Core Characterization and Sample Selection in Heterogeneous Formations

Abstract

Summary Detailed reservoir core characterization is often overlooked in the sampling process for core analysis measurements. Random core sampling is usually performed and the selected plugs are often not associated with proper rock types or the reservoir heterogeneity. This leads to unrepresentative selection of the core samples and raises questions about the effectiveness of the core data in reservoir models and their calibrations. In this study, a robust sampling strategy was followed in reservoir cores from two heterogeneous formations in Kuwait. The objective of the core sampling was to obtain representative plugs for petrophysical and fluid flow analyses that would support dynamic model predictability. The sample selection criteria were based on statistical distribution of litho-types in the core to ensure optimum characterization of the main reservoir units. The litho-types were identified based on porosity and mineralogy variations along core lengths utilizing advanced dual-energy X-ray CT scanning. This technique provided high resolution data at 0.5mm spacing to detect all variations in the core. Different porosity cut-offs were assigned for each mineralogy, which resulted in precise identification of the lithotypes in the core.