جستجوی مقالات مرتبط با کلیدواژه « کشش بین سطحی » در نشریات گروه « فنی و مهندسی »

The main advantages of surfactant flooding, including the reduction of the interfacial tension between the aqueous surfactant solution and the residual oil and wettability alteration, make it a very potential method for the enhanced oil recovery processes. Since the surface activity of surfactants and their critical micelle concentration (CMC) can be improved by mixing them, this study was aimed to evaluate the binary mixture of various surfactants, including cationic quaternary ammonium surfactant (CTAB), anionic surfactant (AOT) and non-ionic (Tween 80) with an imidazolium-based ionic liquid ([C12mim] [Cl]) in the volume ratio of 2:1. Binary surfactant mixtures have been investigated in low and high salt concentrations (650 ppm and 38350 ppm) to see the effect of salt concentration on each of the binary mixtures. After investigation of the interfacial tension of each of these mixtures, the phase behavior of each of them was investigated. In addition, the wettability alteration on dolomitic carbonate rock has been investigated. To simultaneously investigate the two mechanisms including interfacial tension reduction and wettability alteration, the spreading coefficient and capillary number were calculated. The results showed that despite the decrease in the interfacial tension of crude oil from 8.72 mN/m to less than 0.5 mN/m, this improvement has no significant impact on the creation of a favorable microemulsion and change the wettability alteration of dolomitic rock into strongly water wet state, as a result, no significant changes in the capillary number and spreading coefficient were obtained.

One of the most important methods of increasing extraction from carbonate reservoirs is to change the wettability of the reservoir rock with the emergence of nanotechnology, which played a significant role in the framework of methods of increasing Oil Recovery. The purpose of this project is to use nanofluids containing inorganic nanoparticles, which are economical and environmentally friendly. For this purpose, first, 3 types of inorganic nanoparticles SiO₂, Al₂O₃ and TiO₂, which were converted into nanometer size powder by mechanical method (Ball mill). Then, 3 nanofluids containing SiO₂, Al₂O₃ and TiO₂ were prepared along with dispersants and stabilizers. By performing the contact angle test, it was found that the contact angle of the oil drop on the oil-wet carbonate rock changed from 132.1° to 87.1° after coating with nanofluid with a concentration of at least 0.01 wt.%. Then the optimal concentration of nano fluid and the optimal time of thin section aging in nano fluid were determined, and the values of these parameters were 0.01% by weight and 7 days, respectively. In the following, it was shown that the stone coated with these nanofluids maintains its wettability well. Based on the interfacial tension test, it was shown that the interfacial tension decreased from 24.029 mN/m (water and oil) to 4 mN/m (nanofluid and oil) at ambient temperature. Finally, by conducting the Core Flooding test on the oil wet plugs, the investigations show that in the flooding test, the volume of extracted oil increased by 42.06% in the case of water injection to 60.09% in the case of nanofluid injection. (Residual oil decreased from 9.64 cm³ to 6.64 cm³ respectively.) In fact, the flooding recovery factor increased by 18% compared to the previous state.

Research Subject:

 In recent years, smart water flooding has gained attention regarding enhanced oil recovery, and one of its driving mechanisms is wettability alteration. However, the effect of acid presence on smart water performance needs to be clarified. Thus, the main question is whether the presence of acid and potential determining ions can lead to further wettability alteration and interfacial tension (IFT) reduction. Additionally, in this study, trivalent cations were added to smart water for the first time, and the results were compared with those of divalent cations. 

Research approach: 

In this study, seawater (SW), 4-times diluted SW, and 8-times diluted SW were prepared in distilled water, 0.001 normal HCl and 0.01 normal HCl, and the contact angle and IFT experiments were carried out. In addition, concentrations of Ca2+, Mg2+, and Fe3+ were adjusted in 8-times diluted SW prepared in 0.01 normal HCl, and the IFT and contact angle tests were conducted.

