Abstract The Tuofutai Bulge in the Tabei Uplift of Tarim Basin, western China, has become a hot spot for petroleum exploration in recent years. Fifteen Ordovician oil samples from 15 wells in the Tuofutai Bulge were analyzed for biomarkers and carbon isotopes using gas chromatography–mass spectrometry and stable carbon isotope analysis to constrain its depositional environment, thermal maturity, source rocks and the possible petroleum charging directions. The samples were characterized by abundant terpenoids, relatively high contents of C29 regular steranes and dibenzothiophene, relatively low ratios for Pr/Ph and C22/C21 tricyclic terpanes, and high ratios of C35/C34 homohopanes. Results suggest that the source rocks for the oils were deposited in a reducing marine carbonate and marl environment. Cambrian and Ordovician source rocks contribute to the oils, and the Middle to Upper Ordovician source rocks exert a greater contribution. n-alkanes and abundant 25-norhopanes in the saturated fractions suggest that the oil is a mixture of early biodegraded oil and late normal crude oil charged at later time. Data from methyldiamantane parameters suggest that the crude oil is in a high maturity stage. The tracing of oil charging suggests that preferential migration directions are primarily from south to north, connected with oil migration along the Shenbei No.1 Fault from the Shuntuoguole Lower Uplift to the south of Tabei Uplift.

中文翻译：

---

塔里木盆地北部托弗台凸起奥陶系石油的分子标记和碳同位素地球化学：对石油成熟度、来源特征和充注方向的启示

摘要 塔里木盆地塔北隆起托弗台凸起近年来成为油气勘探的热点。使用气相色谱-质谱法和稳定碳同位素分析法分析了来自托弗台凸起 15 口井的 15 个奥陶系石油样品的生物标志物和碳同位素，以限制其沉积环境、热成熟度、烃源岩和可能的石油充注方向。样品的特点是萜类化合物丰富，C29 正甾烷和二苯并噻吩含量相对较高，Pr/Ph 和 C22/C21 三环萜烷的比例相对较低，C35/C34 高品烷的比例较高。结果表明，油的源岩沉积在还原性海相碳酸盐和泥灰岩环境中。寒武系和奥陶系烃源岩对原油贡献较大，中上奥陶统烃源岩贡献较大。饱和馏分中的正烷烃和丰富的 25-降霍烷表明该油是早期生物降解油和后期加入的晚期正常原油的混合物。来自甲基二金刚烷参数的数据表明原油处于高成熟阶段。石油充注示踪表明，优先运移方向主要为自南向北，与顺托果勒下隆起至塔北隆起以南沿神北一号断裂的石油运移有关。饱和馏分中的正烷烃和丰富的 25-降霍烷表明该油是早期生物降解油和后期加入的晚期正常原油的混合物。来自甲基二金刚烷参数的数据表明原油处于高成熟阶段。石油充注示踪表明，优先运移方向主要为自南向北，与顺托果勒下隆起至塔北隆起以南沿神北一号断裂的石油运移有关。饱和馏分中的正烷烃和丰富的 25-降霍烷表明该油是早期生物降解油和后期加入的晚期正常原油的混合物。来自甲基二金刚烷参数的数据表明原油处于高成熟阶段。石油充注示踪表明，优先运移方向主要为自南向北，与顺托果勒下隆起至塔北隆起以南沿神北一号断裂的石油运移有关。