复杂岩性沉积盆地油气演化的数学模型及其应用

MATHEMATICAL MODEL OF HYDROCARBON EVOLUTION IN SEDIMENTARY BASIN WITH COMPLEX LITHOLOGY AND ITS APPLICATION

对现有的油气演化数学模型进行了改进.并提出了复杂岩性地层剖面的回剥模型.利用这一模型.可以同时处理碎屑岩和碳酸盐岩两类剖面以及砂岩、泥岩、石灰岩、白云岩和膏盐五种岩类.把Falvey镜质体理论模型引入热史模拟中.从而使现在的热史模型可以在模拟热流史和地温史的同时.直接地模拟出烃源岩的R_0史.同时提出了组分产率曲线法这一新的生烃史模拟方法.它不仅可以模拟出烃源岩的生油史和生气史.而且还可以模拟出各烃类组分的生成史.利用这一组模型.可以对既有碳酸盐岩又有碎屑岩的复杂岩性沉积盆地中的油气演化进行模拟.该模型已成功地应用于鄂尔多斯地区古生界油气演化的模拟中.

The mathematical model of hydrocarbon evolution in this paper consists of a backstripping model of complex lithology section, a thermal evolution model and a hydrocarbon generation model. In the backstripping model, the stratigraphic section in a sedimentary basin is divided into clastic and carbonate. The clastic section consists of sandstone and mudstone, the lithological composition of which is represented by the mudstone content, and the carbonate section consists of limestone, dolmite and evaporites, the lithological composition of which is represented by the limestone and evaporite contents. The compaction feature of the above five kinds of rocks is represented by the porosity-depth relations. With this backstripping model, the burial history of a stratigraphic section with complex lithology can be modeled. In the thermal evolution model, the inversion method is used and vitrinite reflectance is used as the thermal indicator or fit the thermal history of a basin. The thermal evolution model here consists of four models: present heat flux model. paleoheat flux model, paleo-temperature model and vitrinite reflectance model. This thermal evolution model can simulate not only the heat flux and temperature histories, but also the vitrinite reflectance history of source rock directly without the help of TTI value. A new method of hydrocarbon modelling is developed in the paper, called components generation ratio curves method. It simulates hydrocarbon generation history on the basis of the generation ratio curves of hydrocarbon components derived from the thermal simulation of a particular source rock in laboratories. This method can give out the oil generation history and gas generation history of a source rock simultaneously, and further the generation histories of hydrocarbon components. With the above models, the oil and gas evolution history in a sedimentary basin with complex lithology can be modeled. The model has been successfully applied to the Paleozoic in the Ordos Basin.