Chemical flooding plays a key role in oil displacement to additionally recover more oil after the primary and secondary oil recovery have been exhausted. Surfactants are one of the most commonly and widely used in chemical enhanced oil recovery because of their capability to lower the oil-water interfacial tension; however, gravity seggregation and early breakthrough could be observed. These problems could be overcome by using foam flooding. Foam is generated by coinjection of surfactant solution and nitrogen gas as a mobility control in a porous media to help improve the sweep efficiency. In addition, blending of different structures of surfactants was employed not only to lower the oil-water interfacial tension from their synergistic effect but also to improve the foam properties. In this work, single and mixed surfactants systems between sodium dioctylsulfosuccinate (AOT) and internal olefin sulfonate (IOS) with three different carbon chain lengths were tested through phase behavior studies and interfacial tension measurements. The optimal type III middle phase microemulsion of each system was confirmed by its lowest interfacial tension and was chosen as the optimum formulation to study its performance in enhanced oil recovery. The results indicated that single surfactant system of both AOT and IOS cannot generate type III middle phase microemulsion. However, the mixed systems of 1:1 surfactant/cosurfactant ratio (AOT:IOS) generated the low interfacial tension middle phase microemulsion. Surfactant and foam floodings were conducted by a sand pack column at atmospheric pressure and ambient temperature. Although both surfactant and foam floodings gave comparable additional oil recovery, foam flooding gave earlier oil breakthough as compared to the surfactant flooding indicating the improvement in sweep efficiency of the foam flooding.

Optimal middle phase microemulsion in foam and surfactant flooding

256th National Meeting (2018)

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