喀什凹陷原油与油砂地球化学研究与油源分析

喀什凹陷是塔西南坳陷油气显示丰富的地区之一,也是塔里木盆地连接中亚油气勘探的前沿阵地,确定油气显示的油源特征对油气勘探具有重要的意义。研究了克拉托背斜北翼大量存在的原油和油砂抽提物的地球化学特征,评价了凹陷北缘库孜贡苏剖面侏罗系烃源岩和南缘炮江沟剖面石炭系烃源岩,得出了两套烃源岩的分子地球化学特征,确定了原油和油砂抽提物的油源。结果显示,中、下侏罗统粉砂质泥岩和下石炭统黑色碳质泥岩是该区较好的两套烃源岩,两者存在明显的分子地球化学特征差异;通过对饱和烃馏分中甾、萜烷和芳烃馏分中三芴化合物、三芳甾烷等生物标志物特征的刻画,发现喀什凹陷原油与中、下侏罗统烃源岩具对比性,克拉托背斜油砂抽提物的分子地球化学特征明显不同于中、下侏罗统烃源岩,而与下石炭统黑色碳质泥岩具有较好的对比,三芳甾烷证据认为早期石炭系烃源贡献可能对原油和油砂都有影响。油源的新认识对喀什凹陷下一步油气勘探具有一定决策参考。

Geochemical analysis of crude oils and oil sand in the Kashi Sag, Tarim Basin.

Proven as one of the most abundant oil and gas shows regions in Southwest Tarim Basin, the oil and gas discovery in Kashi Sag has been got much attention, but more and broad oil and gas breakthroughs are expected. Being a tunnel to link the oil and gas discovery between Tarim Basin and Middle Asia, this area has been a spotlight for further attention in geological study. And the first step to define the oil-source relationship is critical for next exploration work. This paper presents the geochemical fingerprints of crude oils and extract of oilsand in Kelatuo anticline, assesses the source rock we are collecting in the outcrop sections (Kuzigongsu Section and Paojiang Gou Section ) and defines the oil-source relationship in the Kashi Sag. Silty mudstone in Middle- Lower Jurassic and carbonaceous mudstone in Lower Carboniferous have been proven good source rock and we are giving significant differences between the source rocks. The geochemical fingerprints including terpanes, steranes in saturated components and fluorine- dibenzofuran- dibenzothiophene, triaromatic steroids in aromatics components indicate that the oils of Kashi Sag have been proven to be sourced from Kangsu and Yangye Formation in Middle- Lower Jurassic while the Kelatuo oil sand sources from the carbonaceous mudstone in Lower Carboniferous. For the tiny amounts of triaromatic steroids in Middle- Lower Jurassic silty shale, the detection of triaromatic steroids in both oils and oil sand possibly proves the Lower Carboniferous source contribution in the geological evlution.