Base slide showing well/test zone profile. Blue is water, green is oil. In this case, the oil in the pore space is all pushed to the base of the zone to help illustrate the operation of a SWCT test. The well perforations are shown as the white broken line. In a residual oil setting, the oil is stationary in the pore space and the water is the mobile phase. The well produces water only but once produced oil in it’s history.