Middle And Lower Jurassic Source Rocks And Oil And Gas Formation In The Northern Qaidam Basin

This thesis takes the Middle and Lower Jurassic petroliferous systems in the northern Qaidam Basin as the research object.By analyzing the organic facies of the Middle and Lower Jurassic source rocks,and combining the logging data to quantitatively evaluate the source rocks,different organic facies sources are determined on the basis of thermal history calibration.Spatial distribution of rock hydrocarbon generation,based on the spatial distribution of source rocks and discovered oil and gas reservoirs,discusses the relationship between source rock kitchens and oil and gas reservoirs in the northern margin of the Qaidam Basin.Analysis of source rock data shows that F-facies source rocks are mainly developed in the lower Jurassic in front of the Altun Mountains in the northern margin of the Qaidam Basin,with a thickness of 10 m-80 m.The Lenghu Sag mainly develops D/E facies source rocks,mixed with some C and F facies,mainly sourced light oil,D/E facies source rock thickness is 20 m-350 m,C facies source rock thickness is 10 m-45 m,F facies source rock thickness is 10 m-260 m;Ma Hai,The Nanbaxian area mainly develops D/E facies source rocks,which are mainly condensed oil and gas,with a thickness of 50 m-350 m.The maturity of the Lower Jurassic source rock is 0.4-3.6%Ro,mostly in the mature,high-mature and over-mature stage,with a total oil discharge of 0.4-7.5 mmt/km~2 and a total discharge of 1-11 billion cubic meters/km~2.Among them,the displacement in front of Altun Mountain is 1-4.5 billion cubic meters/km~2,the average oil displacement in Lenghu Sag is 3.6 mmt/km~2,and the average displacement in Lenghu Sag is 7 billion cubic meters/km~2.The average oil displacement in Mahai and Nanbaxian is 3 mmt/km~2,and the displacement is 8 billion cubic meters/km~2.The Middle Jurassic source rock has a maturity of 0.2-1.9%Ro,and is mostly in the low-mature and mature stage.The total oil discharge of the Middle Jurassic source rock is 0.2-0.8 mmt/km~2,and the total gas discharge is 1-1.2 billion cubic meters/km~2.The comparison of oil and gas sources shows that the Niudong and Dongping gas reservoirs,the Lenghu oil and gas reservoirs,and the Mahai and Nanbaxian oil and gas reservoirs are mainly derived from the Lower Jurassic source rocks in the northern margin of the Qaidam Basin.The density of crude oil in the Nanbaxian condensate gas reservoir and the Mahai oil and gas reservoir gradually decreases to the shallow part,which is characterized by facies differentiation and accumulation.