Characterizing strength and location of continental oil shale with drilling process monitoring in Southern Ordos Basin, China

The increasing demand for unconventional oil and gas resources, especially oil shale, has highlighted the urgent need to develop rapid and accurate strata characterization methods. This paper is the first case and examines the drilling process monitoring (DPM) method as a digital, accurate, cost-effective method to characterize oil shale reservoirs in the Ordos Basin, China. The digital DPM method provides real-time in situ testing of the relative variation in rock mechanical strength along the drill bit depth. Furthermore, it can give a refined rock quality designation based on the DPM zoning result (RQD(VDPM)) and a strength-grade characterization at the site. Oil shale has high heterogeneity and low strata strength. The digital results are further compared and verified with manual logging, cored samples, and digital panoramic borehole cameras. The findings highlight the innovative potential of the DPM method in identifying the zones of oil shale reservoir along the drill bit depth. The digital results provide a better understanding of the oil shale in Tongchuan and the potential for future oil shale exploration in other regions. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).