The Induced Polarisation (PI) is an electric phenomenon that occurs inside of material media in the time domain, with the release of stresses upon the interruption of a flow of electric current of step type (in this case, it is measured as chargeability) and also in the frequency domain, with a precise dispersion law of the electric resistivity upon the variation of the frequency of an alternated current flow. A PI source is connected to the oxido-reductive processes along the interface between the metal grains and interstitial fluids (electrode polarisation). Another important PI source consists instead of ionic accumulations in moving electrolytes due to mobility variations along the path (electro-kinetic polarisation). The tomographic inversion of the data obtained on the surface returns the ground in “output” based on chargeability images, thanks to which it is possible to identify possible accumulation areas or significant concentrations of hydrocarbons. The chargeability is proportional to the charge stored by the lithotype and it represents the concentration of a conductor in the multi-electrode area.