The Immature Oils in Santanghu Basin

Key words: 
• Santanghu Basin /
• Lucaogou Formation /
• immature oii /
• macerai /
• sapropeiic amorphous

Abstract: Most of the oiis found in Santanghu basin were regards as immature, mainiy because the vaiues of 20S/（20S + 20R）of C₂₉ sterane are iower than 0.42. Compared with other immature oiis reported in china, they have some speciai characteristics.Through anaiyzes to oii source, these immature oiis mainiy come from Lucaogou Formation of upper Permian which is better source rocks with iow maturity and much abundance of organic matter. Different from other immature source rocks in Santang iake basin, Lucaogou formation abounds with sapropeiic amorphous that content abundant hydrogen. It can be iearned through pyroiysis that the sapropeiic amorphous is the main contributor of hydrocarbon in Lucaogou formation and the Ro of its main hydrocarbon-generating intervai is from 0.35% to 0.6%, which is the main hydrocarbon-generating mechanism of the immature oiis in Santang iake basin. Furthermore, The series of 17α（H）- 25 - norhopane compound was found not oniy in oii, but aiso in Lucaogou formation, which hints that the immature oiis in Santang iake basin may have reiations with the bacteria degradation of terrigenous organic matter.