Abstract: The shale oil in Mahu sag, Junggar Basin is the alkaline (salty) lake type shale oil found in China, which is of great significance for unconventional oil and gas exploration and reservoir research. Based on the data of core, thin section, scanning electron microscopy (SEM), geochemistry and imaging logging, the paper qualitatively and quantitatively evaluates the lithofacies and reservoir property, occurrence state of organic matter, and development value of Permian Fengcheng Formation. The lithofacies identification criteria of fine-grained sedimentary rocks in Fengcheng Formation have been established according to mineral composition and fracture development characteristics. It can be divided into three types of lithofacies, i.e., fractured felsic fine-grained lithofacies (Type Ⅰ), laminated mixed fine-grained lithofacies (Type Ⅱ) and laminated cloud (ash) lithofacies (Type Ⅲ). Type I dominated by terrigenous input plays a dominant role. It has good physical reservoir property, dual media of soluble pores and micro-fractures, well-developed macropores and macropores of more than 50%, pore structure with moderate-good distortion, and high oil saturation index, boasting of high commercial development value. Type Ⅲ is a superior lithofacies with commercial development value, while Type Ⅱ is a general lithofacies with mining value. The MY1 well test has achieved a stable and high-yield industrial oil flow, 75% of which is contributed by the fractured felsic fine-grained lithofacies.

Key words: lithofacies, terrigenous input, endogenous deposition, shale oil, alkaline lake basin

摘要： 准噶尔盆地玛湖凹陷页岩油是碱湖型页岩油，对于非常规油气勘探与储层研究具有重要意义。综合利用岩心、岩石薄片、扫描电镜、地球化学、成像测井等资料，对玛湖凹陷二叠系风城组岩相储集性能、有机质赋存状态和开发价值进行了定性、定量评价。依据矿物组分和裂缝发育特征，建立了风城组细粒沉积岩岩相判识标准，划分出裂缝长英质细粒岩相、纹层混合细粒岩相和含纹层白云质/灰质岩相3种岩相。以陆源输入为主的裂缝长英质细粒岩相是优势岩相，其储层物性好，具有溶孔-微裂缝型孔隙结构类型，宏孔和宏观孔占50%以上，具有好—中等歪度的孔隙结构，含油饱和度指数高，具有较高商业开发价值。含纹层白云质/灰质岩相是具有商业开发价值的较优势岩相。纹层混合细粒岩相是具有开采价值的一般岩相。MY1井在试油中获得了稳定高产工业油流，其中，裂缝长英质细粒岩相的贡献占75%。

关键词: 岩相, 陆源输入, 内源沉积, 页岩油, 碱化湖盆