荧光光谱技术在页岩油地质评价中的应用

Application of fluorescence spectroscopy in geological evaluation of shale oil

页岩的纹层状构造特征导致其具有强非均质性,研究页岩的含油性需要高精度、高分辨率的技术手段。同步荧光光谱(SFS)法和全息扫描荧光光谱(TSF)法在页岩非均质性研究中有较好的应用前景,可聚焦到纹层尺度进行微区分析。对渤海湾盆地和四川盆地不同成熟度页岩样品开展的荧光光谱分析表明,随着有机质热演化程度加深,页岩中可溶有机质的荧光峰具有先红移后蓝移、荧光强度逐渐降低的变化特征。荧光参数R代表了三环芳烃与四环芳烃的总荧光强度与二环芳烃荧光强度的比值,可作为一种成熟度指标。当页岩进入生油窗后,其R>1.5,并随着成熟度增大,R逐渐减小;对于进入高成熟的热演化生气阶段的页岩,当其R表现出无明显变化规律时,荧光强度越小,演化程度越高。结合主成分分析和回归分析,建立了基于荧光参数表征页岩含油量的定量计算模型,达到在纹层、岩心尺度上评价不同岩相不同纹层中页岩油赋存情况的目的。

Shale possesses strong heterogeneity because of its lamellar structure. High-precision and high-resolution technical means are required for studying shale oiliness. Synchronous fluorescence spectroscopy(SFS)and total scanning fluorescence(TSF)have good application prospects in research of shale heterogeneity, and they can focus on the layer size for micro-zone analysis. The fluorescence spectrum analysis of shale samples with different maturities from Bohai Bay Basin and Sichuan Basin shows that the fluorescence peak of soluble organic matters in shale shows a red shift first and blue shift later, as well as gradual decrease of fluorescence intensity with the thermal evolution of organic matters. The fluorescence parameter Rrepresents the ratio of the total fluorescence intensity of tricyclic and tetracyclic aromatic hydrocarbons to the intensity of bicyclic aromatic hydrocarbon and can be used as a maturity index. When shale has entered into the oil generation window, Ris greater than 1.5. With the increasing of the maturity, Rdecreases gradually. For the shale entering the stage of highly mature thermal evolution and gas generation, when Rshows no obvious change law, the lower the fluorescence intensity, the higher the evolution degree. Further, according to the principal component analysis and regression analysis, a quantitative calculation model of shale oil content based on fluorescence parameters is established to carry out the evaluation of shale oil occurrence in different lithofacies and laminated reservoirs on the scale of laminae and cores.