Experimental quantification of thermal signatures in rock fragmentation and a geothermal-assisted thermal-response method for real-time rock strength and temperature identification

Heat from drill bit-rock interaction serves as an inherent thermal signature for formation lithology identification. While existing studies predominantly focus on cutting teeth thermal damage and bit life prediction, the dynamic evolution of rock fragmentation heat (RFH) and its coupling mechanism with lithological properties have not yet been fully elucidated. In this study, micro-drilling experiments were conducted on cement mortar specimens with varying uniaxial compressive strengths (UCS) using an independently developed comprehensive temperature monitoring system. The coupled effects of rock strength, heterogeneity, and drilling parameters on cutting tooth temperature were quantitatively investigated. A predictive model correlating rock UCS with average cutting tooth temperature was established and validated on natural sandstone specimens, achieving a high fitting accuracy ( R 2 =0.981). Key findings reveal that lithological interfaces induce distinct temperature jumps, confirming the efficacy of RFH signals in real-time lithological characterization. Rock UCS exhibits a positive correlation with RFH intensity; both rotational speed and penetration rate are positively correlated with temperature rise, with rotational speed exerting a more dominant effect; weak interlayers trigger significant temperature drops, with the drop amplitude showing a linear negative correlation with interlayer UCS. Building on these insights, we propose a real-time lithology monitoring methodology, enabling synchronous inversion of formation lithology and bottom-hole temperature via drilling fluid thermal-hydraulic flow analysis. This work provides a novel technical framework and experimental basis for optimizing drilling operations and high-resolution formation evaluation.