激光拉曼光谱在有机包裹体研究中的应用r——以苏里格气田西部盒8段油气包裹体为例

摘要

Based on the application of laser raman microprobe analysis in situ technique, the nature of oil and gas inclusions in the 8th member of the Shihezi formation in western Sulige gas field was identified. The composition and relative molar fraction of phaseⅡhydrocarbon-bearing organic inclusions in the healing fracture of the quartz grain surface and in the secondary enlargement margin were determined. The results show that the early-stage inclusions mainly are gas-liquid two-phase organic inclusions containing gaseous hydrocarbon and brine gaseous hydrocarbon, and the late-stage inclusions are gas-liquid two-phase organic inclusions containing gaseous hydrocarbon; The gas phase is dominated by gases such as CO2 , CH4 and N2 , and the CO, H2 S, H2 , C2 H2 , C2 H4 , C2 H6 , C4 H6 , H2 O and CO2 are dissolved in it; the liquid phase mainly is consist of H2 O and CO2 , and also contains a very small amount of anion SO2-4 and CO2-3 ( less than 0. 03 mol/L) . The research makes clear that the early-stage organic inclusions contain large amounts of CO2 , H2 O and a small amount of inorganic gas of low carbon alkane. It indicates that the early maturity of organic matter was in immature-low mature stage. Although natural gas is generated, the migration is limited in scale. The organic inclusions are few and far between. It reflects the replacement of formation water by natural gas entering reservoir. The late-stage organic inclusions are the opposite. The content of hydrocarbons and N2 are higher, but the content of CO2 , inorganic gas and H2 O are lower. It represents the characteristics of the peak of oil and gas formation and large-scale oil and gas accumulation. It provides a scientific basis for the thermal evolution of organic matter, the generation and migration of oil and gas, and the division of oil and gas accumulation stages.%以苏里格气田西部盒8段储层砂岩油气包裹体为例,应用激光拉曼探针微区原位分析技术,对其赋存于石英颗粒表面愈合裂隙、 次生加大边的2期含烃有机包裹体的成分及其相对摩尔百分含量进行测定:早期包裹体主要为含气态烃和含盐水气态烃的气液两相有机包裹体,晚期包裹体为含气态烃气液两相有机包裹体;其气相成分以CO2、CH4和N2等气体为主,溶解有CO、H2 S、H2、C2 H2、C2 H4、C2 H6、C4 H6等气体;液相成分以H2 O和CO2为主,此外还含有极少量的阴离子SO2-4和CO2-3离子(小于0.03 mol/L).研究表明:早期有机包裹体含有大量CO2无机气体、H2 O和少量低碳烷烃,说明早期有机质成熟度处于未成熟—低成熟阶段,虽有天然气生成,但运移规模有限,形成的有机包裹体极少,反映了天然气进入储层后置换地层水的过程;晚期有机包裹体与之相反,烃类和N2含量均较高,而CO2无机气体和H2 O含量均较低,可见晚期有机包裹体代表了油气形成高峰和大规模进入储层成藏期间的流体特征,为有机质的热演化程度,油气生成、 运移,划分油气成藏期次提供了科学依据.