塔里木盆地塔河油田石炭系、三叠系原油地球化学特征及成因研究

Geochemical Characteristics and Genesis of Crude Oils of Carboniferous and Triassic in Tahe Oil field of Tarim Basin

塔河油田是塔里木盆地迄今为止最大的海相碳酸盐岩油田,其成因备受关注。本文通过采样和气相色谱-质谱联用仪（GC-MS）分析,研究了塔河油田石炭系和三叠系原油地球化学特征及成因,研究结果表明：原油中Pr/Ph比值相对较低,Pr/nC17和Ph/nC18相关图反映其形成于还原环境;原油中含有相对丰富的伽马蜡烷和C30＋藿烷,说明原油形成于海相咸水环境;原油中含有丰富的三环萜、四环萜和较高的三环萜烷/藿烷,指示其母质来源为菌藻类;原油中重排甾烷/规则甾烷、Ts/（Ts＋Tm）和C29ββ/（ββ＋αα）参数值分别为0.24~0.40,0.28~0.50和0.56~0.63,均指示原油为成熟原油;25-降藿烷的检出说明原油受到一定的生物降解;油源对比研究表明塔河油田石炭系和三叠系原油主力烃源岩为中上奥陶统烃源岩。

Because Tahe oil field is the largest marine carbonate rock oil field of the Tarim Basin,its genesis is of great interest.By means of to the high-resolution GC-MS analysis of the oil samples from Carboniferous and Triassic Tahe oil field,this paper studies biomarkers and discuss their genesis.The Pr/Ph,Pr/nC 17 and Ph/nC 18 data indicated that oil formed from sapropel organic matters of reducing environment.Abundance of gammacerane C 30 ＋ hopane indicates that the oils formed from saltwater environment.The abundance of C 27 sterane,tricyclic terpane,tetracyclic terpane,and higher tricyclic terpane vs hopane parameters show that original source materials are homonemeaes.Rearranged sterane/sterane,Ts/（Ts＋Tm）,and C 29 ββ/（ββ＋αα） are 0.24~0.40,0.28~0.50 and 0.56~0.63,respectively.All of these show that the maturity of the oil is high.The occurrence of 25-norhopane indicates that the oil experienced some degree of biodegradation.Comparison of oil and source rock suggests that the oils of the main source rock came from the middle-upper Ordovician source rocks.