ABSTRACT

Rocks can be classified as "Archie" or "non-Archie" depending on the relationship between pore geometry, resistivity, and porosity. A mathematical model (such as Archie's equation) which appropriately describes the conduction of a specific rock depends on the conduction mechanism. The conduction mechanism, in turn, is determined by pore geometry as well as non-geometric factors such as wettability and the presence of conductive or surface conductive minerals. An understanding of the relationships between pore geometry, conduction mechanisms, and conductivity models is critical for proper formation evaluation from logs. The concept of electricaltortuosity can be used to understand conductivity models such as Archie's equation. However, the electrical tortuosity, as a factor relating pore geometry and conductivity, is ambiguous in that the pore geometry cannot be inferred from the tortuosity alone.

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