辽西金羊盆地北票组油砂饱和烃地球化学特征--以SZK02井为例

Saturated hydrocarbon geochemical characteristics of the oil sand from Beipiao Formation in Jinyang Basin,western Liaoning Province:A case study of SZK02 Well

在金羊盆地SZK02钻孔中,相继发现4件岩心样品有油气显示,对该井已发现的油砂采用气相色谱、气相色谱-质谱技术进行了分析测试。荧光薄片鉴定显示,岩石粒间普遍被油质沥青浸染,油砂生物标志化合物特征总体表现为正构烷烃丰富、姥植比高、重排藿烷和重排甾烷含量高,指示为偏氧化性的湖沼相沉积环境,有机质演化处于成熟-高成熟阶段。依据生物标志物特征,油砂可分为2种类型:Ⅰ类油砂位于SZK02井较浅部,以高重排补身烷、Ts、C30重排藿烷及未知结构的C30-早洗脱重排藿烷的组合为特征;Ⅱ类油砂位于SZK02井较深部,以较高含量的8β-升补身烷、相对低的Ts/Tm值,五环三萜烷中C30藿烷为主峰的组合为特征。初步的油源对比结果认为,其来源于2种不同类型的烃源岩贡献。

There have been found four oil and gas shows from SZK02 well in Jinyang Basin. Using gas chromatography and gas chromatography mass spectrometry techniques, the authors studied the characteristics of biomarker compounds of Beipiao Formation oil sand. Thin fluorescent display identification shows that disseminated oily bitumen widely exists between rock grains; the characteristics of biomarker compounds of oil sand reveal abundant n-alkanes and high level of Pr/Ph ratio and show dominant distribution of re（H）-hopanes and rearranged sterane, which suggests that the oil sand was formed in an oxidized lacusrtine facies environment. The organic matter evolution is at a mature to highly mature stage. According to the distribution and geochemical compositions of biomarkers, the oil sand could be divided into two types. Type one is found to be located at the shallow depth of the SZK02 well, which reflects abundant re-drimane, Ts, C30-re（H）-hopanes and structurally-unknown C30-re（H）-hopanes. Type two is found to be located at the deep depth of the SZK02 well, which generally has abundant 8 β-homodrimane, relatively low Ts/Tm ratios and domi-nant C30-hopanes in the pentacyclic triterpenoid. The results of oil and source correlation show that oil sand is mainly derived from two different source rocks.