The results showed that the presence of acid in distilled water could decrease the IFT values; however, it did have a marginal effect on contact angle reduction. Also, because of synergistic effects between acid and potential determining ions, IFT significantly declined. While adding acid to brines with different salinities resulted in contact angle reduction, the glass surface remained oil-wet. Regarding divalent and trivalent cations, the results revealed that increasing Fe3+ concentration in smart water made the glass surface water-wet. However, adjusting Ca2+ and Mg2+ concentrations changed the wettability from oil-wet to neutral-wet. Moreover, divalent and trivalent cations showed similar behavior in IFT reduction, and a four-times increase in the concentration of each mentioned ion reduced IFT by about 2 mN/m.

Surfactant flooding is one of the most effective methods of the enhanced oil recovery (EOR) technique since it can reduce the interfacial tension (IFT) and wettability of the crude oil oil/rock/formation brine system. The aim of this study is to investigate the effect of ions (NaCl and Na2SO4) on the efficiency of two ionic liquids (ILs) namely 1-dodecyl-3-methyl imidazolium chloride ([C12mim][C])) and 1-octadecyl-3-methyl imidazolium chloride ([C18mim][Cl]) with different alkyl chain lengths on the IFT reduction and wettability alteration using works of adhesion and cohesion and spreading coefficient. Based on the critical micelle concentration (CMC) measurement, the efficiency of ILs at three different concentrations (C), C<CMC, C=CMC, and C=CMC, are investigated to evaluate the wettability alteration on the dolomitic carbonate rock surface and oil spreading coefficient. The results show that the performance of IL with longer chain length depends on the salt type, although the importance of surfactant concentration is dominant compared with salt type effect. To sum up, it seems that the IFT reduction can improve the performance of the solution for wettability alteration. The worth mentioning point is that the highest spreading coefficient is obtained for the IL with shorter chain length ([C12mim] [Cl]) in the presence of NaCl salt.

During recent years, Gemini ionic liquids (ILs), as a new type of surfactants, have gained much attention due to their significant interfacial activity. Accordingly, use of these materials to reduce crude oil-water interfacial tension (IFT) and to enhance oil recovery is much advantageous. In this study, effects of concentration, temperature and pH on the crude oil-water IFT in the presence of Gemini IL surfactants were investigated. For this aim, alkyl chain length imidazolium based gemini ILs of [C4im-C4-imC4][Br2] and [C8im-C4-imC8][Br2] were synthesized and used. By measuring IFT of the system, under different conditions, the corresponding variations were considered. Results revealed the strong effect of alkyl chain length and concentration on the IFT, leading to, respectively, 72.5 and 97.5% reductions under critical micelle concentrations and temperature of 298.2 K. The Gemini IL surfactants were stable at high temperatures and under a wide range of pH, and that their performance was significantly promoted with these factors. In theoretical investigation, it was revealed that the experimental data were nicely consistent with the Frumkin adsorption isotherm and the obtained parameters with reasonable variations.

Due to the complex nature of carbonate reservoirs, mechanisms behind low salinity water injection (LSWI) in these reservoirs are not well understood compared to sandstone ones. Using a limestone core and crude oil from one of the wells of the Shadegan oil field, a core injection test was performed with a sequence of high salinity-low salinity water. 10-time diluted seawater, as low salinity water, was able to recover 14.5% of initial oil in place (IOIP) following the secondary injection of seawater. In contrast, the tertiary injection of the low salinity bine into artificial pure calcite rock (with petrophysical properties similar to real rock) recovered only 3.4% of IOIP. Using the results of the contact angle test, the improved oil recovery by LSWI is attributed to wettability alteration towards a more water-wet state. However, the amount of wettability alteration in Shadegan oil field limestone (42°) is significantly higher than that of pure calcite rock (16°). Based on the results of zeta potential, the wettability alteration by low salinity water is attributed to the more negative electric charge of the crude oil/brine and rock/brine interfaces. The increasing trend of pH with decreasing the salinity showed that more CO32- adsorption at low salinity reduces the electric charge on the calcite surface. The electric charge of Shadegan oil field limestone, by reducing the salinity of injected water from seawater to 10-time diluted seawater, experienced a greater decrease (7.7 mV) than pure calcite (4.1 mV). XRF results attributed this behaviour to the presence of impurities such as silica, sulphate, and phosphate in the Shadegan oil field limestone.

