GEOCHEMICAL CHARACTERISTICS OF THE CRUDE OIL IN THE LUXI SAG, THE KAILU BASIN

The Luxi Sag is the area which has the highest exploration degree and the most oil and gas discoveries among the peripheral basins of Liaohe Basin.The crude oil maturity,the organic matter input and the depositional environment of Bao 1 Block and Bao 14 Block in the Luxi Sag have been studied based on the precise geochemical analysises of the crude oil samples.Many similar geochemical characteristics between the crude oils from Bao 1 Block and Bao 14 Block have been found,in Cluding:the Pr/Ph ratio is less than 0.6;the regular sterane distribution is dominated by C₂₉-steranes;the tricy Clic/pentacy Clic terpane ratio is less than 0.15,with the content of tricy Clic terpane being obviously less than pentacy Clic terpane;the base peak of the tricy Clic terpane is C₂₃ and that of the pentacy Clic terpanes is C₃₀,with the Ts/Tm ratio ranging from 0.7 to 1.0 and certain amount of gamacerene.But some differences between the two blocks also exist.Bao 14 Block has a slightly higher maturity,the base peak of n-alkanes in Bao 1 Block is mostly characterized by C₂₀,and that in Bao 14 Block is mostly characterized by C₂₁;the ratio of C_15-21/C_22-28 in Bao 1 Block is higher than that in Bao 14 Block;and Bao 1 Block has higher gamacerene index,indicating that Bao 1 Block was deposited under a higher salinity environment.The hopane/sterane ratio in Bao 1 Block is lower,suggesting that the algae were rather developed and the higher salinity environment may suppress the bateria.