论文部分内容阅读
上奥陶统—下志留统烃源岩是中国南方海相4套主力区域烃源岩之一,有关它形成与发育环境的研究是南方海相油气成藏理论的基础性问题。本文选择中上扬子南缘2条代表性剖面,对上奥陶统—下志留统沉积岩进行了详细的地球化学分析,提取其中对沉积古环境有指示意义的地化指标,对该段地层的古环境进行了恢复。研究表明,优质烃源岩段主要集中在上奥陶统五峰组和下志留统龙马溪组底部,V/(V+Ni)、Ni/Co、Ceanom、δEu和δ13Corg等地球化学指标与有机碳含量均有较好的相关性,这些指标的异常均表明优质烃源岩发育于缺氧环境。而龙马溪组上部地层的有机碳含量较低,各种地球化学指标也显示,此时缺氧环境遭到了破坏,这与当时的沉积环境多为高能环境、不利于烃源岩发育是一致的。
The Upper Ordovician-Lower Silurian source rock is one of the four main source rocks in the marine facies of southern China. The study of its formation and developmental environment is the basic issue of the hydrocarbon accumulation in the southern marine. In this paper, two representative sections of the southern margin of Middle Upper Yangtze are selected to conduct a detailed geochemical analysis of the Upper Ordovician-Lower Silurian sedimentary rocks and to extract the geochemical indicators which are indicative of the sedimentary paleoenvironment. The ancient environment was restored. The results show that the source rocks of high quality are mainly concentrated in the bottom of the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation, and the geochemical indexes of V / (V + Ni), Ni / Co, Ceanom, δEu and δ13Corg are similar to those of organic Carbon content have a good correlation, the abnormalities of these indicators indicate that high-quality source rocks developed in anoxic environments. However, the organic carbon content in the upper strata of the Longmaxi Formation is relatively low, and various geochemical indicators also show that the anoxic environment was destroyed at this time. This is not consistent with the fact that the depositional environment at that time was mostly a high-energy environment, which hindered the development of source rocks .