生油古湖泊生产力的估算方法及应用实例

文中综述了生油古湖泊生产力估算的常用方法,并以山东东营凹陷早第三纪生油湖为例进行了应用尝试。结果表明,无论是定性分析还是定量计算,均以沙三中、下亚段、沙四上亚段和沙一段沉积时期的古湖泊生产力最高,其次是沙三上亚段沉积时期,沙二段沉积时期古生产力最低。把东营湖古生产力定量计算的结果与现代不同营养类型湖泊生产力的值相比较,可以发现沙三中、下亚段、沙四上亚段和沙一段沉积时期的东营湖是超养湖,沙三上亚段沉积时期是富养湖,沙二段沉积时期是中养湖。所以沙三中、下亚段、沙四上亚段和沙一段沉积时期古湖泊最有利于生成石油,这与油气勘探的实际结果极为吻合。

Estimation Method on Productivity of Oil-producing Lake and a Case Study

Commonly used methods on evaluating the productivity of oil-producing lake have been reviewed and take the Paleogene Lake (refered to as Dongying Lake) in the Dongying depression, Shandong Province, as a case study. These methods include organic carbon analysis, paleontological analysis and stable carbon isotopic analysis. The Paleogene sediment of the Dongying depression mainly composed by the Dongying Formation (Oligocene) and the Shahejie Formation (Eocene-Oligocene).These formations can be subdivided into some members, for example, the Shahejie Formatin is divided into four members including first member(SHA1), second member(SHA2), third member(SHA3) and forth member(SHA4). Both qualitative and quantitative methods show that the level of productivity in the lower-middle SHA 3, upper SHA 4 and SHA 1 are the highest, the second is the upper SHA 3, and the level of productivity in SHA 2 is the lowest. Compared with the productivity of different modern lakes, we concluded that the lake in lower-middle SHA 3, upper SHA 4 and SHA 1 depositional period are hypertropic lake and these lake are the most favorable for the formation of lacustrine oil. The lake in the upper SHA 3 is eutrophic lake and in SHA 2 is Mesotropic Lake. These lakes have poor potential for the formation of lacustrine oil.