Chemical EOR processes had gained popularity in recent years as a result of breakthroughs in chemical formulations and injection procedures. Polymer injection (P) is a technique for enhancing oil production in secondary and tertiary floods by boosting sweep and displacement efficiency. There had recently been a lot of interest in chemical flooding for a variety of problematic scenarios. Reservoirs with high temperatures, formations with severe salinity and hardness, naturally cracked carbonates, and sandstone reservoirs with heavyweight and viscous crude oil are among the challenges. The first section of this paper reviews recent principles of polymer flooding, including mechanisms of polymer solution. Polymer types used in (EOR), rheology of polymer solutions in porous media, polymer degradation, polymer flooding experiments, and wettability measurement. The second section is about polymer simulation.