A GRAIN CONDUCTIVITY APPROACH FOR WATER SATURATION ESTIMATION OF SHALY SANDS

Abstract

Estimation of in-place hydrocarbon reserves is essential starting from reserve accretion to development phases of a field. Water saturation is one of the key parameters for accurate reserve estimation among others. Although a majority of the clastic reservoirs across the world are shaly sands, theoretically robust and practically implementable models for water saturation estimation in these reservoirs are not available in literature. The models presently being used in the industry are either empirical or semi-empirical. The basin specific empirical models can not be applied to other basins. With the present practices and facilities being exercised in E & P industry, semi empirical models give qualitatively good results; however fail in quantitatively accurate estimation. Therefore, accurate estimation of in-place hydrocarbon reserves presents a big challenge for geoscientists. We have tried to solve this problem by proposing a new theoretical saturation equation through the modeling of the electrical conductivity response of shaly sands. This novel approach is developed based on effective medium theory and theory of mixtures. Further, examining the new model on experimental core data shows a very good fits and improved results over previously proposed theoretical models in literature. Being theoretical, the proposed equation can be applied to any basin across the globe for accurate water saturation estimations in shaly sand reservoirs.