Pore network modeling of thin water film and its influence on relative permeability curves in tight formations

•An improved pore network model for tight formation with consideration of thin water film is proposed.•The effect of the average pore size and pore shape on relative permeability and capillary pressure curves are investigated.•As the average pore radius is below 100 nm, the thin water film become non-negligible.•The mechanism of thin water film on oil–water two phase flow is investigated extensively.