Natural fractured reservoirs have a large contribution to the world’s hydrocarbon reserves. They have usually lower recovery, however a higher residual oil saturation. This is related to different wetting conditions in naturaly fractured reservoirs. Furthermore, natural fractured reservoirs have a lower matrix permeability compared to conventional reservoirs; the porosity for the fracture network is small. By utilizing of the chemical flood (Alkaline – Surfactant – Polymer flooding) in a reservoir with fractured network, it is possible to alter the wettability of the reservoir and decreasing the interfacial tension in the porous medium. Furthermore, it is possible to reduce the mobility ratio, which enhances oil recovery; by utilizing alkaline it is possible to form in-situ surfactants, which are able to reduce the amount of surfactants. Therefore, the residual hydrocarbon saturation will be reduced consequently. Due to the complex reservoir structure and description, chemical flooding operations underestimating the reservoir overall reservoir performance. Due to the natural fracture network, the modelling of chemical floodings will cause issues. It has to be noticed, that the storage occurs only in the pore volume of the matrix, however, the fractures have a significant contribution to the flow through the reservoir and the overall reservoir performance. This master thesis presents a comprehensive study on modeling ASP flooding in naturally fractured reservoirs and mainly addresses capillary forces, gravity, and viscous forces, fracture properties along with fractures using a dual porosity – dual permeability model. By looking into the mechanisms that are behind the oil recovery in different balances of forces, an insight will be given when and why tertiary recovery is working in reservoirs with a fracture network. To some extent, it addresses the effect of capillary and gravity number during the chemical flood acting in the naturally fractured reservoir and the possibility to relate the dimensional numbers with oil recovery rate by using a three-dimensional plot. Related to the benefits of Response Surface Methodology and extensive sensitivity analysis, a Tornado plot should give a broad insight, on how different varying reservoir and constraint parameters are affecting the oil recovery. In addition, the thesis addresses the performance of the oil recovery factor by diversifying fracture spacing, fracture, and matrix permeability as well.