Which exponent in Archie's equation is associated with tortuosity?

Which exponent in Archie's equation is associated with tortuosity?

• A. n
• B. m
• C. k
• D. t

Answer: (A)

Archie’s law links formation resistivity to porosity, water saturation, and the properties of the pore network. The exponent that captures tortuosity is the one on the water saturation term: Sw raised to the negative n. This tortuosity exponent, n, describes how winding, less-direct current paths through the pore structure make resistivity rise as saturation decreases. In other words, as the conduction path becomes more tortuous, resistivity increases more rapidly for a given decrease in Sw. The cementation exponent, m, is a separate factor that reflects how pore geometry influences connectivity via porosity, and the constant a is a scaling factor. Therefore, the tortuosity is represented by the exponent on Sw, which is n.

Archie’s law links formation resistivity to porosity, water saturation, and the properties of the pore network. The exponent that captures tortuosity is the one on the water saturation term: Sw raised to the negative n. This tortuosity exponent, n, describes how winding, less-direct current paths through the pore structure make resistivity rise as saturation decreases. In other words, as the conduction path becomes more tortuous, resistivity increases more rapidly for a given decrease in Sw. The cementation exponent, m, is a separate factor that reflects how pore geometry influences connectivity via porosity, and the constant a is a scaling factor. Therefore, the tortuosity is represented by the exponent on Sw, which is n.