Reservoir Characterization Derived from Multiple Advanced Logging Techniques for Both Vertical and Horizontal Wells of Lacustrine Shale Oil Reservoir in China

Abstract Marine shale gas reservoirs in China have been developed for over 15 years, with operators seeking high-quality reservoirs in kerogen-rich source rocks. However, lacustrine shale oil reservoirs often do not exhibit the same favorable characteristics, as kerogen-rich source rocks are not always synonymous with good reservoirs. Permian lacustrine shale oil reservoirs are marked by complex mineralogy, low to medium kerogen content, low porosity, and diverse fracture types. Reservoir characterization to identify sweet spots is crucial for further exploration and development. One key factor to consider in shale oil reservoir characterization is the source-reservoir configuration. We propose an integrated solution that employs two-dimensional nuclear magnetic resonance (2D NMR) logging, advanced spectroscopy, borehole micro-resistivity imaging, and dipole acoustic measurements to characterize shale oil reservoirs. This comprehensive approach, which includes source rock analysis, reservoir movable oil volume and oil saturation, fracture effectiveness, and brittleness, provides valuable insights into the potential sweet spots from petrophysical and engineering point of view. This paper presents a case study of vertical polit well in together with its horizontal well drilling in the shale reservoirs of Fengcheng formation. In vertical well, an artificial intelligence method derived from the concept of blind source separation was proposed to extract signals from 2D NMR T1-T2 measurements. The producible hydrocarbon volume and its oil saturation obtained from 2D NMR plays a crucial role in the concept of source-reservoir configuration. Spectroscopy-derived total organic carbon (TOC) in shale ranges from 0.5% to 3.5%, with kerogen-rich source rocks having TOC values above 1.5%. Kerogen-rich shale with high movable hydrocarbon saturation is identified as a potential sweet spot. Additionally, tight sandstone (with porosity between 2% and 5%) containing underlying kerogen-rich shale can also be considered a potential sweet spot due to its typically high movable hydrocarbon saturation (above 60%). For inclined and horizontal wells, borehole micro-resistivity images measurements were utilized to analyze fracture development. The formation of fractures was primarily controlled by tectonic movements, with the fracture orientation closely aligned with the large strike-slip faults in the field. Regions with well-developed fractures usually exhibit higher hydrocarbon yields. This paper discusses the novel application of advanced logging measurements in lacustrine shale oil reservoirs. The petrophysical properties derived from logging are consistent with core experiment results. The source-reservoir configuration aids operators in assessing the potential of these reservoirs. The areas identified as potential sweet spots using the source-reservoir configuration concept show promising oil and gas production potential.