In this study, six core samples were obtained from the Middle Bakken Formation in North Dakota. Before the imbibition experiment, petrophysical analysis were conducted for the samples. XRD method was used to analyze the mineral composition. Nitrogen adsorption and SEM methods were combined to study the pore size distribution and microstructures. Then the authors performed brine imbibition and surfactant imbibition for six Bakken cores and two Berea sandstones. Before the experiment, the cores were fully filled with Bakken crude oil. The core plugs were then submerged into the brine and surfactant solutions with all-face-open (AFO) condition. Experiments of brine and surfactant imbibing into oil-filled cores were carried out with recording of recovered oil volume using imbibition cells. Different types of surfactants such as cationic, anionic, and nonionic, were tested in the study. Those experiments evaluate the oil displacement efficiencies of brine and different surfactants in Bakken rocks.

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