大民屯凹陷沙四段页岩含油率影响因素分析

Analysis of Influence Factors for Shale Oil Contents in 4^(th) Member of Shahejie Formation in Damintun Sag

随着大民屯凹陷沙四段页岩取得页岩油突破,该地区成为页岩油研究的热点,对沙四段页岩含油率影响因素进行分析有助于页岩油聚集条件和分布规律的探索。在岩心实验测试的基础上,分析了沙四段页岩的地球化学、储层和含油性等特征。通过微量元素对古环境的表征,提出"温润—闭塞—湖侵"的古环境模式是沙四段富有机质页岩形成的重要条件,温润的气候、闭塞的沉积环境和上涨的水体分别对有机质的生成、聚集和保存起到促进作用。利用热解法得到含油率,结果表明沙四段页岩含油性很好,含油率在0.08%~0.99%之间,平均值为0.43%。研究认为页岩含油率受生烃条件、储集条件和保存条件的影响,高有机质丰度、适中的高成熟度、高脆性矿物含量、优质的顶底板和地层超压是沙四段页岩油富集并具备高含油率的有利因素。

As the 4th Member of Shahejie Formation(E_2s_4) shale in Damintun sag has got breakthrough in shale oil, this region has become the study hotspotfor shale oil.To analyze the influence factors for shale oil contents in E_2s_4 in Damintun sag is helpful forexploring accumulation conditions and distribution regularity of shale oil. On the base of core experiments, we analyzed geochemical, reservoir and oil content characteristics of E_2s_4 shale. By characterizing the ancient environment using trace elements, we proposed that the 'warm and moist-occlusivelacustrine transgressive' ancient environment model was important condition forforming organic-rich shalein E2s4. Warm and moistclimate, occlusive deposit environment and rising water level promoted organic matter generation, accumulation preservation, respectively. By utilizing Rock-Eval method, we got shale oil contents. The results show that E_2s_4 shalehas high oil contents(0.08%-0.99%, average 0.43%). According to our studies, shale oil contents are influenced by hydrocarbon generation condition, reservoir condition and preservation condition. High organic matter abundance, appropriate high maturity, high brittleness mineral content, high quality of roof and floor, and formation overpressure are favorable conditions for shale oil enrichment and high oil contents.