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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. [ABSTRACT FROM AUTHOR]

Abstract Concerns about climate change have persuaded the researchers to examine CO 2 injection in the form of carbonated water (CW) into oil reservoir as a safe and effective CO 2 storage and enhanced oil recovery process. Although interfacial tension (IFT) between crude oil and injected fluid has a vital role on the displacement of fluids in porous media, the effect of CO 2 and crude oil type on the dynamic IFT of crude oil under different operational conditions is not well understood. Accordingly, this study was carried out to assess the effects of temperature, pressure, crude oil type and CO 2 on the dynamic IFT of crude oil/CW. To achieve this goal, two types of crude oil were provided from southern Iranian oil reservoirs and dynamic IFTs with CW were measured in a wide range of temperatures and pressures (i.e. temperature range of 30–80 °C and pressure range of 500–4000 psi); the obtained results were compared with the system without CO 2. In addition, the adsorption time of carbonated aqueous phase/crude oil, obtained based on the mono exponential decay model, was also compared with unadulterated water/crude oil system. The outcome of this study showed that crude oil type has the most significant effect on the IFT of crude oil/CW compared to pressure, temperature and CO 2 content. In more details, the IFT of crude oil/CW can be affected by the amount and type of acidic/basic components in the crude oil as well as pH of the aqueous solution. Besides, the obtained results revealed that the effect of temperature was more considerable on the IFT of the heavy crude oil compared with the light crude oil in both studied aqueous solutions (i.e. unadulterated water and CW). Although the inversion phase temperature was obtained for unadulterated water/studied crude oils at all studied pressures, this phenomenon was not observed for crude oil/CW at elevated pressure, due to the high amount of CO 2 at this condition. Highlights • Dynamic interfacial tension (IFT) of crude oil/carbonated water (CW) was studied. • Effects of temperature, pressure and crude oil type were examined. • Crude oil type showed the most significant effect on the IFT of crude oil/CW. • The effect of temperature on the heavy crude oil was higher than light crude oil. • Competition between CO 2 and ingenious surfactants ionization determined IFT trend. [ABSTRACT FROM AUTHOR]

The current investigation is aimed to investigate the effect of new families of ionic liquid (IL) based surfactants for considering the enhanced oil recovery process. Imidazolium based ILs with chloride anion ([Cn mim][Cl]) with long alkyl chains, (n = 12 and 18) are synthesized and their effectiveness on the interfacial tension (IFT) and emulsification phenomena at the co-presence of NaCl and Na 2 SO 4 salts are examined. Dynamic IFT and critical micelle concentration (CMC) values of different solutions were measured and determined. Moreover, the performance of the considered solutions at the CMC was examined on the wettability alteration of the oil-wet carbonate rock surface. The obtained results revealed that for the shorter alkyl chain length IL (C12), the presence of NaCl was more effective compared with the Na 2 SO 4 while a reverse trend is observed for the longer alkyl chain length IL (C18). The contact angle measurement revealed that IL solutions containing sulfate anion altered the wettability of the oil-wet surface (from about 160°) toward the strongly water-wet state (41° for C12 and 45° for C18) and alkyl chain length introduces no significant effect. Besides, the solution containing chloride anion affected by IL type, that means longer alkyl chain length (C18) was unable to change wettability toward the water-wet state and wettability changed to 113° while C12 changed wettability to 34°. It is also found that although increasing the concentration of both ILs led to the lower IFT values with the minimum value of 0.6 mN/m, raising the temperature from 298 K to 348 K increased the IFT values. • Wettability and IFT of long-chain imidazolium based ionic liquids (ILs)/crude oil are studied. • Performance of Cl− and SO 4 2− on the surface activity of ILs is investigated. • Alkyl chain length and temperature effects on IFT, relaxation time and micellization are also examined. • It is fond that the wettability, IFT and CMC point depends on salt type and IL alkyl chain length. [ABSTRACT FROM AUTHOR]