Research On Oil Source Conditions And Hydrocarbon Accumulation Of Chaiwopu Depression,in Junggar Basin

The Permian reservoirs with rich oil and gas resources in Chaiwopu depression,which has a better exploration potential.The thesis use the theory of petroleum system and based on the subject of petroleum geology,geochemical,structural geology and reservoir geology,and analysed the source of oil-gas in different tectonic by comparing with oil in Chaiwopu depression and the source rock in Chaiwopu depression and its adjacent region.The hydrocarbon accumulation stages and times of hydrocarbon reservoirs in Chaiwopu depression have been investigated,through fluid inclusion microthermometry,petrography and biomarkers analysis.Based on the analysis of source rock and tectonic evolution history and reservoir characteristics,and found out the main control factors and established accumulation model of hydrocarbon.New research shows that,the source rock of P₂l with high organic matter abundance and good kerogen type that at mature stage,the hydrocarbon potential of source rock in the north are superior to those in other area.There are structural and lithologic and complex hydrocarbon reservoirs in chaiwopu depression.Two episodes of oil charging are identified in the central area at around Late Permian and Mid-Early Cretaceous to Oligocene,respectively.The hydrocarbon mainly originated from the source rock of P₂l and P₂h of central area,and migrated to overlying strata through fault and accumulated in the Permian strata.Normal oil and condensate oil in different well areas or different layers of the same well area were mixture distribution,with the migration of high maturity oil in central depression.Two episodes of oil charging are also identified in the northern area at around Mid-Early Jurassic to Early Cretaceous and Mid-Early Cretaceous to Mid-Late Cretaceous,respectively.The first oil mainly originated from the source rock of P₂l in central Chaiowopu depression and the second hydrocarbon came from the source rock of P₂l in the lower walls of nappe,those oils migrated to the upper plate of nappe by the fault zone and accumulated in the Permian strata.Reservoirs in upper strata was suffered of water washing and biodegradation and generated light oil or thickened oil or bitumen,reservoirs in deep strata be saved without damage.Three types of reservoir-forming models are summarized,self generation and self accumulation,lower generation and upper accumulation,new source to old reservoir,and the main influencing factors are distribution of effective source rocks,evolution history of tectonic and faults,traps and reservoir.