An Experimental Investigation of Surfactant Flooding as a Good Candidate for Enhancing Oil Recovery from Fractured Reservoirs Using One-Quarter Five Spot Micromodels: The Role of Fracture Geometrical Properties

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.