A theoretical and experimental study on electric resistivity of vuggy fractured media is presented. In order to have a rigorous control of the involved variables, a vuggy fractured medium is idealized by a cubic array of cubes having hemispherical cavities drilled in each cube face. In this model, the spaces between the cubes represent fractures and the hemispherical cavities represent vugs. The theoretical developments lead to a simple relationship expressing formation resistivity factor as the product of two factors, one depending on vug porosity and the other on fracture porosity. This formulation has been validated with experimental data obtained with a special resistivity cell. The proposed formulation can easily be generalized to be applicable to real rocks, and so it is a useful tool for interpretation of electric well logs of vuggy fractured formations.

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