CT-Based Core Heterogeneity Evaluation: Exploring Insights for Dual-Energy CT Rock Typing and SCAL Sampling Strategies

Abstract Advancements in X-ray computed tomography (CT) have enabled more precise, non-destructive characterization of core heterogeneity, which is essential for detailed core characterization and representative routine and Special Core analysis (SCAL) sample selection. This study presents a comprehensive evaluation of 35 diverse calibration rock samples, including clastics, carbonates, shales, and solid standards, using whole-core X-ray CT imaging. Statistical measures such as Heterogeneity Index (HI) and Coefficient of Variation (CV) were applied to quantify inter- and intra-slice variability, revealing distinct heterogeneity patterns related to lithology and mineralogy. Complementary XRD and XRF analyses were used to investigate the influence of elemental composition—particularly effective atomic number (Zeff)—on CT responses. The results underscore the critical role of compositional calibration in dual-energy computed tomography (DECT) rock typing models and introduce tailored trendlines for sandstone, limestone, and dolomite to enhance porosity prediction accuracy. This work contributes a robust framework for the selection of calibration standards, 3D heterogeneity quantification, directly supporting the development of DECT-based rock typing models, and the optimization of SCAL sampling strategies.