Residual Oil Saturation
The fraction of pore volume occupied by oil at the end of oil displacement using a specific fluid (ROS). It signifies the ultimate recovery under a given displacement process and represents the end point of relative permeability curves. It is the saturation achieved after an infinite number of pore volumes of displacing fluid have flowed through the rock. Depends on flow rate, permeability, capillary end effects, test methodology, and the test laboratory.
