Application of complementary methods for more robust characterization of sandstone cores

Abstract

This paper is based on detailed mineralogical, structural, petrophysical, and geochemical studies of sandstone core samples, using routine core analysis methods. These include X-ray computer tomography (CT) scanning, magnetic resonance imaging (MRI), particle size analysis, point counting based on petrographic thin sections, environmental scanning microscopy (ESEM), X-ray diffraction (XRD), and X-ray fluorescence (XRF). In this study, we demonstrate the feasibility of combing these complementary methods in the characterization of reservoir properties of sandstone cores. Four types of sandstones (Slick Rock Aeolian, Fife, Locharbriggs, and Berea sandstones) that differ in grain size, porosity, and mineralogy have been characterized. The results of the different methods used were found to be consistent with each other, but the combination of a variety of methods has allowed a fuller characterization of the rock samples than each method used on its own, bringing out subtle variations in petrographic characteristics that add significant value towards a better description of reservoir properties. For example, it becomes apparent that some types of rocks like Berea sandstones thought to be homogeneous are in fact heterogeneous. The recognition that rock heterogeneity at the sub-centimeter scale may have a significant effect on hydrocarbon recovery requires that field-scale reservoir models take account of these small-scale effects in order to lay claim to reasonable accuracy in production forecasts.