EVALUATING THE PERFORMANCE OF MODELS FOR MATRIX PERMEABILITY ESTIMATION FROM COMPLEX RESISTIVITY MEASUREMENTS AT TWO SEDIMENTARY ROCK SITES

Spatially extensive estimates of permeability remain challenging to acquire using conventional borehole hydraulic tests at a scale to resolve matrix permeability values. Geophysical measurements are sensitive to the pore geometry controlling fluid flow and provide opportunities for indirect estimation of permeability from continuous measurements acquired in boreholes. The spectral induced polarization (SIP) or complex resistivity (CR) geophysical method provides information on a length-scale related to pore or grain diameter and the tortuosity of the interconnected porosity of the matrix, representing matrix permeability values. We tested a model for permeability prediction using CR on intact core samples obtained from two sedimentary rock sites. We acquired surface area measurements by nitrogen gas adsorption using the Brunauer–Emmett–Teller (BET) method, pore size distributions from mercury injection capillary pressure (MICP) porosimetry and gas permeability following ASTM D4525. The results demonstrate the sensitivity of CR to the pore geometric properties controlling fluid flow but show that the model requires calibration of fitting parameters that vary depending on site lithology conditions. The findings indicate the need for further studies of the control of mineralogy and fluid chemistry on the interfacial polarization generating the CR response.