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Carbonated brine (CB) injection, known as one of the effective enhanced oil recovery processes, is highly dependent on the reservoir conditions (i.e. temperature and pressure) as well as the type of dissolved salt in aqueous solution. This study is aimed to investigate the influential parameters on the swelling of crude oil as the most important mechanism during CB injection. The swelling of crude oil in the presence of different CB solutions consisted of different salts such as KCl, NaCl, CaCl2 and MgCl2 with constant concentration of 15,000 ppm is studied using a high-pressure, high-temperature visual cell which measures the volume of drop using image processing software based on Young-Laplace method. Also, the Δ Bond number of crude oil is examined to more reliably find out the mechanisms. According to the results, it can be concluded that the solubility of CO2 in aqueous phase is not the only parameter affecting the swelling behavior, and that the crude oil and ion type as well as temperature have remarkable effect on the mobility of CO2 molecules and their partitioning from aqueous phase toward oil phase.

In the current study, a novel approach which takes into account the effectiveness of both convectional surfactants and biosurfactants was investigated. The biosurfactant produced by Enterobacter cloacae strain was utilized concomitant with conventional surfactant (sodium dodecyl benzene sulfonate (SDBS)) to evaluate its capability to reduce the SDBS adsorption on rock surface (biosurfactant acts as sacrificial agent) or synergistically enhance the effectiveness of the SDBS. In this regard, the wettability alteration and interfacial tension (IFT) measurements and calculation of spreading coefficient were performed considering two different scenarios. In the first scenario, SDBS was added to the incubated bacterial solution medium while in the second case, SDBS was added to the bacterial solution before the incubation stage. Based on the obtained results, it was revealed that the wettability altered from original oil wet towards water wet state using bacterial solution, while the addition of SDBS deteriorated this trend for both scenarios. According to IFT measurements, the first scenario was more effective than the individual solution of bacteria and SDBS as well as the second scenario. In conclusion, the measured spreading coefficient demonstrated that the bacterial solution was a more effective EOR agent in comparison to other studied cases.

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 Na2SO4 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 Na2SO4 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.

The impacts of salinity adjustment of displacing fluid have recently gained special attention to enhanced oil recovery (EOR). Different mechanisms have been studied widely in the literature while some of them are still subjugated to more scrutiny. The effects of diluted sea water on the interfacial properties of brine and asphaltenic-acidic crude oil and the wettability alteration of carbonate reservoir rock are investigated in this experimental observational work. The measurements of interfacial tension (IFT) and contact angle (CA) as two main parameters are studied. Besides, the effects of asphaltene and resin in the crude oil on the IFT values between the crude oil and aqueous solution are investigated. The experimental results show that the lowest IFT values are obtained at high salinity conditions, while the surface rock wettability alterations are observed at low salinity conditions. Based on the obtained results, a combined mechanism is proposed to describe the wettability alteration towards more water wet at low salt conditions.

It is generally believed that asphaltenes and resins as the polar components in crude oil can get adsorbed at the oil/water interface and act as a surface active agents. However, due to the complex behavior of asphaltenes and resins, the understanding of their surface properties is challenging. In this work, the effects of addition of six electrolytes: NaCl, KCl, Na2SO4, MgSO4, MgCl2, and CaCl2 have been employed to experimentally evaluate their effect on dynamic interfacial tension of asphaltenic and resinous in oil/water interface. All of the electrolytes had the same ionic strength (0.7 M) and the pedant drop shape method was used for analysis. For this purpose, asphaltene and resin fractions of a crude oil sample with 27 API° are extracted and analyzed with elemental and Fourier-transform infrared spectroscopy (FTIR) analyses. Then, two synthetic oils samples prepared based on dissolution of extracted asphaltene and resin in toluene, their dynamic interfacial tension (IFT) values are measured in the presence of different brines. The adsorption/relaxation reorganization times of asphaltene and resin components at the oil samples/aqueous solution interface are evaluated with exponential decay model. Results suggest that divalent cations, Ca2+ and Mg2+, possess higher affinity toward the polar groups of asphaltene and resin components in the presence of Cl− compared to SO42−. Specially, Ca2+ is more preferred over Mg2+, particularly for resinous oil sample. Due to the higher affinity of the polar functional groups toward the interface in the presence of CaCl2, the lowest adsorption time was obtained for CaCl2, which refers to the time required for coverage and packing of active agents at the interface.