Talk:Archie's law

Tortuosity and Formation factor

I think the equation should read:

$C_{t}=aC_{w}\phi ^{m}S_{w}^{n}$

or

$R_{t}={\frac {aR_{w}}{\phi ^{m}S_{w}^{n}}}$

where $a$ is the coefficient of tortuosity.

Also, it might be better to define Archie's formation factor as:

$F={\frac {a}{\phi ^{m}}}={\frac {R_{t}}{R_{w}}}$

Where Rt is the resistivity of the water saturated formation and Rw is the resistivity of the water inside that formation. There is no article for Formation factor so it would be a good idea to define it more broadly in this article. 38.100.75.194 (talk) 17:03, 22 February 2010 (UTC)

Thanks for your suggestions. I have incorporated them. Berland (talk) 14:31, 4 March 2010 (UTC)

I think that the first equation should read:

$C_{t}={\tfrac {1}{a}}C_{w}\phi ^{m}S_{w}^{n}$

if $a$ is really the tortuosity factor found elsewhere. This is consistent with a conductivity that decreases as tortuosity increases and also with the second equation above (assuming $R_{t}$ is ${\tfrac {1}{C_{t}}}$. Reference is also been made to a "lithology factor", but it is not clear that this is the same thing as tortuosity. Mrsylvestre (talk) 10:05, 21 March 2010 (UTC)

The equation in the article is already like you suggested. I could not find 'lithology factor' in the article, but I guess it has to be just another name for 'a', so I added it to the list of possible names. --Berland (talk) 10:22, 22 March 2010 (UTC)