We analyzed the influence of pore fluid composition on thecomplex electrical conductivity of three sandstones with differingporosity and permeability. The fluid electrical conductivity(σ_w) of sodium and calcium chloride solutions was graduallyincreased from 25 mS/m to 2300 mS/m. The expected linearrelation between σ_w and the real component of electricalconductivity (σ ") of the saturated samples was observed. Theimaginary component (σ " ) exhibits a steeper increase at lowersalinities that flattens at higher salinities. For a glauconitic sandstoneand a high porosity Bunter sandstone, σ " 0 approaches anasymptotic value at high salinities. Sodium cations result inlarger values of σ " than calcium cations in solutions of equalconcentration. Debye decomposition was used to determinenormalized chargeability (m_n) and average relaxation time (τ)from spectral data. The behavior of σ " is comparable to m_nas both parameters measure the polarizability. At lower salinity,the relation between m_n and σ_w approximates a power law withan exponent of ～0.5. The average relaxation time shows only aweak dependence on σ_w. The normalized chargeability of sandstonesamples can be described by the product of the pore spacerelated internal surface and a quantity characterizing the polarizabilityof the mineral-fluid interface that depends on fluidchemistry. We introduce a new parameter, the specific polarizability,describing this dependence. We propose relationsbetween polarizability and fluid chemistry that could be usedto estimate pore space internal surface across samples of varyingσ_w. We observe a consistent maximum polarizability for quartzdominated siliceous material.
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