Geological control of electrical behaviour and prediction key of transport properties in sedimentary porous systems

The paper reports an investigation of porous solid structure effects on their electrical behaviour at different frequencies and gives the permeability prediction from the electrical behaviour of sedimentary porous systems. The electrical conductivity of a porous solid depends on different parameters such as the spatial distribution of the constituent minerals and pore space, saturation distribution, mineralogical content, wettability and temperature. Not only the transport properties such as the electrical conductivity and permeability depend on porosity but they are also strongly sensitive to the micro-structure of the porous system, the connectivity of the pore space and their micro-geometry. The electrical behaviour of porous solids can be explained by different parameters such as: the formation resistivity factor, the cementation factor, the resistivity index and the saturation exponent. The saturation exponent n depends strongly on the frequency and ranges between 1.2 and 3.4. A non-linear behaviour is observed. This is due to the high microporosity development and its roughness. The highest value of n is obtained for karstic dolomite textures. The frequency dispersion is explained by the chargeability factor M which depends strongly on the sedimentary rock texture, the brine/gas saturation of porous solids and salinity of brine. The highest value of the chargeability factor is observed in mudstone–wackestone textures while the lowest value is reached in the dolomitic crystal carbonate texture. One of the most important conclusions that has emerged is that the permeability may be estimated by combining the electrical behaviour properties such as the formation factor with the micro-geometric length scale such as the pore size, throat size or the grain size.