The usual log response equations are of the form:
LOG = PHIe * Sxo * Lw (water term)
+ PHIe * (1 - Sxo) * Lh (hydrocarbon term)
+ Vsh * Lsh (shale term)
+ (1 - Vsh - PHIe) * Sum (Vi * Li) (matrix term)
WHERE:
Lh = log reading in 100% hydrocarbon
Li = log reading in 100% of the ith component of matrix rock
LOG = log reading
Lsh = log reading in 100% shale
Lw = log reading in 100% water
PHIe = effective porosity (fractional)
Sxo = water saturation in invaded zone (fractional)
Vi = volume of ith component of matrix rock
Vsh = volume of shale (fractional)