羌塘盆地是青藏高原北部的大型海相含油气盆地，研究区塞仁地区位于南羌塘坳陷，该区油气地球化学研究成果较少、研究程度较低。对古油藏含油层样品的族组成及甾萜烷等地球化学特征进行总结，并结合多种生标参数得出结论。该地区古油藏整体处于低成熟-成熟阶段，C₂₇甾烷较C₂₉甾烷占优势，并且三环萜烷类化合物以C₂₃三环萜烷为主峰，也表明母质来源以海相有机质为主，并有一定的陆源有机质贡献。油藏样品具有较低的姥植比（Pr/Ph < 1），非藿烷中检测出一定丰度的伽马蜡烷以及较高的C₃₅/C₃₄升藿烷值特征，这些参数指示古油藏形成于沉积水体较深、还原性相对较强并具有一定盐度的沉积环境。该地区古油藏地球化学特征分析为油气成藏研究与油气富集规律认识奠定了基础，确定了该地区古油藏的沉积环境和母质来源。古油藏母质来源以海相为主，沉积环境为较还原环境。

The Sairen region, situated in the Qiangtang Basin, a large marine oil and gas basin in the northern part of the Qinghai-Tibet Plateau, is located in the southern Qiangtang Depression. This area has seen limited research and a relatively low level of understanding in the field of oil and gas geochemistry. The group composition and the geochemical characteristics of steroidal terpenes in oil reservoir samples were summarized, and a conclusion was drawn by integrating various biomarker parameters. The paleo-reservoir in this region, as a whole, are in a stage ranging from low to mature maturity. C₂₇ steranes predominate over C₂₉ steranes, and tricyclic terpanes, with C₂₃ as the main peak, indicate a predominant marine organic matter source with some contribution from terrestrial organic matter. The reservoir samples exhibit a low pristane/phytane ratio (Pr/Ph < 1). In non-hydrocarbon compounds, gammacerane is detected in certain abundance, along with a relatively high C₃₅/C₃₄ hopane ratio, suggesting that the paleo-reservoir formed in a sedimentary environment with relatively deep deposition, strong reducing conditions, and a certain salinity. The geochemical analysis of paleo-reservoir in this region lays the foundation for the study of hydrocarbon accumulation and understanding the laws of oil and gas enrichment. It establishes the sedimentary environment and organic matter source of paleo-reservoir in this area, with a predominant marine organic matter source and a sedimentary environment characterized as relatively reducing.