On the estimation of specific surface per unit pore volume from induced polarization: A robust empirical relation fits multiple data sets

摘要

We analyze the relationship between induced polarization (IP) parameters and the specific surface area normalized to the pore volume (S-por) for an extensive sample database. We find that a single linear imaginary conductivity-S-por, relation holds across a range of single-frequency PP data sets composed of sandstones and unconsolidated sediments that lack an appreciable metallic mineral content. We also apply a recent approach defined as Debye decomposition (DD) to determine normalized chargeability (m(n)), a global estimate of polarization magnitude from available spectral IP (SIP) data sets. A strong linear relationship between m(n) and S-por is also found across multiple data sets. However, SIP model parameters determined for samples containing metallic minerals are approximately two orders of magnitude greater than for the model parameters estimated for the nonmetallic sample database. We propose a concept of "polarizability of the mineral-fluid interface per unit S-por" to explain this difference, which is supported by the observed dependence of IP parameters on fluid conductivity between sample types. We suggest that this linear IP-S-por relation can be considered the IP equivalent of the classical Archie empirical relation. Whereas the Archie relation describes a power-law relation between electrical conductivity due to electrolytic conduction through the available interconnected pore volume, the IP-S-por relation is an equivalent relation between mineral-fluid interfacial polarization and available pore surface area.