This paper presents a novel pore-scale approach for the derivation of electrical properties of porous media. In this approach we create a digital porous medium on the basis of experimental grain-size distribution data and apply a drainage simulator based on pore-morphology analysis. Then we simulate via finite difference discretization the electrical charge flow within the two-fluid and solid pore-scale distributions, and derive the effective resistivity of the porous medium. Simulation results have been compared with resistivity data from a UK Permo-Triassic Sandstone (Sherwood S.). Agreement between measured and simulated bulk conductivities at different saturation values is excellent; this confirms the validity of the adopted approach, and its underlying assumptions.