塔北哈6井油砂及沥青砂岩抽提物的地球化学特征及对比

采集塔里木盆地哈拉哈塘凹陷哈6井石炭系油砂及志留系沥青砂岩样品共5件,对其抽提并进行稳定碳同位素、饱和烃气相色谱及色谱/质谱等分析。石炭系油砂与志留系沥青砂岩抽提物的稳定碳同位素组成十分相似;CPI值为0.95~1.06,OEP值为0.94~1.00,姥鲛烷/植烷值为0.34~0.76;C21/C23三环萜烷为0.37~0.47,C29/C30藿烷为0.91~0.97,C35S/C34S藿烷为0.91~1.00,伽马蜡烷/C30藿烷为0.69~0.79,Ts/(Ts+Tm)为0.39~0.43,C27、C28、C29规则甾烷及芴、硫芴、氧芴的相对组成均非常接近。样品抽提物中正烷烃和类异戊二烯烃与25-降藿烷系列化合物和UCM鼓包共存。分析认为石炭系与志留系原油源自相同的烃源岩,两者均存在多期充注且遭受了不同程度的生物降解作用。

Geochemical characteristics and correlation of extracts from Silurian bituminous sandstones and Carboniferous oil sands in well Ha6, northern Tarim Basin

Five Silurian bituminous sandstone and Carboniferous oil sand samples were collected from well Ha6 in the Halahatang Sag of the Tarim Basin, and geochemical analyses including extraction, stable carbon isotope composition, saturate fraction gas chromatography and biomarkers were performed. The δ13C (‰) values for extracts from the Silurian bituminous sandstone and the Carboniferous oil sand samples are very close. The CPI values range from 0.95 to 1.06, the OEP values from 0.94 to 1.00, the Pr/Ph values from 0.34 to 0.76, the C₂₁/C₂₃ tricyclic terpane values from 0.37 to 0.47, the C₂₉/C₃₀ hopane values from 0.91 to 0.97, the C₃₅S/C₃₄S hopane values from 0.91 to 1.00, the gammacerane/C₃₀ hopane values from 0.69 to 0.79, the Ts/(Ts+Tm) values from 0.39 to 0.43. Besides, the relative concentration of C₂₇, C₂₈ and C₂₉ regular steranes for extracts from all samples is significantly similar and so does the relative concentration of fluorene, dibenzofurans and dibenzothiophene. Extracts from five samples all contain 25-norhopanes and n-alkanes and acyclic isoprenoids with different abundance and the saturated fraction gas chromatograms show baseline humps called UCM, i.e., n-alkanes and acyclic isoprenoids co-exist with UCM and 25-norhopanes. Based on the above analyses, it was concluded that Silurian and Carboniferous oils were derived from same source rocks and had undergone multiple charges and different degrees of biodegradation.