Polyacrylamide (PAM) is a commonly used chemical in tertiary oil recovery due to its ability to increase the viscosity of injected water and improve sweep efficiency. In this process, PAM is mixed with water to form a thick solution that is injected into the reservoir after primary and secondary recovery methods have been used. The PAM solution helps to displace trapped oil by reducing the mobility of the injected water and diverting it towards un-swept areas. Additionally, PAM can also reduce the permeability of certain types of rocks, which helps to prevent the injected water from bypassing the oil and traveling straight through the formation. Overall, the use of PAM in tertiary oil recovery has proven to be an effective way to recover more oil from mature fields and extend the life of existing wells.