Surfactant systems for various fields of EOR: drilling fluids, microemulsions, control of viscosity, breaking of emulsions

Different areas for the use of surfactants in tertiary oil recovery and in oil industry will be discussed. The basic principles of the surfactants in these processes will be explained. In EOR the most important factors are the viscosity and the interfacial tension of the surfactant solution. The viscosity of the pushing fluid has to be matched to the viscosity of the reservoir oil and the interfacial tension of the oil/water interface should have a very low value of around 1.10-3 mN/m. It is shown that the viscosity of the fluid with about 1% surfactant can be adjusted between the viscosity of water and values of 100 Pas. However, the high viscosities break down when the fluids are in contact with oil and solubilize oil. Under these conditions always very low viscosities will be reached. It is therefore necessary to adjust the viscosity with water soluble polymers. Drilling fluids are another area where surfactants can be used. They usually contain surfactants, clays and water soluble polymers. It is demonstrated that in such formulations all components can interact with each other and these systems can form weak hydrogels with a strong shear-thinning behavior. While surfactants or amphiphilic compounds are used to prepare emulsions and stable dispersions, surfactants can also be used to break natural emulsions that are produced during the oil recovery process. Finally, it will be discussed that surfactant systems can be used for drag reduction during the transport of oil in pipelines or for the transport of waste water