Abstract: To clarify the geological characteristics of shale oil in Fengcheng Formation, Urho District, Junggar Basin, this study analyzed the deposition and reservoir performance of the formation based on the core samples, thin sections observation, and geochemical characteristics data, and conducted a dual "sweet spots" evaluation integrating geological and engineering aspects in consideration of brittleness and oil content characteristics. The study results show that: the Fengcheng Formation was deposited in a hypersaline, anoxic, and reductive environment, with the main reservoir rock types being saline fine-grained mixed sedimentary rocks. These rocks exhibit complex longitudinal variations, strong heterogeneity, and significant vertical differences in organic matter content, have an average organic matter content of 1.22%, with type Ⅱ₁ kerogen being predominant, indicating a mature to over-mature stage with high hydrocarbon generation potential under saline conditions. The reservoir spaces in Fengcheng Formation are primarily dissolution pores and micro-fractures, accounting for 40.00% and 39.45% respectively, characterized by fine skewness, poor sorting, large variations in displacement pressure, and high median pressures, typical of low porosity and low permeability tight reservoirs. The main oil-bearing rock types are laminated dolomitic mudstones and argillaceous dolomites. The first class "sweet spots" are characterized by high brittleness, large oil-bearing area, good physical properties, and a high degree of fracture development, mainly distributed at the bottom of the second and third sub-members of Fengcheng Formation, and at the middle and upper parts of the second sub member, the second class "sweet spots" bed primarily develops. The findings of this study have guiding significance for the development of shale oil in Fengcheng Formation of Junggar Basin.

Key words: sedimentary environment, shale oil, reservoir characteristics, "sweet spot"prediction, Fengcheng Formation, Urho District, Junggar Basin