原油中生物标志物的组成是成藏史的反映

COMPOSITION OF THE BIOMARKERS IN CRUDE OIL IS THE REFLECTION OF POOL-FORMING HISTORY

油藏中原油的生物标志化合物不仅可以指示生油岩的类型、成熟度，而且可以反映油藏的充注方向及成藏史．以济阳坳陷中的孤南洼陷和利津洼陷为例，利用生物标志化合物进行油源对比，区分出不同成因的原油，并确定了不同的成藏阶段．孤南洼陷的油田中有分别生成于沙一段和沙三段的原油；利津洼陷的油田中则是来自于沙三段和沙四段的原油．它们各自的成熟度指示成藏的期次和时间．沙一段和沙四段生油岩形成于咸水环境，开始生烃早，对应于Ｒｏ＝０．３５％～０．４０％，Ｃ２９甾烷ｗ（Ｓ）／ｗ（Ｒ＋Ｓ）＝０．１２～０．１５；沙三段生油岩为淡水湖相沉积，开始生烃较晚，对应于Ｒｏ＝０．４５％～０．５０％，Ｃ２９甾烷ｗ（Ｓ）／ｗ（Ｒ＋Ｓ）＝０．３０～０．３５．孤南凹陷两个成藏阶段，分别是渐新世末期及中新世；利津凹陷两个成藏阶段，分别为渐新世早期及末期．在断块盆地中，盆地中心部位的油藏以侧向充注为主，形成单源油藏；在断裂带，特别是边缘断裂带以垂向充注为主，常形成混源油藏．

The biomarkers in the pool oil can not only indicate the type and maturity of source rocks but also reflect reservoir filling direction and pool-forming history. In the case study of the Gunan and the Lijing depressions in the Jiyang Basin, the oils of different origins and pool-forming stages were identified as a result of the oil-source correlation by the biomarker. The crude oils from the oil fields in the Gunan depression originated from the first (Es1) and third (Es3) members of the Shahejie Formation, respectively. While the oils from the Lijing depression came respectively from the third and fourth (Es4) members. Their maturities indicate the pool-forming times and geological time. The source rocks of Es1 and Es4 were deposited in the saline environment and generated oil earlier, corresponding to Ro=0.35%～0.40% and C29 steranes w(S)/w(S+R)=0.10～0.15; The source rocks of Es3 were formed in the fresh lake and begun oil generation later, corresponding to Ro=0.45%～0.50% and w(S)/w(S+R)=0.30～0.35. Two pool forming stages in the Gunan depression mark the the end of the Oligocene and Miocene, those in the Lijing depression stand for the middle and the end of the Oligocene. In the faulted basin, the pools located inside the basin were mainly charging laterally, thus forming the pool with a single source. The pool-filling in the fault zone, particularly in the marginal faulted zone is mostly vertical, thus forming the pool with different sources.