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Yes connate water saturation (Swc) is also described as irreducible water saturation, which is the result of oil or gas moving into a reservoir sand (process called drainage) to remove as much brine as possible. Initially the reservoir only contains formation brine and the oil or gas flushed the brine to a minimum saturation so that only an irreducible percentage Sw remains. In sands that are "wetted" by water rather than "wetted" by oil, the connate water saturation can be greater than 20% and for oil wet rock Swc can be less than 15% that is in good porosity clean sands. When the sand is tighter the connate water saturation Swc will be larger than 20% e.g. 30-40% leaving less of the pore space fraction for hydrocarbons.