扬子及周缘地区上奥陶统-下志留统烃源岩发育环境及其控制因素

扬子地区下古生界发育了上奥陶统五峰组和下志留统龙马溪组两套有效烃源岩,查清其发育环境及其控制因素具有重要的科学理论和油气勘探意义.晚奥陶世开始,扬子地区进入碎屑岩陆棚演化阶段;五峰期-龙马溪期,扬子地区主体为局限的深水陆棚环境,总体呈现出浅水陆棚、深水陆棚、次深海共存的古地理格局.沉积体系展布和沉积演化主要受扬子陆块与华夏陆块的汇聚作用控制.扬子地区上奥陶统-下志留统烃源岩的形成与生烃母质生物的高生产力和高埋藏率、冰期-冰后期之交的气温快速转暖、海平面快速上升以及粘土矿物在有机质富集保存过程中的赋存驻留作用等密切相关.

Sedimentary Environment and Development Controls of the Hydrocarbon Sources Beds: the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in the Yangtze Area

The hydrocarbon source beds of the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation were deposited in the Yangtze area.It is important in theory and practice to probe the mechanism of the development of marine hydrocarbon source beds,i.e.the precondition of breakthrough in the exploration of the marine strata in South China.From the Late Ordovician epoch,the Yangtze area began clastic shelf evolutionary phase.In Wufeng and Longmaxi age of the Late Ordovician and Early Silurian,the study area was mainly a restricted deep shelf.The paleogeographic framework was formed by the coexistence of shallow and deep shelves and bathyal environment.The distribution of sedimentary systems and sedimentary evolution were controlled by convergent squeezing of the Yangtze and Cathaysian platforms.The organic-rich source beds of the Upper Ordovician and the Lower Silurian in the Yangtze area are intimately related to these factors as following:the high organism production and bury,the rapid rise of sea level caused by a rapid increase of temperatures and melting of glaciers,between a glacial age and a postglacial age,enrichment of phosphorus element and the adsorption of clay minerals during the preservation of organic matter.