An experimental study on using a nanosurfactant in an EOR process of heavy oil in a fractured micromodel

Surfactant flooding is known as a common chemical method for enhancing oil recovery. Recently, the simultaneous application of nanoparticles and chemical substance has been considered for improving the efficiency of EOR processes. Nanoparticles along with surfactants, due to decreasing interfacial tension (IFT) between oil and water, the spontaneous formation of emulsion, the alteration of porous media wettability, and the modification of flow characters, lead to improving oil recovery and releasing residual oils remained inside pores. In the present study, the microscopic and macroscopic efficiency of heavy oil recovery in a fractured 5-spot model in three cases of injecting, two types of surfactants (SDS as an anionic surfactant) and (C12TAB as a cationic surfactant), injecting ZrO2 nanoparticles, and simultaneously injecting the nanoparticles and the surfactants was investigated. Adding the nanopartides along with SDS (2000 ppm) decreased IFT by 81%, while the figure for C12TAB was about 70%. Obviously, SDS surfactant showed better performance than C12TAB in terms of reducing IFT. This means SDS has a greater impact on decreasing IFT than C12TAB when used either alone or with nanoparticles. Moreover, the results of sessile drop experiments and wettability measurements showed that coating with heavy oil, could make an oil-wet surface. While coating with either the surfactants or the nanoparticles could partially alter the wettability of surface to water-wet, coating with the surfactants along with the nanoparticles could make a strongly water-wet surface. Seemingly, during the flooding tests, the distribution of surfactants containing nanoparticles in pores and throats showed a strong water-wet condition in microscopic pictures. In this regard. C12TAB showed better performance in terms of altering wettability than SDS. This means C12TAB has a greater impact on altering wettability than SDS when used either alone or with nanoparticles. However, the results of flooding tests showed that adding nanoparticles to surfactants solutions significantly increased oil recovery. In general, the cationic surfactant (C12TAB) solution containing nanoparticles enhanced ultimate oil recovery further than the anionic surfactant (SDS) solution containing nanoparticles. However, the experimental results showed that the minimum IFT was achieved using SDS either with or without nanoparticles, while C12TAB/nanoparticles mostly altered the wettability toward a water-wet condition. In addition, adding the nanoparticles to the surfactant solution lead to the modification of the flow character from Newtonian to non-Newtonian (pseudoplastic) and a consequent viscosity increase by 2 times. This can be assumed a great achievement as a nanosurfactant solution, in addition to its own duty, can be used to control mobility ratio in EOR processes. Obviously, an appropriate mobility ratio greatly affects the macroscopic oil recovery efficiency. (C) 2014 Elsevier B.V. All rights reserved.