华北地台早二叠世太原组和山西组煤沉积模式与生烃关系研究

中华北地台区部（鲁西）、中部（晋中）和鄂尔多斯盆地，二叠系太原组煤系形成于海侵体系域成煤环境，山西组煤系则主要形成于陆相高位体系域的三角洲成煤环境。这两种环境下形成的煤在硫含量及其赋存形态、有机显微组分组成等地球化学特征方面存大较大差异：太原组煤中总硫含量比山西组煤高，太原组煤中硫的赋存形态以黄铁矿为主，山西组煤以硫酸盐硫为主。有机显微组分中，太原组煤的镜质组平均含量高，且以基质镜质体为主，惰性组平均含量低，山西组煤 的镜质组平均含量相对低，且其中的基质镜质体平均含量远低于太原组，惰性组平均含量却比太原组煤高。太原组煤的凝胶化指数较大，而植物结构保存指数值较小；山西组煤则凝胶化脂数值较小而植物结构保存指数值较大。从煤成烃角度出发，太原组煤系优于山西组，太原组煤系应是华北地台最有利的生烃层系。图3表3参14

Relationship between coal depositional modes and hydrocarbon generation of the Early Permian Taiyuan and Shanxi Formation in Huabei Platform

In the eastern and central parts of North China Platform and Ordos Basin, the coal series in Taiyuan Formation are formed in a coal depositional environment of a transgressive system tract while those in Shanxi Formation is deposited mainly in a terrestrial delta coal-forming environment of a highstand system tract. Coals formed in the two depositional environments are quite different in organic-geochemical features, such as sulfur content, sulfur molecular configurations and macerals. Sulfur is more abundant in Taiyuan Formation than in Shanxi Formation. In Taiyuan Formation, sulfur is mainly in the form of pyrite sulfur, while in Shanxi Formation sulfur is chiefly in the form of sulfate. The coal macerals in the Taiyuan Formation are of high average vitrinite content, mainly desmocollinite, and low average inertinite content, while that in the Shanxi Foramtion are of lower average vitrinite content and much lower desmocollinite content, but of higher inertinite content. The Taiyuan Formation coal is high in GI (Gelification Index) but low in TPI (Texture Preservation Index), while the Shanxi Formation coal is lower in GI but higher in TPI. The transgressive Taiyuan Formation coal series should be the best hydrocarbon-generating deposit in the studied area.