准噶尔盆地玛湖凹陷二叠系烃源岩三芳甾烷分布特征及油源对比

准噶尔盆地玛湖凹陷二叠系风城组、乌尔禾组和其他不同层系原油中普遍检测出三芳甾烷(TAS)和三芳甲藻甾烷系列。基于多口井的原油和14块代表性烃源岩样品的芳烃组分色谱-质谱资料，系统分析其TAS组成特征，并将其用于油源对比研究。结果表明：TAS分布特征可以有效区分准噶尔盆地玛湖凹陷二叠系风城组烃源岩和乌尔禾组烃源岩。风城组烃源岩中TAS具有C₂₆-20S含量低、C₂₇-20R含量高的分布特征，并且几乎不含有三芳甲藻甾烷；而乌尔禾组烃源岩中TAS具有相反的分布特征，即C₂₆-20S相对丰度较高，C₂₇-20R相对丰度较低，并且具有分布完整的三芳甲藻甾烷系列。玛湖凹陷不同层系原油TAS分布特征基本一致，主要表现为C₂₆-20S含量低，C₂₇-20R含量高，三芳甲藻甾烷含量低或者未检测出，与风城组烃源岩分布特征相似。应用C₂₆-20S/C₂₈-20S TAS与C₂₇-20R/C₂₈

The distribution of triaromatic steroids in Permian source rocks and implications for oil-source correlations in the Mahu Sag,Junggar Basin,NW China

Triaromatic steroids (TAS) are effective indicators for crude oil family classification and oil-source correlation. Based on analyses of gas chromatographymass spectrometry (GC-MS) for aromatic fractions of representative oil and source rock samples in the Mahu Sag, this paper systematically studies the TAS distribution characteristics. The results show that the distribution patterns of TAS have distinct differences, which can effectively distinguish Permian Fengcheng Formation（P₁f） and Wuerhe Formation （P₂w） source rocks in the study area. The relative contents of C₂₆20S TAS are lower, while those of C27-20R TAS are relatively higher in the P1f source rocks. In contrast, the P₂w source rocks are characterized by high relative contents of C₂₆20S TAS and low relative contents of C₂₇20R TAS. Furthermore， the distributions of triaromatic dinosteranes in P₂w source rocks are complete and readily identified, while the P₁f source rocks contain less those compounds. All oil samples from different strata are characterized by low relative contents of C₂₆20S TAS， high relative contents of C₂₇20R TAS and less triaromatic dinosteranes, which is consistent with those of the P₁f source rocks. Low C₂₆-20S/C₂₈-20S TAS ratios， high C₂₇-20R/C₂₈-20R TAS ratios and the triangle diagram of C₂₆-C₂₈ TAS indicate that the crude oils in different strata are mainly derived from P₁f source rocks. Therefore, TAS and triaromatic dinosteranes can be used as effective molecular markers for oil source correlation in the study area.