下古生界高过成熟烃源岩成熟度指标--姥鲛烷异构化指数研究

Study on Pristane Isomerization Index,a Possible Thermal Maturity Index for Highly and Overly Mature Source Rocks of the Lower Paleozoic

采用GC/MS方法对准噶尔盆地高过成熟煤岩中的姥鲛烷非对映异构体进行分离与分析,并对其异构化指数与镜质体反射率的相关性进行研究。结果表明,姥鲛烷非对映异构体的异构化指数与镜质体反射率有着良好的线性关系,拟合优度r2为0.995 1。应用四川盆地高过成熟烃源岩进行验证,其点的分布均在相关区域范围内,偏差较小,拟合优度r2达到了0.897 9。因此,姥鲛烷非对映异构体的异构化指数可作为判识有机质高过成熟度的新指标,可为高过成熟烃源岩热成熟度判识的研究提供新途径。

The separation and analysis of the diastereoisomers of pristine （2,6,10,14-tetra- methylpentadecane） in these highly and overly mature coal samples from the Junggar Basin were carried out by gas chromatography mass spectrometry （~GC/MS）, and the relativity of the pristane isomerization ratio （PIR） and the reflectances （Ro） of these coal samples were studied. The results show that the PIR keeps quite linear relation with the Ro, and the linearity is up to 0. 995 1. Furthermore, verified test with source rocks of the Sichuan Basin was conducted in laboratory scale. It has been proved by experiments that the model has a precision of 0. 897 9 in forecasting the test results. The results suggest that the PIR may be used as an new indicator of maturity for the highly and overly mature source rocks, and it provided a new way to identify the maturity of these highly and overly mature source rocks.