Permeability estimation using relaxation time spectra derived from differential evolution inversion

Permeability is an important indicator for reservoir evaluation, but there is no common model for permeability estimation at present. In this study, we have firstly briefly introduced the principle of time domain-induced polarization, and derived the relationship between relaxation time and pore diameter from the diffusion concentration distribution of pore fluid ions. Then the differential evolution algorithm was used to derive relaxation time spectra from the polarizability decay curve. Finally, a new integrated model with relaxation time spectra, porosity and formation factor was proposed to predict permeability. The results of the numerical simulation declare that the inversion accuracy of the differential evolution algorithm was clearly superior to the traditional singular value decomposition method, and the signal-to-noise ratio had little influence on the differential evolution algorithm. The results of permeability estimation from core samples indicate that the integrated estimation model proposed in this study could improve the accuracy of permeability estimation remarkably.