The dual-porosity model, A newly developed interpretation method for shaly sands

The dual-porosity model has recently been developed by Total-Compagnie Francaise des Petroles for the determination of water-saturation in hydrocarbons-bearing shaly reservoirs form wholly log-derived data. It is operated by use of an equation whereby the influence of the clay content of the reservoir rock onto the formation resistivity is interpreted through modern theories of cation-exchange conductance. By taking advantage of the concepts applied to the elaboration of the dual-water model, the equation relates the amount of clay-bound water in the reservoir to the total and effective porosities determined by interpretation of conventional logs. On the other hand the equation applies to the bound-water specific volume a geometrical factor which is different from that affecting the effective porosity. Hence the appelation of dual-porosity model.