Benchmark study using a multi-scale, multi-methodological approach for the petrophysical characterization of reservoir sandstones

Abstract

Abstract. This paper presents a detailed description and evaluation of a multi-methodological petrophysical approach for the comprehensive multiscale characterization of reservoir sandstones. The suggested methodology enables the identification of Darcy-scale permeability links to an extensive set of geometrical, textural and topological rock descriptors quantified at the pore scale. This approach is applied to the study of samples from three consecutive sandstone layers of Lower Cretaceous age in northern Israel. These layers differ in features observed at the outcrop, hand specimen, petrographic microscope and micro-CT scales. Specifically, laboratory porosity and permeability measurements of several centimetre-sized samples show low variability in the quartz arenite (top and bottom) layers but high variability in the quartz wacke (middle) layer. The magnitudes of this variability are also confirmed by representative volume sizes and by statistical anisotropy analyses conducted on micro-CT-imaged 3D pore geometries. Two scales of porosity variability are revealed by applying variogram analysis to the top layer: fluctuations at 150 μm are due to variability in the pore size, and those at 2 mm are due to the occurrence of high- and low-porosity bands occluded by iron oxide cementation. This millimetre-scale variability is found to control the laboratory-measured macroscopic rock permeability. Good agreement between the permeability upscaled from the pore-scale modelling and the estimates based on laboratory measurements is shown for the quartz arenite (top) layer. The proposed multi-methodological approach leads to an accurate petrophysical characterization of reservoir sandstones with broad ranges of textural, topological and mineralogical characteristics and is particularly applicable for describing anisotropy at various rock scales. The results of this study also contribute to the geological interpretation of the studied stratigraphic units.