Theoretical study of the dielectric constant in porous sandstone saturated with hydrocarbon and water

Porous sandstone reservoirs generally consist of three components: sand grains, hydrocarbons, and water. This paper proposes a hybrid method to predict the effective dielectric constant of such reservoir rocks using a combination of existing formulas and a simplified Fourier expansion method. Taking into consideration fluid distribution in pore space as well as pore structure, we have obtained the relations between the effective dielectric constant of sandstone and water saturation. The calculation results indicate that the effective dielectric constant of sandstone varies as a function of the water saturation when porosity is above 10%, but it cannot predict well the hydrocarbon content in sandstone with low porosity (/spl les/10%). In this study, two different cases are discussed. In the first, water is continuous and oil is in dispersed form in pore space, and in the second, oil is continuous and water is as a dispersed phase in pore space. Very different results are obtained from the two distributions. In Case 1, the effective dielectric constant approximately linearly increases with water saturation, but in Case 2, it is seen that a typical nonlinear relationship exists between the effective dielectric constant and water saturation. Furthermore, three models with microgeometry are considered, and the calculating result shows that the influence of geometry on the effective dielectric constant is large.