Advances in theory and technology of non-marine shale oil exploration in China

Non-marine shale oil is a new frontier. Recent exploration practices have made significant progress in different shale formations including in the Ordos Basin, Songliao Basin, Bohai Bay Basin, Junggar Basin, and Qaidam Basin. At the end of 2022, the geological reserves of shale oil, including the proven, controlled, and predicted reserves, reached 44×10⁸ t, and the production in 2022 was 318 ×10⁴ t. The exploration theory and technology of shale oil have also made a series of advances, such as innovating shale experimental testing and analysis technologies including organic matter type analysis and organic matter generation and expulsion experiments, reservoir characterization technology, shale oil occurrence state and oil content analysis, and pressure maintaining coring and on-site testing. These technologies can basically meet the requirements of shale oil related experimental testing. A series of new understandings has been obtained in the aspects of fine-grained sedimentation and organic matter enrichment mechanisms, terrestrial shale laminated structure and combination types, pore and fracture structure and storage capacity in reservoirs, and shale oil enrichment mechanisms, which guided the research on evaluation of selected areas and zones in the key areas of shale oil. Technologies such as logging evaluation of hydrocarbon source rock quality, reservoir quality, and engineering quality, analysis and quantitative prediction of rock physical sensitive parameters, multi-task learning of reservoir parameter prediction, anisotropic stress prediction, seismic geological orientation evaluation of horizontal wells, and comprehensive evaluation of enrichment layers (“sweet spots”) have been developed and promoted. This provides important and all-cycle technical support for shale oil reserves submission, sweet spot area selection, horizontal well deployment, and directional drilling warning and engineering retrofit after drilling completion. However, large-scale exploration and efficient development of non-marine shale oil still face many challenges. It is necessary to establish new research content and priorities, especially to upgrade research precision and strengthen microscopic research, solid/liquid/gas multiphase and multi-field coupling flow mechanism research, and interdisciplinary research, in order to establish a new discipline of shale oil accumulation.