Research subject: 

In water injection process, part of the surface active agents that are naturally present in oil can be dissolved in injected water. The presence of these substances affects the surface phenomena of the three phase water-oil-rock system. The effect of these substances on modification of the ionic composition of injected water has been less investigated in previous studies.

Research approach:

 In this paper, first, the effects of acidic compounds in crude oil and connate water composition on initial wettability of carbonate rock were investigated. Then to investigate the wettability changes of oil-wet calcite rock, single-salt aqueous solutions of MgCl2, CaCl2, KCl, and Na2SO4 having concentrations of 0.1 to 1 molar were used.Oil–water interfacial tension (IFT) for distilled water and salt waters in various concentrations were measured and compared. Variations of calcite rock surface properties were investigated by contact angle measurement after aging of thin sections in oil and salt waters.

Results indicated that by increasing ion concentration and ionic strength of salt waters, IFT decreases due to dissolution of acidic compounds of oil at the interface of oil and water. Moreover, for high content of acidic compounds in the oil, Magnesium ion has the most impact on reducing IFT and altering the rock wettability. So that by increasing the concentration up to 1 molar, IFT and contact angle decrease to 1 mN/m and 42 degrees, respectively.Contact angle measurements revealed that the composition of connate water is effective in changing the initial wettability of the rock, and formation of ionic-organic layer adjacent to the rock surface is one of the most important factors in wettability alteration. The presence of Magnesium ion in connate water decreases the contact angle to 145 degrees and causes the rock surface to become more water wet.Also, increasing solubility of oil-soluble acidic compounds in the aqueous phase has a significant effect on the rock wettability. The experimental results showed that the interaction between ions in the aqueous phase, especially the divalent ions, and surface active agents (carboxylic acid) determine the surface behavior of water in contact with oil and rock.

The gas mobility control is one of the main challenges during gas injection. It causes early gas break through and decreases the sweep efficiency due to low viscosity. In this study, the small molecule thickener (P-1-D, MW=910 g/mol) was used to improve the CO2 mobility control at reservoir conditions. The small molecule thickener can dissolved in gas without any co-solvent. It leads to the small molecule thickeners which may be used to the EOR field application in comparison with high molecular thickeners. The cloud point pressures were calculated to ensure that the single phase condition has occurred between CO2 and gas thickener. In addition, the effect of gas thickener on CO2 viscosity was investigated for 5000, 10000, 30000, 50000, 80000, and 100000 ppm P-1-D concentrations. Moreover, the impact of P-1-D thickener on interfacial tension (IFT) was studied. The results illustrated that the cloud point pressure for gas and CO2 thickener decreased by increasing in P-1-D concentrations and all of these are below the reservoir pressure. Also, the gas thickener increased the CO2 viscosity 15.7 fold for 80000 ppm concentration which can improve the gas mobility control. Finally, the IFT decreased in presence of the gas thickener which can provide the miscibility condition for at least 10000 ppm concentration.

In this study, the effect of water-soluble amphiphilic compounds of crude oil and ionic composition of water, on surface and interfacial tension were investigated. Distilled water and salt water of NaCl and Na2SO4 in five ionic strengths up to 2 molar were contacted to the crude oil to be saturated with crude oil amphiphilic compounds. The effect of these compounds on water properties are examined with pH, total organic carbon (TOC), surface tension and interfacial tension tests. Finally, the obtained results show that a low amount of acidic and basic compounds of crude oil were dissolved in contacted waters which have significant effect on surface and interfacial tension. In addition, the results reveal that by increasing the ionic strength of NaCl and Na2SO4 salt water, there is optimal salinity between 0.1 and 0.25 molar.

