Formation Factor LAMBDAs
Archie's general formation factor and the Humble sandstone form.
2 lambdas
PO.PP.F.Archie(a, Phi, m)
Formation resistivity factor from Archie's equation. It is the ratio of the resistivity of a rock fully saturated with water to the resistivity of that water, expressed through porosity. F = a / φ^m. Porosity is a fraction. a and m come from a log-log plot of F against porosity, or from a named pair such as Humble.
PO.PP.F.Humble(Phi)
Formation resistivity factor for sucrosic sandstones from the Humble equation. It is Archie's equation with a = 0.62 and m = 2.15, the pair Winsauer, Shearin, Masson and Williams fitted at Humble Oil. F = 0.62 / φ^2.15. Porosity is a fraction, not a percent.