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Although the terms Low Salinity Sea Water and Smart Sea Water have been used interchangeably as one of Enhanced Oil Recovery methods in recent years, the present study shows that there are some differences between these two. To prove the claim, the role of salinity and aging time on interfacial tension reduction and contact angle alteration of a crude oil/brine/rock system is investigated using both smart sea water and low salinity sea water. Moreover, the governing mechanisms of the IFT variation and wettability alteration are discussed. For this purpose, the seawater solution is diluted with distilled water and at the optimal salinity NaCl, CaCl 2 , and Na 2 SO 4 salts are added to the solution. Next, the IFT of brine and oil, and the CA of the oil drop are measured on the carbonate surface in the presence of brine. The results showed that IFT between low salinity sea water and oil was decreased with increasing salinity and then increased. In this regard, similar results were observed by adding NaCl, CaCl 2 , and Na 2 SO 4 to a low salinity seawater (LSSW) solution. Additionally, reducing seawater salinity improved the wettability from oil-wet to neutral wet such that the optimum wettability range was achieved by adding Na 2 SO 4 to the LSSW solution. The effect of aging time in the low salinity sea water solution and smart sea water resulted in a reduction in the interfacial tension and the contact angle, as well as improving the crude oil/brine/rock interface. The mechanisms governing the reduction of the interfacial tension of low salinity sea water and smart sea water were surface excess concentration, salting in effect, and boiling point reduction, while the dominant mechanism for changing the wettability of low salinity water and smart sea water were the pH rise, pseudo-alkaline behavior, double layer increase, carbonate surface dissolution and salting in effect. • Major mechanisms are introduced to describe the crude oil-brine-rock interactions in smart sea water flooding and low salinity seawater. • Smart sea water flooding causes a significant change in wettability from oil wet to the desirable range of wettability. • Aging time can play an important positive role in successfulness of the smart sea water and low salinity sea water process. • IFT variation and its hidden mechanisms are investigated. • Compare between low salinity sea water and smart sea water effect on carbonate rock surface. [ABSTRACT FROM AUTHOR]

Nanoparticles (NPs) have been recognized as the agents that can improve the oil recovery given their positive impact on the surface wettability of rocks. However, their impacts on the interfacial tension (IFT) of the two-phase fluid in a reservoir have not been widely reported. Given the significant impact of IFT on the oil recovery, it is important to develop an NPs based approach that not only alter the surface wettability but also reduce the IFT. This may be accomplished by combining nanofluids with low salinity water (LSW). In the present study, LSW and NPs are combined to study their impacts on the IFT of a two-phase flow system with water and oil. IFTs of different solutions with nano glass flakes (NGFs) and nano silica (Ns) were measured in the presence of monovalent and divalent salt ions. The results obtained were analysed using two different models as a function of time. It was found that NGFs and Ns have similar efficiency in reducing the IFT and can reveal an optimum performance once their concentration reaches 24.8% in the solution. It was observed that, unlike Ns, IFT can be further reduced by LWS in the presence of NGFs. In fact, reduction of salinity up to 3500 ppm can decrease the IFT in the NGFs solution by the salting-in effect or migration of oil components. Changing the pH of the system can also reduce the IFT, but fluctuations was observed once pH goes beyond 9. It appeared that the tension in the interface between water and oil reduces over time and the effect of adsorption time is significantly higher on the solutions with nanoparticles. It was concluded that combining NGFs with LSW not only reduces the concentration of NPs needed and can make the project economically feasible, but also favourably change the IFT during the flooding process. The findings of this study may help to understand how LSW, and nanofluids can be employed together for a better oil recovery. [Display omitted] • Nano fluid can be combined with Low salinity water for a better EOR. • Combination of low salinity water and Nano glass flakes causes a significant change in the interfacial tension (IFT). • Nano glass flakes would have a better impact on the IFT compared to nano silica. [ABSTRACT FROM AUTHOR]

