Petrophysical characterization of Lower Cretaceous marly chalk through ¹H-NMR and complex conductivity

Complex conductivity and T₂ relaxation time spectra were acquired in ten marly chalk samples from Lower Cretaceous and one outcrop chalk sample from Upper Cretaceous. The results demonstrated that the quadrature conductivity spectrum provides information on pore space geometry similar to the T₂ relaxation time domain. Sample conductivity was lower in samples showing higher quadrature conductivity at lower electromagnetic frequency. Deriving chargeability by a Cole-Cole model, we identified that chargeability increases with the increase of specific surface area of the total volume. This finding has implications for well-logging techniques that derive matrix permeability information using electrical conductivity measurements at distinct frequencies. In conclusion, this study highlights the potential of complex conductivity and chargeability measurements, along with applying Kozeny's equation, to provide valuable information on pore space characteristics and matrix permeability. This information can enhance our understanding of subsurface formations and aid in reservoir characterization and hydrocarbon exploration efforts.