Controls of pore throat radius distribution on permeability

The purpose of this study is to present a model for the relationship between pore throat radius and permeability for reservoir rocks. These relationships are illustrated using sandstone and limestone reservoir rock petrophysical data from oil fields in Egypt and Arabian Gulf as well as from Saudi Arabia, Abu Dhabi and Kuwait. Mercury injection capillary pressure data was used to obtain measured pore throat sizes and the radii at different levels of mercury saturation and pore throat sorting. The pore throat size distribution (r(25), r(35), r(50) and r(75)) was found to be related to permeability. New empirical logarithmic law relationships are presented using these pore throat radii. The r(35) pore throat was found to be closely correlated to permeability and has the form of ln(K) = 1.71ln(r(35)) +1.9. The relationship work best for well sorted reservoir samples. Finally, the validity of the new model represented by porosity and (r(35)) was tested using 123 rock samples (sandstone and limestone). The estimated permeability using the new model was plotted against the measured permeability and revealing high coefficient of correlation.