficient (SC), which is determined from IFT data, is an important parameter in enhanced oil recovery (EOR) methods, which are based on three phase systems. The spreading or non-spreading (the oil creates to form an immobile half sphere) oil on the water–gas interface is a key factor on determining residual oil saturation during water alternating gas (WAG) injection process. In this work, experimental results on oil swelling and interfacial tension of crude oil, brine/carbonated brine and carbon dioxide systems at the pressure range of 2.76–13.79MPa and two temperatures of 40°C and 50°C is presented. Afterwards, by estimating spreading coefficient of the mentioned systems an optimum condition for the enhanced oil recovery (EOR)-WAG process is proposed.The results indicate that, the equilibrium IFT data of the carbonated brine–crude oil system is lower compared to that of the brine–crude oil system at the same conditions. The interfacial tension of the carbonated brine–crude oil system decreases significantly at higher pressures. In addition to IFT reduction due to the presence of CO2 in water, oil swelling was also observed. In this experimental work, the dynamic oil swelling was monitored as a function of time. The IFT data of the above systems were also used to estimate the spreading coefficient as a function of pressure at both temperature conditions. The estimated spreading coefficient data for the brine/crude oil/CO2 and carbonated brine/crude oil/CO2 systems, indicates that the presence of CO2 in the brine phase, makes the spreading coefficient positive, while this parameter in the brine/oil/CO2 system is negative. This means that oil would be spread on the water phase during carbonated water alternating CO2 injection that consequently could further enhance oil recovery.

Mechanistic study on the dynamic interfacial tension of crude oil + water systems: Experimental and modeling approaches

This study investigates dynamic interfacial tension (DIFT) of acidic crude oil (ACO) and non acidic/basic crude oils (BCO)+deionized water (DW) as a function of pressure from 500 to 4000psi, and temperature from 30 to 80°C using an axisymmetric drop shape analysis (ADSA) technique. DIFTs are also modeled using dynamic adsorption model, mono-exponential decay model, and empirical equations. The results showed that if a reduction in the surface excess concentration due to increasing temperature overlooks the total entropy of the molecules in the system, an increase in IFT would be expected.

Effect of different families (imidazolium and pyridinium) of ionic liquids-based surfactants on interfacial tension of water/crude oil system

Interfacial tension between crude oil and water plays a significant role in enhanced oil recovery. Many researchers seek surfactants to reduce the interfacial tension of crude oil and water that can be applicable in reservoir conditions of high salinity and temperature. The current study introduces the results of using two different families of ionic liquids (ILs) including imidazolium (1-dodecyl-3-methylimidazolium chloride ([C12mim][Cl]) and 1-octyl-3-methylimidazolium chloride ([C8mim][Cl])) and pyridinium (1-dodecyl pyridinium chloride ([C12Py][Cl]) and 1-octyl pyridinium chloride ([C8Py][Cl])) for this purpose. Measured IFT values between solutions of ILs and a southern Iranian crude oil reveal that these ILs are successful in reducing the IFT. Unlike traditional surfactants, these ILs are more effective as the salinity increases. Also the measurements revealed that there is a correlation of the IFT of the solutions with salinity and temperature.

Influence of Crude Oil Fractions on Interfacial Tensions of Alkylbenzene Sulfonate Solutions

The influences of crude oil fractions, such as acidic fractions, resins, and asphaltenes, on the interfacial tensions (IFTs) of kerosene against surfactant mixtures with different hydrophilic–lipophilic ability were studied by a spinning-drop interface tensiometer in the present work. The IFTs of crude oil, diluted crude oil, and treated crude oil by formation water against surfactant mixtures have also been investigated. The results show that a small quantity of acidic fractions will reduce the equivalent alkane carbon number (EACN) values of model oils and result in the slightly decrease of IFTs for surfactant solutions with higher water solubility. On the other hand, the superfluous addition of acidic fractions could obviously increase the IFT mainly because of the mixed adsorption of acidic fractions and surfactant molecules. The resin shows almost the same trend of effecting IFTs as acidic fractions because most acidic fractions with high surface activity distribute over resin fractions. However, the...

On the interfacial properties of micrometre–sized water droplets in crude oil

The remarkable stability of water–in–crude oil emulsions is due to the presence of a complex adsorbed layer at the surfaces of the dispersed droplets. Except for its role as a steric barrier, little is known about the in situ properties of this interfacial structure. In this study, new insights into the adsorbed layer are provided by direct micrometre–scale measurements. At low crude content in the bulk where, according to interfacial tension isotherms, there should be little or no surfactants on the droplet surface, the adsorbed layer displays pronounced rigidity and is capable of preventing coalescence and coagulation of the droplets. Such interfaces are highly dissipative and can be well described by the Boussinesq–Scriven model. As the supply of surface active materials in the bulk (i.e. the crude content) increases , the adsorbed layer transforms from a rigid structure to a fluid interface. This fluid layer continues to inhibit coalescence, although signs of weak interdroplet adhesion begin to appear. Under area compression, the fluid interface will discharge micrometre–sized emulsion droplets into the oil phase via a ‘budding’ mechanism.

Dewatering of crude oil emulsions 2. Interfacial properties of the asphaltic constituents of crude oil

The importance of the interfacial rheology in determining the stability of water-in-Buchan crude oil emulsions has been demonstrated in part 1 of this series of papers (R.A. Mohammed, A.I. Bailey, P.F. Luckham and S.E. Taylor, Colloids Surfaces A: Physicochem. Eng. Aspects, 80(1993)223). In part 2, interfacial tensions of crude oil, and solutions of asphaltenes and resins in a model oil have been investigated. Surface pressure vs. area (Π— A) curves of monolayers of asphaltenes, resins and their mixtures have been established. In its dependence on the ratio of resins to asphaltenes, the pseudostatic dilatational modulus has high values for low resin-to-asphaltene ratios and low values for high resin-to-asphaltene ratios. This is expected to throw light on the cause of the enhanced stability of water-in-crude oil emulsions.