The effects of pore structure on the electrical properties of sand-based porous media

Electrical properties are an essential indicator of petrophysics characteristics. This study seeks to deepen the understanding of the effects of pore structure on the electrical conductivity of sand-based porous media. Taking into account the effects of pore area heterogeneity and pore geometry heterogeneity, we improve the pore equivalent model and establish a new conductivity model for sand-based porous media. Experimental data of 39 sandstone samples, partial exhibits of non-Archie phenomenon, are analyzed to verify the new conductivity model. Results show that compared with the Archie model and equivalent rock element model, the new model has higher accuracy in evaluating essential parameters, i.e., formation factor and resistivity index. In addition, analyzed by the new model, four kinds of non-Archie phenomenon found in experimental data can be attributed to four major factors: strong pore area heterogeneity, strong pore geometry heterogeneity, dispersed n-values, and the fluid infilling transition from tubular-like pores to micro membrane-like pores. The new model can quantitatively characterize the effects of pore structure on the electrical conductivity of sand-based porous media and has certain guidance and reference significance for the research work of petrophysics, reservoir evaluation, etc.