High-resolution mechanical characterization of lacustrine shale oil reservoir in China based on scratch testing

The lacustrine shale oil reservoirs in China exhibit pronounced heterogeneity and anisotropy. Conventional approaches for characterizing shale mechanical properties—such as plug-scale mechanical testing and log-derived elastic estimates—provide only coarse resolution at meter-to-decimeter-scale. These methods lack the precision required to capture the fine-scale heterogeneity required for advanced geomechanical analysis. To address this limitation, we conducted scratch testing, uniaxial compression testing, and CT scanning on full-diameter core samples from the Yingxiongling area in the Qaidam Basin. This study investigates the principles and analytical methods of scratch testing and validates the approach for calculating continuous mechanical parameters along full-diameter cores. Key findings demonstrate significant strength variations among different lithofacies in the Yingxiongling area. Scratch testing successfully provides continuous profiles of uniaxial compressive strength and Young’s modulus across full-diameter cores. Furthermore, it visually identifies transition zones between lithofacies and reveals interlayer fracture locations within the core. This study establishes an efficient method for obtaining continuous, high-resolution mechanical parameters from full-diameter cores, offering theoretical and methodological support for enhancing the accuracy of mechanical property characterization in shale oil reservoirs. • High-resolution UCS and Young's modulus were derived from scratch testings on full-diameter cores and validated against uniaxial compression testings with <8% error. • Millimeter-scale strength variations from scratch testing correlate directly with CT-identified bedding and microfractures. • The method supports the construction of centimeter-scale, high-fidelity mechanical models of shale reservoirs.