Medium-light oils were tested in well YQX1 in the Ordovician super heavy oil area in the northwest of Tahe Oil Field. We studied their geochemical characteristics including physical character, group composition, GC-MS of saturated and aromatic hydrocarbons, and made a comparison with the Ordovician super heavy oils in the Yuqi area and the condensate oils in the Yakela area, in order to confirm their genetic types. The medium-light oils from well YQX1 have a high saturate hydrocarbon content, medium aromatic hydrocarbon content, and low non⁃hydrocarbon and asphaltene contents. The n⁃alkane series is complete with a single mode. An obvious“UCM” hump appears in chromatogram. The distributions of steranes and terpanes has a good correlation with the super heavy oils of Yuqi area and the condensate oils of Yakela area, which indicates that they have the same source. Maturity parameters such as Ts/( Ts+Tm) and 4-/1-MDBT show that oils from well YQX1 have a high maturity, which is similar to the condensate oils in Yakela and higher than the super heavy oils of the Yuqi area. Combined with terminal accumulation background and tectonic evolution in the northwest of Tahe Oil Field, it is inferred that the oils from well YQX1 mainly came from the north. The high⁃maturity light oil and gas migrated along the Luntai fault during the Himalayan period, transformed the early heavy oil reservoirs along unconformity from north to south, and finally formed the medium-light oil currently present in the reservoir.%于奇西1（ YQX1）井在塔河油田西北部奥陶系超重质油区获稳产中—轻质油流，为了确定其原油成因，作者通过与邻区奥陶系超重质油、雅克拉凝析油的物性、族组成、饱和烃、芳烃色谱—质谱等地球化学特征对比，发现YQX1井原油具有高饱和烃、中等芳烃、低非烃和沥青质的特征，正构烷烃系列分布完整，呈单峰前峰型分布，色谱图上出现较强的“UCM”鼓包。甾萜烷分布与于奇西超重质油以及雅克拉凝析油具有相似性，确定其同源；而Ts／（ Ts＋Tm）、4－／1－MDBT等成熟度参数对比显示，YQX1井原油成熟度较邻区超重质油藏高，而和雅克拉凝析油相近，属高成熟原油。结合塔河西北部晚期的油气成藏背景和构造演化特征，尤其是轮台断裂在喜马拉雅期的控油作用，推断YQX1井中—轻质油主要来自北部。喜马拉雅晚期的高成熟轻质油气沿轮台断裂运移，至奥陶系顶部不整合面由北向南对前期的超重质油藏进行混合改造，形成了一定范围的中—轻质油藏。
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