The microscopic mechanisms of induced polarization relaxation time spectra in shaly sandstone

The relaxation time spectra of induced polarization in shaly sandstone has a wealth of information of formation. This paper established the mathematical-physical model of induced polarization based on serial capillary model, and the charging and discharging processes of induced polarization were simulated by numerical method. Meanwhile, the decay curve of induced polarization was inversed from the multi-exponential inversion by Levenberg-Marquardt. The influences of porosity, cation exchange capacity, concentration of solution, temperature, and discharging time etc. on the induced polarization relaxation time spectrum were analyzed. The result shows that relaxation time spectra is not only the expression of the microscopic pore structure in rock, but also the diffusion process of ion repristination.