Geochemical characterization and evaluation of shale oil bearing characteristics of Permian Pingdiquan Formation in eastern Junggar Basin

Abstract

Of the Permian Pingdiquan Formation in eastern Junggar Basin, western China, the continental shale oil is the principal prospective unconventional resources target. Our research described the analysis on core samples from the Permian Pingdiquan Formation in eastern Junggar Basin. Geochemical technologies, like contents of total organic carbon (TOC), Rock-Eval pyrolysis, and clay mineral identification through X-ray diffraction (XRD), were analyzed on the specimens. Shale oil bearing characteristics were deeply dissected through two-dimensional nuclear magnetic resonance (2D NMR) and the quantitative grain fluorescence on extract (QGF-E) technology. The results indicated that the source rocks of the Pingdiquan Formation in Qitaizhuang area possessed an elevated abundance of organic matters meeting the criteria of high-quality source rocks. However, the Mulei sag and Shiqiantan sag developed medium-poor source rock segments, which mainly due to the high paleo-productivity of source rocks in Qitaizhuang area. The combination of high-frequency QGF and 2D NMR can analyze the content of shale oil in shale reservoirs. The oil saturation in Qitaizhuang area was higher than Mulei sag and Shiqiantan sag. MAX-EX/MAX-EM and R1 indicated that the oil density and viscosity in Qitaizhuang area was higher than other areas. This further proved that the oil in Qitaizhuang area was from near source, while the oil in Shiqiantan and Mulei sag was from fruther source. The oil content of shale reservoir in eastern Junggar Basin was controlled by the overall organic carbon content and its pore throat construction. Our research lays a foundation for shale oil exploitation exploration in the Permian Pingdiquan Formation of eastern Junggar Basin.