Abstract:

In recent years, there are found much natural gas in the PaleogeneNeogene strata of Western Qaidam Basin, but the proved reserves of natural gas are far less than the natural gas resources. This needs to turn resources into reserves and enhance the basic geological research of the natural gas generation, migration and accumulation rules, in which the period of gas accumulation research is the most important. Therefore, in this paper, the PaleogeneNeogene strata of Western Qaidam Basin are selected as the main research object. Based on gathering many samples in Western Qaidam Basin and testing their homogenization temperatures, collecting and analyzing the homogenization temperatures of 22 fluid inclusions samples from different structural belts in Western Qaidam Basin, we have studied the period of PaleogeneNeogene gas accumulation with basin modeling and trap evolution to provide the basis for further natural gas exploration. The results show that the main hydrocarbon generation periods of PaleogeneNeogene source rocks are final N12N22 stage and final N32Q stage in Western Qaidam Basin; that the period of trap formation and development is throughout Paleogene and Neogene, and gas accumulation period is later than trap formation, considering after final N1 combined with hydrocarbon generation history; that the homogenization temperatures of fluid inclusions and the curves of geothermal history and burial history also confirmed that there were at least two times of oil and gas filling in the study area, namely final N1early N12 and final N22early N32. In a word, the characteristics of PaleogeneNeogene natural gas in Western Qaidam Basin are the multistage hydrocarbon generation and later accumulation; and the main periods of gas accumulation in the work area are final N1early N12 stage and final N22early N32 stage, with obvious long accumulation period and stage. Finally we put forward the proposal that exploration deployments should be proceeding around the final N1early N12 stage and final N22early N32 stage of middleshallow gas reservoir, in order to open a new scene for the exploration and development of natural gas in the study area.

Key words: Western Qaidam Basin, natural gas, basin modeling, trap evolution, homogenization temperature, period of accumulation