塔里木盆地顺北油气田1号和5号断裂带奥陶系油气藏特征

综合运用油气地球化学分析技术对顺北油气田1号和5号主干断裂带奥陶系油气藏进行研究,并结合油气物理性质和烃类相态特征等数据资料来开展不同断裂带上油气藏特征精细对比,从而探讨不同断裂带油气藏特征差异成因。结果表明,两条不同断裂带油气藏的油气源特征相似,均来自于还原性较强的腐泥型生烃母质,且均处于高成熟演化阶段,但顺北1号断裂带为未饱和挥发油藏,顺北5号断裂带为未饱和轻质油藏,1号断裂带油气成熟度明显高于5号断裂带。两条断裂带油气藏特征出现差异主要与顺北地区不同的油气充注过程和后期改造作用有关:顺北地区可能存在3期油气充注,5号断裂带油气藏为前两期油气的混合充注,最早一期油气遭到破坏,以第二期油气充注为主,而1号断裂带油气藏以最晚的第三期油气充注为主;两条断裂带油气藏均未经历明显的热裂解作用,但是1号断裂带原油经历轻微的硫酸盐热化学还原改造作用(TSR),而5号断裂带早期充注原油经历过生物降解作用(BSR)。不同的油气充注过程是导致顺北地区不同断裂带油气藏特征差异的主要因素。

Characteristics of Ordovician reservoirs in Shunbei 1 and 5 fault zones,Tarim Basin

The Ordovician reservoir characteristics in two major fault zones (Shunbei 1 and 5) in the Shunbei area of the Tarim Basin were studied by integrated petroleum geochemical analysis techniques.The reservoir characteristics in the two fault zones are finely described and compared based on petroleum physical properties and hydrocarbon facies attributes, with a view to obtaining the origin of differential characteristics for reservoirs in different fault zones.The results show that the two fault zones share similar oil-gas sources of sapropelic hydrocarbon-generating parent materials with strong reducibility and of high thermal maturity.However, the Shunbei 1 fault zone has unsaturated volatile oil reservoirs, whereas the Shunbei 5 fault zone has unsaturated light oil reservoirs; and the maturity of oil and gas from the Shunbei 1 fault zone is significantly higher than that from the Shunbei 5 fault zone.These differences could be attributed to the multi-stage oil and gas charge and later reformation in the Shunbei area, which may have undergone three stages of hydrocarbon charge.The reservoirs in the Shunbei 5 fault zone were formed by both the first and second stages of hydrocarbon charge (mainly by the second stage as the hydrocarbon from the first stage of charge was mostly dissipated due to some damage) and those in the Shunbei 1 fault zone were largely the result of the third stage of hydrocarbon charge.Neither fault zones have undergone obvious thermal cracking, except for a slight thermochemical sulfate reduction (TSR) to the crude in the Shungbei 1 fault zone, and BSR to the early charged crude in the Shunbei 5 fault zone.Different charging processes are the main factors leading to different reservoir characteristics of different fault zones in the Shunbei area.