Effect of pyrite on fluid distribution and permeability modelling of North Sea Lower Cretaceous clay rich carbonate reservoirs

In this study we investigate the fluid property and effect of the conductive nature of the mixed Sola and Tuxen formations found in the Lower Cretaceous clay rich carbonates in the Danish North Sea. From core measurements and log analysis we model the petrophysical properties allowing evaluation of fluid distribution and permeability in the studied succession.
We extend Archie`s equation for water saturation calculation using Hashin-
Shtrikman bounds and investigate the phase mixing in the formation, providing a consistent and practical method for saturation evaluation in mixed mineral heterogeneous formation containing conductive minerals.
We evaluate and compare controlling parameters for permeability calculation from spectral gamma ray, electrical resistivity, Nuclear Magnetic Resonance and sonic velocity logs and provide a practical approach for modelling permeability at the well log scale along with the obtained parameters for best fit according to each method.