Maturity effects on steranes of source rocks in Lishu fault depression,Songliao Basin

作者：Chuanjun Yi,Min Zhang,Li Teng

摘要：Geochemical analysis results of 30 source rock samples from Lishu fault depression in Songliao Basin show that samples are compositionally similar and represent a uniform organic facies.Differential distribution of steranes among the samples is due to rank,with vitrinite reflectances(Ro)ranging from 0.65 to 1.61%.In the maturity stage(Ro=0.65-1.20%),the absolute concentrations of steranes increase,which is affected by kerogen degradation,whereas the pyrolysis of high mature source(Ro=1.20-1.61%)show a decrease in the abundance of steranes.Simultaneously,the parameters of steranes vary greatly with maturity.Decrease of prognane/regular sterane value with the increase of maturity suggests that pregnane is not a product of regular steranes pyrolysis.The ratios of C27/C29regular sterane gradually increase,while the value of C29-20S/(20S+20R)and αββ/(αββ+ααα)decrease at high maturity stage,which is associated with the difference in the thermostability of steranes involved.This reversed trend can be used to determine the high-maturity stage of source rocks.Whereas the values of rearranged steranes/regular steranes in source rocks show an apparent positive correlation with maturity,it,therefore,appears to be particularly useful for maturity assessment at elevated levels.

发文机构：College of Resources and Environment Key Laboratory of Exploration Technology for Oil and Gas Resource

关键词：ThermaleffectSTERANESGeneticmechanismLacustrinesourcerocksMATURITY

分类号： P61[天文地球—矿床学]