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Despite numerous studies, there is a lack of fundamental understanding about the displacement behavior of surfactant-crude oil systems under the influence of different fractures' geometrical properties in five-spot systems. In this work, a series of flow visualization experiments were carried out on one-quarter five spot glass micromodels at various fractures' geometrical properties, such as fracture density and fracture continuity, under oil-wet condition. The influences of injection of Linear Alkyl Benzene Sulfonate and Sodium Dodecyl Sulfate surfactants as well as the effect of fracture geometrical parameters, on macroscopic and microscopic displacement behavior have been investigated. The micromodels were initially saturated with crude oil. Precise analyses of the high quality pictures, which were taken during experiments, were used to explore the surfactant's displacement efficiency. It has been found that two mechanisms govern such a process at the pore scale. One is responsible for decreasing the residual oil saturation and the other mechanism is increasing the matrix-fracture interactions through the porous media. The experimental results show that the magnitude of interfacial tension between the existing fluids was the most important parameter that altered the flow behavior at pore level. The observations revealed that high penetration of surfactant solutions from fractures into the matrixes perfectly postponed the breakthrough time and increased the oil recovery. As a result of better dispersion of surfactant through the matrix, it has been found that the higher fracture density yields a higher oil recovery. The media containing continuous fractures showed that higher oil recovery compared to discontinuous fractures. The results also showed that the average oil recovery during water injection is a strong function of the fracture properties, whereas use of Sodium Dodecyl Sulfate solution extremely reduces the effect of fracture geometrical properties. The results of this work can be helpful to better understanding the surfactant-crude oil displacements in fractured reservoirs. [ABSTRACT FROM PUBLISHER]

The injection of hydrocarbon gases/CO2for enhanced oil recovery can promote asphaltene precipitation and consequently reservoir impairment, of which its impact is tremendous. In this work, the results of flow dynamic tests performed on sandstone as well as carbonate rocks were presented. The permeability reduction mechanisms were investigated during simultaneously injection of CO2and recombined oil into core samples through a static mixer at reservoir conditions. The permeability impairment data was monitored from analysis of recorded pressure and online viscosity measurements during the experiments. Analysis of obtained results revealed that for both sandstone and carbonate rocks, surface deposition and pore plugging mechanisms participate simultaneously in reduction of permeability in primary injected pore volumes. Therefore, a new permeability reduction model is proposed that considers a combination of surface deposition and pore plugging mechanisms. The results of the new model are in good agreement with the obtained experimental data. The results of this work can be helpful for modeling of asphaltene deposition due to CO2injection in petroleum reservoirs. [ABSTRACT FROM PUBLISHER]

Surfactant flooding is known to lower the interfacial tension and, hence, reduces capillary forces responsible for trapping oil. Despite numerous experimental studies, little is known about the role of fracture geometrical properties on oil recovery efficiency during surfactant floods, especially in five-spot systems. In addition, application of sodium dodecyl sulfate for oil recovery in fractured media is not discussed well. In this study, two types of surfactant solutions have been injected into micromodels, which were initially saturated with crude oil, having different length, orientation, and distribution of fractures under oil-wet conditions. Precise analyses of continuously recorded pictures during the experiments were used to determine the oil recovery efficiency. The observations reveals that high penetration of surfactant solutions from fractures into the matrixes perfectly postponed the breakthrough time and increased the oil recovery by sweeping the oil in the matrix. This matrix-fracture interaction for the case of sodium dodecyl sulfate solution is much higher than linear alkyl banzene sulfonate floods. As a result of better dispersion of injected surfactant through the matrix, it has been found that the longer fracture yields a higher oil recovery. Fractures perpendicularly oriented to the pressure drop direction exhibit higher recovery than those oriented directly along the pressure drop path. As expected, the oil recovery of water flooding is highly dependent to fracture geometrical properties. Use of linear alkyl banzene sulfonate solution reduces the role of fracture geometrical properties, and this role is at minimum for the case of sodium dodecyl sulfate solution. Therefore, it can be concluded that the use of this surfactant can be a good candidate for decreasing the uncertainties of fractures' geometrical properties as an enhanced oil recovery method in fractured reservoirs. [ABSTRACT FROM PUBLISHER]