准噶尔盆地腹部及西北缘斜坡区原油成因分析

ANALYSIS OF CRUDE ORIGIN IN HINTERLAND AND SLOPE OF NORTHWESTERN MARGIN, JUNGGAR BASIN.

三环二萜烷内分布是反映原油母质来源的一个良好指标。根据三环二萜烷的内分布，把准噶尔盆地腹部及西北缘斜坡区的原油划分为四种基本类型。第一类，Ｃ２０、Ｃ２１和Ｃ２３三环二萜烷呈上升型分布，主要来源于风城组烃源岩；第二类，Ｃ２０、Ｃ２１和Ｃ２３三环二萜烷以Ｃ２１为主峰呈“∧”型分布，主要与中二叠统烃源岩有关；第三类，以Ｃ２０为主峰，Ｃ２１和Ｃ２３基本相等或依次降低的下降型分布，推测与佳木河组关系较密切；第四类，在三环二萜烷含量较低的背景上Ｃ１９、Ｃ２０三环二萜烷和Ｃ２４四环二萜烷含量显著，这是侏罗系煤成油的典型特征。三环二萜烷内分布不同的原油在其他地化指标上也有差异，因而它不是一个孤立的指标，而是各种指标的突出表征。通过分析认为。

Tricyclic diterpane internal distribution is an excellent indicator for source of crude oil. In hinterland and slope of northwestern margin of Junggar basin, crude oil is then divided into four basic types. In Ⅰ type oil, C20, C21 and C23 tricyclic diterpane have an ascending distribution, which mainly originate from Fengcheng formation. In Ⅱ type oil, C20,C21 and C23 tricyclic diterpane have an inverted “V' distribution with C21 as the main peak, which are associated with Middle Permian. In Ⅲ type oil, C20 is the main peak, while C21 and C23 approximate or distribute in a descending order, which are possibly related with Jiamuhe formation. In Ⅳ type oil, tricyclic diterpane is relatively low but C19,C20 tricyclic diterpane and C24 tetracyclic diterpane have higher content, which is typical for Jurassic coal formed oil. The oil with different tricyclic diterpane internal distribution is different in other geochemical indexes. Analysis showed that multi source, multi period reservoir formation with superimposition is a common feature for the known reservoirs in hinterland and slope of northwestern margin in Junggar basin.