准噶尔盆地玛湖凹陷二叠系风城组页岩油赋存特征与影响因素

综合应用地质、钻井、X衍射矿物成分分析、氩离子抛光-场发射扫描电镜-X射线能谱实验、高压压汞、岩石热解与岩心二维核磁共振实验，开展准噶尔盆地玛湖凹陷二叠系风城组页岩油赋存特征及其影响因素的研究。玛湖凹陷风城组页岩油主要存在薄膜状吸附油与充填状游离油2种赋存方式，岩相类型、岩石矿物组分与储集空间类型是页岩油赋存状态的主控因素。玛湖凹陷风城组发育4种岩相类型，分别为云质页岩相、砂质页岩-含云粉砂岩相、含碱矿白云岩-泥质粉砂岩相、硅化白云岩-云质粉砂岩相，不同岩相类型的矿物组分、储集空间类型、孔喉结构分布与页岩油微观赋存状态存在较大的差异。对比分析不同岩相类型可知，石英含量、黄铁矿含量、有机质含量与热解烃含量（S₂）存在正相关关系，长石含量、白云石含量与游离烃含量（S₁）呈弱正相关关系。游离油主要分布于中孔、大孔为主的次生溶蚀孔、残留粒间孔中，吸附油集中分布于中孔、中小孔为主的有机质孔、晶间孔与矿物颗粒表面。不同岩相类型的矿物组分与孔喉结构共同影响了风城组页岩油的微观赋存状态。 

Occurrence states and potential influencing factors of shale oil in the Permian Fengcheng Formation of Mahu Sag,Junggar Basin

Taking the Permian Fengcheng Formation of the Mahu Sag of the Junggar Basin as an example, a systematic study of shale oil was carried out for the occurrence states and potential influencing factors by integrating various data including cores, well logging, X-ray diffraction, argon ion polishing and field emission-scanning electron microscopy (FE-SEM) observations, high-pressure mercury injection (HPMI), rock pyrolysis, and two-dimensional nuclear magnetic resonance (NMR) experiments. The shale oil of the Fengcheng Formation in the Mahu Sag mainly has two modes of occurrence:film-like adsorbed oil and infilled free oil. The main constrains for shale oil occurrence state include lithofacies association, mineral composition and reservoir space. Four lithofacies associations namely dolomitic shale, sandy shale-dolomitic siltstone, dolomite rock containing alkaline mineral-argillaceous siltstone, and siliceous dolomite rock-dolomitic siltstone were recognized in the shale reservoirs of the Fengcheng Formation. The mineral composition, reservoir space, micro-pore structure and shale oil occurrence states of different lithofacies appeared to be quite different. The contents of quartz, pyrite and organic matter were positively correlated with thermal cracking hydrocarbon (S₂), and the contents of feldspar and dolomite showed a weak positive correlation with free hydrocarbon (S₁). The free oil was mainly stored in mesopores and large pores, such as secondary dissolution pores and residual intergranular pores. The absorbed oil was mainly stored in mesopores and small pores, such as organic pores, intercrystallite pores and the surface of mineral particles. The mineral composition and pore-throat structure were dominant factors controlling the occurrence state of shale oil.