Study On The Petroleum Migration Law Of The Upper Cretaceous In The West Slope Of Songliao Basin

The oil and gas fields discovered in the west slope area include Fulaerji oil field,Pingyang oil and gas field,Erzhan gas field,Jiangqiao oil field,Alaxin gas field and Baiyinuole gas field.Except for the Fulaerji Oilfield and Pingyang Oilfield,most of the remaining oil and gas fields are distributed in the Taikang uplift zone.As the oil and gas distribution range in the western slope area away from the source area becomes narrower and narrower,the beads are distributed on the plane,indicating that there may be The advantageous migration path of oil and gas.In this paper,the comprehensive analysis of source rock geochemical characteristics,crude oil biomarker compound characteristics and migration characteristics to explore the oil and gas migration laws of the Upper Cretaceous in the west slope area can provide a scientific basis for oil and gas exploration.Combining pyrolysis chromatography,TOC testing and source rock Ro analysis,it is concluded that the most favorable source rock in the western slope of the Songliao Basin is the mudstone of the first member of the Qingshankou Formation in the Qijiagulong Depression,due to its higher organic matter content,hydrocarbon expulsion rate and The type of stable organic matter is obviously superior to that of the second and third section of the Qingshankou Formation and the 1st section of the Nenjiang Formation.The organic matter abundance of the source rocks of the second and third sections of the Qingshankou Formation in the Qijiagulong Depression are all below 6%.The type of organic matter is mainly type?_?.The second and third sections of the Qingshankou Formation has reached the threshold of hydrocarbon expulsion depth,which can be regarded as effective source rock.Although the source rocks of the Nen1 in the sag area have the highest organic matter abundance,they have not reached the threshold depth of hydrocarbon expulsion and cannot supply hydrocarbons to the Cretaceous oil layer on the western slope.The sand bodies in the second and third sections of Yaojia Formation have a wide distribution range and a large thickness,with the overlying mudstones of the first section of Nenjiang Formation are a good regional cover layer.Conglomerate,unconformity and sand body together constitute the main channel for the lateral migration of oil and gas.A large number of NE faults developed in the southeast of the west slope,connected the source rocks and main reservoirs of the Qing 1 section,and became the main channel for the vertical migration of oil and gas.The oil source comparison results show that the mudstone of the first member of the Qingshankou Formation in the Qijiagulong Sag is the main source rock of crude oil in the west slope region.The difference in crude oil maturity is controlled by the hydrocarbon expulsion period and also contributes to a small amount of low mature oil produced by the source rock in the slope region Relevant,the water environment and organic matter sources of the Qingshankou Formation and Nenjiang Formation during mudstone deposition are relatively stable.The paleofluid potential recovery results show that the location of the high potential area is basically the same as the location of the main source rocks of the sag,and the hydrocarbon expulsion centers are generally located.Therefore,the oil and gas generated by the hydrocarbon generation centers are generally toward the edge of the depression and other areas(Longhupao terrace and Taikang Uplift belt)for large-scale migration,most westward migration to the western overburden.In the context of the overall migration area,the distribution of fluid potential in different target layers is not exactly the same.However,both indicate two migration paths,namely the central and northwestern Qijia Depression-Taikang uplift belt;the southern and southwestern Gulong Depression-Taikang uplift belt.