Abstract:

Ordos Basin is the second largest sedimentary basins, with abundant Mesozoic crude oil resources. Longdong area is located in southwestern Ordos Basin. The Chang 3 oil group of Jurassic Yanchang Formation is an important oil-bearing layer. Based on the characteristics of crude oil and oil-source analysis of the conditions for Chang 3 oil group. Making use of the composition of the nitrogen compounds in crude oil and the changes of the absolute concentration, combining with the research results of the comparison of source rock and oil source correlation, this paper discuses the migration characters and directions of Chang 3 oil group in the Longdong region of Ordos Basin. The results show that in the distribution and composition of nitrogen compounds in crude oil from vertical and longitudinal, there are evident migration and fractionation effects which can be used to indicate the regional migration of crude oil better. From Late Jurassic to Early Cretaceous,Chang 7 high-quality source rock had reached generation thresholds. At the same time, there are plenty of hydrocarbons generation which have an lateral migratory extend from the centers of the basin and hydrocarbon generation to the west, the southwest and the northwest,in ways of verticality, laterality and alternation of them.

Key words: Chang 3, nitrogen compound, hydrocarbon migration, Ordos Basin