鄂尔多斯盆地延长组湖相页岩油赋存状态评价与定量表征

Occurrence states and quantitative characterization of lacustrine shale oil from Yanchang Formation in Ordos Basin

鄂尔多斯盆地长7段源内夹层型页岩油已取得勘探突破并实现规模效益开发,但泥页岩层系是否具有勘探潜力,页理型页岩油的烃类赋存状态与表征方法仍然不够明确。通过对比页岩层产出的页岩油与滞留烃性质发现,鄂尔多斯盆地延长组长7页岩层产出的页岩油具有中轻质烃类组分(nC_(25-))显著优势、沥青质组分很低的特征,属于轻质油,而滞留烃中大分子化合物含量较高。各项分析测试与试验研究表明,油质组分与沥青质相容性差,两者赋存状态差异明显,沥青质组分主要被干酪根所吸附,油质组分主要以游离态赋存于孔裂隙中。长7段富有机质泥页岩中较高的沥青质含量不会明显影响页岩油的可流动性。同时建立的“泥页岩中分离提取游离烃的方法”,可作为页岩含油性快速评价的实用技术,定量表征结果表明长7泥页岩中游离烃含量较高,平均在5 mg/g左右,页理型页岩油勘探潜力很大。

The exploration breakthrough of Chang 7 Member shale oil from sandstones in Ordos Basin has been made and scale effect has been realized,however,whether the mudstone and shale series have exploration potential and how to characterize the hydrocarbon occurrence states are still questions.Contrast between the shale oil and residual hydrocarbons shows that the test shale oil has high content of light and medium hydrocarbons(nC25-)but very low abundance of asphaltene,while the retained hydrocarbons has high concentrations of macromolecular compounds.Analytical tests and experimental studies suggest that the oily components have poor compatibility with asphaltene,their occurrence stats are distinct,the asphaltene components are mainly adsorbed by kerogen while the oily constituents occur in the pores and fractures as free hydrocarbons.Therefore,high contents of asphaltene will not affect the mobility of shale oil.Moreover,the method of separating and extracting free hydrocarbons from shale and mudstones is not only a rapid technique for shale oil resources evaluation,but also reveals that the free hydrocarbon contents of Chang 7 Member shale and mudstones are very high with an average content of 5 mg/g,showing a significant potential of shale oil exploration from mud shales.