陆东凹陷低熟油特征及形成条件分析

CHARACTERISTICS AND FORMATION CONDITIONS OF LOW-MATURE OIL IN LUDONG SAG

陆东凹陷白里系所产原油多为低熟油。其特征为低合硫、中含蜡、凝固点中等、粘度中等、密度偏高；他和烃含量低、饱／芳值低、芳烃和非烃含量偏高。饱和烃色谱特征、生物标记化合物特征和稳定碳同位素组成特征均表明，菌藻类低等生物是重要的成烃母质。这些低熟油具有特定的形成条件：其烃源岩形成于微咸一半成水湖相强还原一还原环境，有机质丰度高且类型封，地热梯度较低，成烃门限深度之上有相当厚的烃源岩分布。

Most oils from Cretaceous reservoirs in Ludong sag are found to be low-mature ones, which are characterized by low sulphur and middle wax contents, middle pour point, middle viscosity, higher density, low saturated hydrocarbon content, low saturate hydrocarbon /aromatic hydrocarbon value and higher aromatic hydrocarbon and nonhydrocarbon contents. The characteristics of low-mature oils are studied by means of analyzing the physical properties, bulk compositions,chromatography of saturated hydrocarbon, biomarker fingerprints and stable carbon isotope compositions of them and so on.Their formation conditions are discussed in this paper based on the analyses on the geothermal distribution, hydrocarbon generating environment of source rock, generative organic matter and the model of hydrocarbon generation in Ludong sag.