One of the most important challenging subjects for scientists is the numerical simulation of the transport phenomena in heterogeneous media. The discontinuity in the properties causes computational errors leading to incorrect estimation of the exact values. Various methods were rendered to reduce the error. Most of these methods are based on the remeshing of the elements to align with discontinuities increasing the calculation cost significantly. One of the powerful methods introduced recently is extended finite element method (XFEM). XFEM is based on the modification of the interpolation functions to capture discontinuities throughout the domain. Using this method in fluid mechanic was merely addressed but recently the approach has been changed. So, in the present study, attempts were made to study the affecting factors on the deformation of Newtonian/Newtonian and non-Newtonian/Newtonian systems. The obtained results showed a good agreement with the experimental results by other scientists. Because of pressure field modification, studying droplet deformation becomes possible, even when rheological properties of component like viscosity ratio and interfacial tension are very different. The obtained results indicated that by fixing all rheological parameters, there will be an inverse relationship between the final droplet size and viscosity ratio of components.

The enhancement of energy consumption and increasing demand for oil have led to using improve oil recovery methods. Chemical enhanced oil recovery methods are among the most widly used techniques. Generally, the effect of these methods has been less than the predicted amounts by the studies. One of the leading causes, could be due to the loss of chemicals by adsorption or precipitation of the surfactants on the rock surface. The mineralogy of the reservoir rocks is effective in determination of the interaction between the bulk of the fluid phase and rock surface. This effect will change in the surface charge of the adsorbent and wettability alteration of the rocks.

In this study, the adsorption of AOT surfactant on the surface of a hydrophilic adsorbent of carbonate reservoir was investigated. For this purpose, after the preparation of rock and fluid samples, the adsorption of surfactant was investigated in concentrations below and above the CMC.

Batch adsorption experiments were conducted to measure the amount of surfactant adsorption on the surface of carbonate rock. First different concenteration of AOT solutions and carbonate rock as adsorbent were combined. After 48h, the equilibrium concentrations were determined by using the calibration curve and. The amount of surfactant adsorption can be calculated by knowing the maqnitudes of equilibrium and initial concentration of the surfactant.

The results showed that by increasing the concentration of the surfactant in the liquid phase, the adsorption increased until it reaches a saturation point at the concentration of 1200 ppm. The results of the modeling showed that the Freundlich equilibrium isotherm with 1⁄n equals 0.8971 was the best fit for describing the prediction of AOT surfactant adsorption behaviour.

The application of polymers is one of the key techniques in different improved oil recovery (IOR) methods, namely polymer flooding, surfactant-polymer flooding, and alkaline-surfactant-polymer (ASP) flooding. Contact between polymers and surfactants in the reservoir, however, may cause some interactions between the two materials, leading to undesirable changes in their performance. In addition, flooding with polymeric surfactants is an attractive solution to this problem. Moreover, polymeric surfactants, in which hydrophobic groups are attached to hydrophilic polymers, simultaneously exhibit some properties of polymers and surfactants such as increasing the viscosity of solution, reducing the interfacial tension between water and oil, and also changing the wettability of the reservoir rock. In this study, polyacrylamide is hydrolyzed and using a zwitterion hydrophobic group, a new zwitterionic polymeric surfactant is synthesized. FTIR and HNMR identification tests verified the success of the process. The impact of hydrolyzed polyacrylamide (HPAM) and zwitterionic polymeric surfactant on water-oil interfacial tension, fluid viscosity, and shear rate were measured in the presence of CaCl2, MgCl2, K2SO4, and NaCl. Our results show that while HPAM reduced the interfacial tension to 13.65 mN/m, hydrophobically modified zwitterionic polyacrylamide (HMZPAM) reduced interfacial tension to 4.41 mN/m. While in similar conditions Hydrolyzed polyacrylamide reduces the interfacial tension to 13.65 mN/m. In salinity of 10,000 Mg/L, the viscosity of HPAM and HMZPAM were measured as 62 cP and 174 cP respectively. HMZPAM also showed better properties in elevated salt concentrations and shear rates. Finally, at the shear rate of 400 S-1, the apparent viscosity of HPAM and HMZPAM were equal to 0.14 cP and 1.06 cP respectively.

is one of the most common improved oil recovery method in the world. High residual oil saturation at the end of this method is due to low macroscopic sweep efficiency and viscous fingering. It can be improved by the mobility control during polymer solution injection. In this study, by of silica/ the effect of it on IFT, viscosity, and was investigated. In addition, the performance of in high salinity water was studied by using nano particles. The zeta potential results show that the stability of polymer solution was enhanced in of nano particles in high salinity water condition. Also, the lowest IFT was obtained for contained 1 percent nano silica (18.34 ), and the most tendency to water wet conditions was provided for this concentration. In addition to, 1 percent nano silica/ has the best performance on formation water viscosity and improved the mobility ratio to 1.07, which it can increase the oil recovery.

