The Relationship Of Electrical Resistivity To Intergranular Permeability In Reservoir Rocks

A re-examination of resistivity-permeability relationships for diverse reservoir sands has indicated that the actual form of these relationships is controlled by the level of shale effects manifest in the electrical data. Furthermore, by considering a broad behavioral framework of shale effects itis demonstrated that a water-saturated reservoir rock can show either a positive or a negative relationship between permeability and resistivity parameters, or no relationship at all, according to local petrophysical conditions which can be readily identified. The explanation of this paradoxin terms of manifest shale effects seems to be valid for the entire range of water salinities that can be encountered in natural granular systems. A tripartite subdivision of the field of values of excess conductivity and electrolyte resistivity makes it possible to predict the form of formation factor - permeability relationships for any water-saturated granular rock, provided that these petrophysical indicators have been correctly evaluated at the outset. By this means the relationship of formation resistivity factor to permeability is seen to be more systematic than has hitherto been evident. This approach can be extended to hydrocarbon-bearing media but its practical application might be prohibitively difficult. It has immediate implications for correlation exercises which specify intergranular permeability as the intended predict and.