What are the differences of initial water saturation assumpt

What are the differences of initial water saturation assumptions when dealing with \"preserved core plugs\" and \"Cleaned core plugs\"?

Solution

1. When native-state or preserved core plug samples are used, it is assumed that these samples already have established irreducible water saturation. However, when cleaned core samples are used, the value of irreducible water saturation needs to be established in the sample before relative permeability testing,

2. Preserved core plug samples are used in order to maintain reservoir wettability so that the relative permeability data measured are representative of reservoir wettability, the initial water saturation determined from the plug-end trim is assumed to represent the initial water saturation in the entire core plug sample whereas  in cleaned core plug, the condition at which the water saturation is carried out depends on the choice of test conditions: room, partial, or complete reservoir condition tests using reconstituted or actual formation brine and after the core plug is fully saturated with water, the absolute permeability of the sample is determined using Darcy’s law