Microfluidic chips in the last two decades have had significant advances in the analysis of interfacial tension phenomenon due to their many advantages. To analyze interfacial tension phenomena, droplet flow in microchannels can be used. In this study, water-n-hexane interfacial tension in the presence of surface-active agents was measured, using microfluidic tensiometry. For this purpose, a glass microfluidic flow-focusing junction was fabricated for generating n-hexane droplets within an aqueous phase. The dependence of droplet size on the concentration of surfactants has been investigated. A theoretical equation was developed, considering force balance on the droplet generation in the microfluidic device, giving a relation between the interfacial tension and the generated droplet sizes. By standardizing the microfluidic chips with the aid of a system, whose interfacial tension is known (hexane normal and tween 20 in distilled water), interfacial tension can be measured with measuring the size of produced droplets for other systems that can form droplets in the microchannel. In this study, the microfluidic device and the relation were employed to measure the interfacial tension in the presence of either of sodium dodecyl sulphate (SDS) or Cetyl trimethylammonium bromide (CTAB) surfactants. It was found that the measured interfacial tensions deviate less than 10% compared to those measured with a commercially available ring method.

Surface active agents (surfactants) as the most important chemicals to enhance oil recovery (EOR) can reduce interfacial tension between the injected aqueous solution and the oil in a reservoir. They change wettability of the porous media to release and move the remaining oil trapped in the pores and throats towards the well. According to the important roles of the surfactants, it is necessary to predict their performance for EOR process. In this research, two data-based mathematical models were developed to estimate interfacial tension of the oil, salty water and anionic surfactant system using 598 experimental data. To obtain the correlations between the independent variables and the objective function, genetic programing has been applied. Squared correlation coefficient (R2) of the models is 0.946 and 0.9387; moreover, root-mean-square deviation (RMSD) of the models is 3.4439 mN/m and 3.3261 mN/m respectively. Simplicity and acceptable estimation are particular features of the models.

In recent years, with the advancement of nanoscience, many scientists have used nano materials to solve existing problems in various sectors of oil industry. Nanofluids made with these materials can facilitate the separation of oil and gas in a reservoir and increase oil recovery factor compared to current methods. Therefore, in this work, the effect of clay nanoparticles on oil recovery factor was investigated. For this purpose, two different base fluids, water and ethanol, were used to disperse the nanoparticles. The effect of adding clay nanoparticles on viscosity changes and interfacial surface tension was determined. Also, in order to investigate the effect of nanoparticle concentration in the base fluid on the ultimate oil recovery factor, nanofluids with 3 and 5 wt% were prepared. Results show that oil recovery factor increases significantly in these conditions by adding them into the base fluid, though nanofluids included clay nanoparticles have less stability. Also, the effect of these nanoparticles dispersed in water is greater than in ethanol. For example, at 5 wt%, oil recovery factor for water based nanofluid was 49.7% and for ethanol based nanofluid was 46%.

