Petrological characteristics and shale oil enrichment of lacustrine fine-grained sedimentary system: A case study of organic-rich shale in first member of Cretaceous Qingshankou Formation in Gulong Sag, Songliao Basin, NE China

Bo LIU,Jiaxin SHI,Xiaofei FU,Yanfang LYU,Xianda SUN,Lei GONG,Yunfeng BAI

Table 1 Characteristics of lithofacies types in the Qing-1 Member of Gulong Sag.

No. Lithofacies Core characteristics Microscopic characteristics Sampling location and characteristics description TOC/% Mineral composition/% 1 High TOC laminated clayey mudstone Well H53, 2180.5 m, black, composed of mud-grade clay minerals, with rich lamellations and high TOC >5.0 Clay >45 Feldspar and quartz <30 Carbonates <20 2 High TOC massive siliceous mudstone Well H29, 2 109.2 m, black, composed of mud-grade quartz, feldspar and clay mineral, with massive structure and high TOC 2.0-5.0 Clay 30-45 Feldspar and quartz 50-70 Carbonates <10 3 Medium TOC massive siliceous mudstone Well H14, 1 957.4 m, dark gray, composed of mud-grade quartz, feldspar and clay minerals, with massive structure and high TOC 1.0-2.0 Clay 30-40 Feldspar and quartz 60-75 Carbonates <15 4 Medium TOC laminated siliceous mudstone Well H51, 2 202.3 m, interlayers of high TOC lamina and low TOC lamina 1.0-2.0 Clay 10-30 Feldspar and quartz 65-90 Carbonates <15 5 Low TOC laminated siliceous mudstone Well H53, 2 184.4 m, interlayers of clayey lamina and sandstone lamina 0.5-1.0 Clay 5-25 Feldspar and quartz 65-90 Carbonates with 5-25 6 Low TOC layered sandstone Well H51, 2 138.3 m, light gray siltstone, fine sandstone, and a small amount of clayey lamina and charcoal <0.5 Clay <15 Feldspar and quartz >85 Carbonates <10 7 Low TOC layered limestone Well H73, 2 321.7 m, black, dark gray, with obvious shell structure, limestone interbed cemented by carbonate <0.5 Clay <10 Feldspar and quartz <15 Carbonates >80