In recent years, natural surfactants have been considered as part of the EOR processes given their non-toxic and environment friendly nature. However, once chosen wisely, surfactants can only reduce the interfacial tension (IFT) and are often unable to alter the surface wettability for a better hydrocarbon production. Low salinity water (LSW) is a good candidate on these occasions, but the interaction of LSW with natural surfactants for wettability alteration has not been deeply understood. In this work, an attempt was made to extract and characterize a natural surfactant which could be used together with LSW for EOR purposes. To do this, a natural surfactant was extracted from Saponin and its physico-chemical properties such as CMC, foamability, and thermal stability were tested. A series of IFT and wettability measurements were then conducted to evaluate the performance of the surfactant as an EOR additive. The results obtained indicated that the extracted surfactant has a high thermal stability and can be fully functional in the temperature of up to 100 °C. It appears that increasing the level of salinity in the solution can improve the efficiency and foamability of the surfactant. It was observed that the extracted surfactant as can reduce the IFT of an air-water system by 78.65% and is capable of favorably altering the surface wettability of sandstone for a better hydrocarbon production once combined with LSW. • LSW with natural surfactant can improve the oil/water interface. • Natural surfactant has a high thermal stability and foamability. • Combination of Natural surfactant and Low salinity water can favorably change the foam height. • Natural surfactant has the good performance in crude oil/water/rock interface at LSW. [ABSTRACT FROM AUTHOR]

Rock typing is a process through which reservoir layers are classified into distinct units with similar geological conditions. The Kozeny-Carman's equation is commonly used for rock typing based on the porosity-permeability relationship, but it only considers spherical grains in its calculations which does not give representative results on many occasions. Thus, an attempt was made in this study to develop a new mathematical equation to correct the porosity-permeability relationship in rocks with ellipsoidal grains. To validate this equation, several pore-scale models were analysed using the Discrete Element Method (DEM) where the porosity was calculated under different conditions. The permeability of the pore scale models containing ellipsoidal (spheroidal) grains with different aspect ratios were then determined using the Lattice Boltzmann Method (LBM). This was followed by applying the new equation by incorporating the eccentricity of grains in the correction shape factor of the Kozeny- Carmen's equation. The results obtained indicated that any deviations in the sphericity of the grains (increase or decrease in the aspect ratio) increase the permeability of the model. In other words, the developed pore scale model with the aspect ratio of 1.0 (spherical grains) had the lowest permeability at the same porosity. This could be due to the bridging of pores with the ellipsoidal grains which causes a longer and narrower fluid path. Moreover, the models with the aspect ratio of 0.5 and 2.0 had a similar porosity-permeability correlation which could be linked to their similar packing structure. The new equation was further validated through the literature and numerical studies to ensure its accuracy under different geological conditions. • The equation through incorporating eccentricity of grains in the correction shape factor of the Kozeny-Carmen's equation. • The correction factors can highlight the relationship between the porosity and permeability in ellipsoidal grain shapes. • The elliptical grains tend to arrange themselves horizontally which positioned their longer axis aligns. [ABSTRACT FROM AUTHOR]

Undesirable water production due to water coning in hydrocarbon reservoirs has been a long-standing issue. This phenomenon decreases the oil production rate, increases the water cut and ultimately leads to early well-shutdown. Water coning may also interrupt the well testing data acquisition used to determine the reservoir permeability. In this study, attempts are made to propose a new approach which can control the water coning and estimate the reservoir permeability simultaneously. This was done by proposing a new boundary control model that was coupled by the Ensemble Kalman Filter (EnKF). A synthetic case study was considered to evaluate the performance of the EnKF associated boundary control (EnKF-ABC) approach. The results obtained indicated that the water cone development is controlled by the proposed method. In addition, the proposed method was also successful to estimate the reservoir permeability in the presence of water cone with less than 20% error after 12 times of downhole data acquisition. Even in the worst case scenario where there was a significant uncertainty in the initial estimated permeability, all the permeability ensemble members converged after about 200 days and tended to the real permeability after 500 days with less than 5% error. It was also observed that the Root Mean Squared Error (RMSE) of permeability sharply decreases when the ensemble size exceeds 15. The proposed approach is robust and reliable even where the mean of initial estimated permeability is considered quite far from the actual one. The EnKF-ABC approach proposed in this study can be applied to those production wells that suffer from water coning and there is lack of prior knowledge about the reservoir permeability. • Control the water coning by new approach. • Estimate the reservoir permeability simultaneously in presence of water coning. • A new boundary control model couple with Ensemble Kalman Filter (EnKF). [ABSTRACT FROM AUTHOR]