Abstract:  Continental shale oil in the Sichuan basin is currently an important new frontier for unconventional oil and gas exploration. The Lianggaoshan Formation in the Fuling area is the high-yield interval of continental shale oil in this region, and clarifying its sweet spot characteristics can provide insights for shale oil exploration and development in southeastern Sichuan. To investigate the sweet spot characteristics of continental shale oil in Lianggaoshan Formation of the Fuling area, Sichuan basin, this study conducted organic and inorganic geochemical tests and microscopic observations, and established a sweet spot evaluation method for continental shale in Lianggaoshan Formation by integrating sedimentation, reservoir formation and hydrocarbon accumulation. The results show that the sweet spots in Lianggaoshan Formation of the Fuling area exhibit the “four-high” characteristics: High total organic carbon (TOC) abundance, high porosity, high permeability, and high hydrocarbon content. The sweet spot intervals mainly develop organic-rich mixed mudstones and organic-rich argillaceous mudstones; The pore types are dominated by inorganic pores, followed by organic matter pores, and pores are mainly developed in solid bitumen, clay minerals and solid bitumen-clay mineral complexes. The sedimentary environment of sweet spot sublayer 3 is weakly oxidizing to weakly reducing, while sweet spot sublayer 4 experienced a reducing environment in the early stage and a weakly oxidizing to weakly reducing environment in the late stage. The formation and enrichment of shale sweet spots in Lianggaoshan Formation are controlled by three major factors: Sedimentary environment, lithofacies-mineral composition, and lamination development. In summary, a genetic model for continental shale development in Lianggaoshan Formation of Fuling area is established, revealing that the sweet spot intervals of Lianggaoshan Formation in the study area are mainly developed in semi-deep to deep lacustrine facies.

Key words: matrix-type continental shale oil, sweet spot reservoir, Lianggaoshan Formation, Middle Jurassic, Fuling area, Sichuan basin