Time constants of induced polarization in water-saturated sands: Theory and experiments

The paper presents a theoretical description of Induced polarization decay In Ion-conductive rocks, which develops the steady-state model of Friedrich sberg-Sidorova based on the diffusion nature of Induced polarization. Grain contacts and pore space filled with interstitial liquid are regarded as na rrowing and broadening current conduits that are characterized by different transport numbers. An analytical solution of the unsteady diffusion equati on yielded an expression describing time constants of Induced polarization for a model In which wide pores are much longer than the narrow ones. Exper imental transient characteristics obtained for sands with different average grain sizes are consistent with the suggested theory. According to theoretical and experimental results, the time constant of ind uced polarization decay for pure sand is proportional to the square of its average grain size.