Resistivity porosity

Determining porosity from a resistivity log is not a straight forward job. A lot of knowledge gained from the petrophysics parameters of the field is required in order to have a good estimation of this property. Additionally, all proposed models are based on clean formations (clean sands), and Archie’s water saturation equation, which is widely used in the industry. After some combinations and assumptions (m:2, n:2 and a:1) porosity can be related with resistivity and saturation, as you will see in the equation below:

∅=√(R_W )/(S_W) ×1/√Rt

Where Rw is the formation water resistivity, Rt is the resistivity from the formation, Sw is the water saturation which means that in a water saturated formation, Sw:1.

This calculation can only be used in the Property Calculator and cannot be specified as the user-defined equation on the Validate Rock Types form.