Abstract:

Well-Ji-174 is an exploration well with the longest core extraction and the most data in the shale oil reservoir of Lucaogou Formation in Jimusar sag, Junggar Basin. The establishment of the “iron pillar” is of great significance to the studies of the shale oil longitudinal characteristics. It is found that the lithology of reservoir is mainly transitional lithology mixed with clastic rock and carbonate rock, and changes quickly in the longitudinal direction. The lithofacies reflects the semi-deep to deep lacustrine sedimentary environment with gradually deepening upward water body. The average porosity and permeability of the reservoir are 11.1 % and 0.056×10^-3 μm², respectively, which make the reservoir presents the characteristics of medium-low porosity, low-permeability and ultra-low permeability. The dolomite and sand content of the reservoir are positively correlated with the physical property and oil content. The upper and lower sweet spots are developed. The main lithology of the upper sweet spot is clastic dolomite, allowing the formation of the reservoir space with developed dissolution pores and a thickness of 24 m. The main lithology of the lower one is fine siltstone, dolomite sandstone and dolomite siltstone, whose reservoir space with thickness of 35 m is mostly fissures and pores. The favorable area of these two sweet spots covers an area of 1 299 km², indicating that the shale oil in Lucaogou Formation has large-scale exploration potential.

Key words: shale oil, sweet spot, geological characteristics, Lucaogou Formation, Junggar Basin