梅河盆地古近系梅河组煤与油页岩有机质差异富集与共生机理

As two types of important organic-rich energy resources, oil and Coal not only have obvious enrichment difference on organic matter,but also develop in the same mine. However, previous studies have not investigated their organic enrichment difference and co-enrichment mechanism. In order to document the formation of oilshale and coal and their related rules of spatial-temporal distribution，this study focuses on the Paleogene Meihe Formation in Meihe Basin (NE China), in which the oil shale and coal beds are interbeded or occur as contacting thick layers.Aiming at coal and oil shale with high content of organic matter, this study will use sedimentary organic facies to discuss the organic enrichment difference between coal and oil shale.By sequence stratigraphy combined with sedimentary organic facies, this paper will also show variation of sedimentary organic facies in the high-resolution sequence stratigraphy model in different sequence classification from subsequence, system tract and sequence. Co-enrichment mechanism of Coal and Oil shale of the Paleogene Meihe Formation will be revealed in the isochronous sequence stratigraphic framework eventually. This study will be an important contribution for understanding the formation of coal and oil shale, and also for the exploration of large oil shale/coal deposits, shale gas and coal-bed methane. Meanwhile,those results will further perfect the sedimentary organic facies method applying in continental rift basin.

油页岩与煤是两种重要的有机质极为丰富的有机能源矿产，两者不仅存在明显的有机质富集差异，还常同时出现，却很少有人讨论其有机质富集差异和共生机理。本次选择具有油页岩与煤频繁互层、较厚油页岩直接沉积在较厚煤层之上赋存特征的梅河盆地为靶区，以古近系梅河组含油页岩、煤系为目的层，开展煤与油页岩沉积环境、沉积有机相、高分辨率层序地层等研究。针对煤与油页岩中有机质丰富，利用沉积有机相分析方法，弄清楚煤与油页岩的有机质差异富集机理。采用层序地层学与沉积有机相的结合，弄清楚从准层序、体系域到层序不同级别的沉积有机相的分布特征，最终在统一的等时层序格架内揭示油页岩与煤的共生机理。通过本次研究，将对于进一步完善煤、油页岩成矿理论，科学预测大型油页岩、煤矿床以及页岩气、煤层气等多种资源矿产具有一定的科学和理论意义。同时，将进一步的完善基于层序的沉积有机相方法在陆相断陷盆地的应用分析。

项目选择具有油页岩与煤频繁互层、较厚油页岩直接沉积在较厚煤层之上赋存特征的梅河盆地为靶区，通过开展古近系梅河组含油页岩、煤系研究，在垂向上揭示了有机质富集规律以及油页岩与煤的共生成因。. 项目通过开展野外露头、室内岩心观察，对连续取心关键井开展高密度、连续的煤岩和煤质特征、油页岩品质和有机显微组分、有机地球化学特征等分析，揭示了研究区油页岩赋存规律及成因。单独发育的煤主要发育在扇三角洲河道间沼泽，单独发育的油页岩形成于半深湖—深湖环境，而共生的油页岩与煤主要形成于浅湖-沼泽沉积环境。在初始沉降阶段中期和盆地萎缩阶段初期，在稳定浅水地带，较少的陆源供给兼具较好的保存条件和高等植物大量繁殖，易于形成煤层沉积; 而在盆地最大沉降阶段，稳定深水区域，伴随着较高的湖泊生产力和良好的保存条件，形成油页岩沉积。 含煤-油页岩段煤形成于梅河组上含煤段盆地萎缩阶段，主要为一套扇三角洲前缘-浅湖-沼泽沉积环境，含煤、油页岩岩系中不同的沉积-成矿序列主要形成于与沼泽有密切成因联系的浅湖环境，主控因素是浅湖时期的湖平面或沼泽时期的潜水面。盆地的充填的末期，由于陆源碎屑相对供给较少，在局部地区，水生等低等生物大量繁殖，并且该时期的湖泊水动力条件也很弱，湖泊中的氧气很快就因氧化前期沉积的有机物而消耗完了，形成了良好的还原环境，容易形成有机质为I型的油页岩。但由于处于盆地充填末期，该湖相环境的油页岩分布并不稳定，通常很薄，很快随着盆地充填末期湖平面的下降，迅速沼泽化，形成煤沉积。因此，在梅河组上含煤段的研究层位自下而上发育了煤-油页岩以及油页岩-煤-油页岩的组合特征。