Wettability alteration mechanism is still believed to be the main contributor to low salinity water Injection (LSWI) effect on oil recovery from carbonate rocks. This paper makes an attempt to explain the double electric layer expansion as a main mechanism and contributor to LSWI effect on oil recovery from carbonate rocks. The existence of double electric layer expansion mechanism in carbonate rocks is investigated through history matching recently published coreflood experiments using the wettability alteration option in the UTCHEM simulator. The history match results suggest that wettability alteration has negligible effect on water relative permeability. The negligible change in the water relative permeability is also consistent with the double electric layer expansion whereas the immobile water film thickness increases and hence the relative permeability remains constant. This paper provides a basis to develop a LSWI model to predict oil recovery from carbonate rocks.