Ultrasound assisted oxidative desulfurization (UAOD) is a new process for the sulfur removal from different middle distillate cuts. In the UAOD process, at first, the sulfur-containing compounds are oxidized using a suitable oxidation system under ultrasound irradiation. Then, the oxidized sulfur-containing compounds are separated by solvent extraction. In the present study, the effect of interfacial tension between aqueous and hydrocarbon phases on the sulfur removal of diesel fuel has been investigated for the first time. The selected oxidation system was hydrogen peroxide/formic acid system. In this regards, three different surfactants including anionic, cationic, and nonionic surfactants have been evaluated. The results revealed that the application of sodium dodecyl sulfate (SDS) as an anionic surfactant and cetyltrimethylammonium bromide (CTAB) as a cationic surfactant leads to the sulfur removal of 82.65 and 83.10% after oxidation followed by solvent extraction respectively. The sulfur removal in the absence of surfactants was 81.61% in the same oxidation and extraction conditions. The application of span 60 as a nonionic surfactant leads to a decrease in sulfur removal to 78.65% in the same oxidation and extraction conditions. However, the application of span 60 leads to about 3% increase in the sulfur removal in comparison with the case without surfactant after the oxidation step. Therefore, the addition of surfactants can lead to a positive effect on the oxidation step due to decreasing the interfacial tension between aqueous and hydrocarbon phases and a negative effect on the extraction step of the UAOD process.

Multi-phase fluid flow through porous media is strongly dependent on interfacial tension of immiscible fluids. Fluid mechanics will be affected by changing the interfacial tension. This paper describes a new approach to predict the interfacial tension at the oil-water system in the presence of an ionic surfactant. This study equation is based on Butler equation, often used for obtaining surface tension equations at different interfaces. The Debye–Hückel theory is used to determine activity coefficients of surfactant in the bulk phase. Cationic surfactants, including decyl trimethylammonium bromide (C10TAB) and dodecyl trimethylammonium bromide (C12TAB), are used to validate the equation. The new final equation can properly describe the alkane-water interfacial tension in the presence of single surfactant solutions. In this study, alkanes, including hexane, heptane, octane, decane, dodecane, and tetradecane are considered as the oil phase. The following parameters are obtained by curve-fitting: 1- molar surface area, and 2- bulk-surface distribution coefficient of surfactant. The alteration of equation parameters at different alkane-water systems is discussed. The newly developed equation is in a good agreement with the literature experimental data. This approach can be particularly important in the practical use of surfactants for the reduction of oil-water interfacial tension when experimental data are rare.

The impact of Co3O4 nanoparticles with concentration of 0.1 wt%has experimentally been studied on (1) interfacial tension, (2) asphaltene precipitation and (3) miscibility with the carbon dioxide, when the Co3O4 nanoparticles have been added to one of Iranian crude oils and synthetic oil solutions . To do so, the Vanishing Interfacial Tension (VIT) technique has been used for a pressure of up to 1200 psi. The results have been showed that in the presence of Co3O4 nanoparticles, IFT, Minimum Miscibility Pressure (MMP) and severity of asphaltene precipitation have all been reduced to some extent. Within the range of operating conditions attempted here, MMP has reduced as much as 32% and 19% for the synthetic and crude oils, respectively. The severity of asphaltene precipitation has also reduced approximately 13% for the asphaltenic synthetic oil and 7% for the investigated crude oil. The experimental results appear to show that Co3O4 nanoparticles served to adsorb asphaltene which would, in turn, facilitated the solubility of CO2 in synthetic and crude oils which consequently would lead to enhanced oil recovery.

One of the major problems in Enhanced Oil Recovery (EOR) processes is the precipitation and deposition of asphaltene. This may lead to formation damage or partial and utter obstruction of flow passages around the well, deposition of asphaltene on the surface of reservoir rock as well as wettability alteration from water- to oil-wetted, and deposition in processing units. The present study investigates the miscibility of synthetic oils with or without asphaltene and compares it with that of crude oil from one of the Iranian oil fields in the presence of CO2 gas using vanishing interfacial tension (VIT) technique. The experiments were conducted at a given temperature but for different pressures. The experimental results showed that normal paraffin, in the oil phase, served as instability agent for the precipitation of asphaltene. The higher content of n-paraffin resulted in more and faster precipitation of asphaltene at the gas/oil interface. Once this occurred then the slope of IFT curve between gas and oil increased resulting in decreased CO2 solubility. Furthermore, based on IFT measurements, the speed of approaching to miscibility is reduced in vicinity of the onset of asphaltene precipitation. Thus, asphaltene aggregation in the gas/oil interface is accompanied by reduced slop of VIT curve which made the miscibility condition harder to reach.