STUDY OF THE PHYSICAL AND CHEMICAL CHARACTERISTICS OF THE CRUDE OIL AND OIL-SOURCE CORRELATION IN THE YANQI BASIN

At present,there are different opinions on the oil sources of the Jurassic net pay in Yanqi Basin,where crude oil has been found in Sangonghe Formation and Badaowan Formation.Through a series of researches on the physical and chemical characteristics of the crude oil in the study area,some differences between the oils in the two Formations have been found not only on the physical properties but also on the geochemical composition and biomarkers.Therefore,the crude oils in the area are considered to have different oil sources.The crude oil in Sangonghe Formation is attributed to typical humic kerogen origin.Besides having the same characteristics with the crude oil in Sangonghe Formation,the crude oil in Badaowan Formation comes from lacustrine mudstone.The further correlation analysis on the crude oil and various biomarkers shows that the crude oil in the Jurassic Sangonghe Formation differs greatly from the source rocks in Xishanyao Formation,Sangonghe Formation,Carboniferous and Triassic on geochemical characteristics,but is correlative with the source rock in Badaowan Formation.It is concluded that the curde oil in Badaowan Formation has good similarity with the source rock in Badao-wan Formation and the Triassic.Up to now,the exploration has been focused on the source rock in(Badaowan)Formation which is believed to be the main source rock.The favorable zones in the Triassic,which is thought to be a secondary source rock,should be paid more attention in next exploration deployment.