川东北飞仙关组储层固体沥青地球化学特征及其气源指示意义

Geochemical Characteristics of Solid Bitumen in Reservoir and Their Implication for the Origin of Natural Gas of Feixianguan Formation in Northeastern Sichuan Basin

运用有机岩石学、有机地球化学、催化加氢热解、GC—IRMS等方法和技术,深入研究了川东北飞仙关组储层固体沥青及可能烃源岩的地球化学特征。研究认为,飞仙关组储层固体沥青反射率高,双反射明显,为非均质结构储层焦沥青;在碳酸盐岩储层的各种孔隙中,呈脉状、球粒状、角片状或块状等他形充填,具有中间相结构和镶嵌状结构特征,反映其高温热变质成因;元素组成有S/C高、H/C低的特点,其固体碳同位素组成与长兴组烃源岩干酪根相似。储层固体沥青的可能烃源岩发育于还原—弱氧化咸水沉积环境,有机质来源于水生藻类;氯仿沥青"A"饱和烃甾萜类生物标志物对比表明,上二叠长兴组烃源岩是主要来源,飞仙关组、下志留统烃源岩亦有贡献;催化加氢产物饱和烃及其正构烷烃单体碳同位素组成显示,坡2井飞仙关组储层固体沥青与罐5井飞仙关组烃源岩具有明显的亲缘关系,这也可作为飞仙关组海槽相烃源岩对飞仙关组气藏有贡献的佐证。

Systemic geochemical analyses such as organic petrology, geochemistry, catalytic hydropyrolysis and GC-IRMS show that, the solid bitumen in reservoir of Feixianguan Formation in northeastern Sichuan basin are residuals （pyrobitumen） generated from oil cracking, they have double reflection, high reflection ratio, high S/C and low H/ C. Changxing Formation is the primary hydrocarbon source reck for the solid bitumen, while Feixianguan and lower Silurian are the subordination, according to the carbon isotopic compositions of the insoluble constituent and the biomarkers such as sterane and terpane in saturated hydrocarbons of the solvent extracts. There is an obviously genetic relationship between the solid bitumen in Well Po2 of Feixianguan Formation and the keregen （derived from the hydrocarbon source rock） in Well Guan5 of Feixianguan Formation according to distribution and molecular carbon isotopic compositions of the saturated hydrocarbon Feixianguan Formation has contributions to the of catalytic hydropyrelysis products. gas pools of Feixianguan Formation Conclusion that the source rock in can be acquired.