塔里木盆地志留系沥青砂油源及充注期次分析——来自生物标志化合物的证据

Source Recognition and Charging Analysis of Oil in the Silurian Bituminous Sandstone in the Tarim Basin:Evidences from Biomarker Compounds

通过对塔里木盆地志留系沥青砂岩抽提物的地球化学分析发现,沥青砂岩氯仿沥青＂A＂含量高（0.477 1%～1.410 3%）,抽提物饱和烃以及芳香烃＂三芴＂组成与塔河油田主体区原油具有一致的特征,与中—上奥陶统烃源岩具有可对比性;仅塔北地区TP7井氯仿沥青＂A＂含量较低,与氯仿沥青含量较高的沥青砂岩具有明显不同的三芳甾烷和甲基三芳甾烷分布,与典型的寒武系烃源岩特征一致。有机岩石学资料和显微镜观察均显示志留系沥青砂岩有机成熟度并不高,与生物标志化合物指示的成熟阶段相一致,指示其未经历较强的热演化历史。结合生物标志化合物证据和埋藏史分析认为,塔里木盆地志留系经历了来自寒武系和奥陶系烃源层的2期油气充注过程,塔北、塔中志留系沥青砂岩中丰富的油气显示和可动油流指示油气勘探前景广阔。

Elaborate and refined geochemical research work has been conducted on the Silurian bitumen sandstone extracts from the Tazhong Uplift and Tabei Uplift.Several explicit conclusions are summarized.Chloroform bitumen（＂A＂）ranges from 0.477 1%to 1.410 3%,implying the bitumen sandstone is petroliferous enough for crude oil production.The extract of bitumen sandstone shows much more similarity in the triaromatic dinoflagellates sterane distribution than that in most oils from the Tahe Oilfield and the potential source rocks have been regarded as the Middle-Upper Ordovician marls.Whereas chloroform bitumen（＂A＂）in well TP7 has much lower and different triaromatic steroids and triaromatic dinoflagellates sterane patterns which gives evidence of Cambrian source.Organic petrology data show bitumen in the sandstone is right in＂oil window＂,which is consistent with the mature information provided by the biomarker fingerprints Ts/（Ts＋Tm）vs 4-/1-MDBT.Two accumulation periods are recognized with the reconstruction of burial history of Well Ha9.It is proposed that the abundant oil show and movable oil flow enlighten great potential for the exploration in the Silurian bitumen sandstone.