Analysis of porosity parameter with involvement of elements of regional petrophysics (electrofacies) and clayness type

The most important estimation parameter - the open porosity coefficient (Kp) - in petrophysical laboratories is, as a rule, determined for the productive formation on the whole and without taking into account its regional heterogeneity. As a basic criterion at selecting the samples to construct the model Rp = f(Kp) a range of the porosity value is taken. In this case it is assumed that the higher is Δ Kp, the higher is the validity of the relation Rp = f(Kp). However, in practice such concept often creates the problems of ambiguity in determining the porosity by the electric resistivity of water saturated samples in different wells even within one field. This phenomenon is resulted from neglecting, on one hand, the specific features of the regional petrophysics object - facies, which are reflected in the form of well logging curves including SP, and, on the other hand, the element of the general petrophysics object - a type of clayness. The breakdown (classification) of the formation by facies, determination and taking into consideration the type of clayness as well as distinguishing and analysis of petrophysical types of rock based on the rock porosity and permeability characteristics within a formation permit to obtain satisfactory relations between electric resistivity and porosity of the rock.