川东华蓥黄龙组沥青有机地球化学及油源对比

Organic Geochemical Characteristics and Oil Source Comparison of Bitumen from Huanglong Formation of Huaying in Eastern Sichuan Basin

华蓥溪口镇石炭系黄龙组白云岩孔洞中充填大量固体沥青,野外采集了沥青及不同烃源岩层系样品,进行了沥青有机地球化学特征研究及来源分析。结果表明,黄龙组沥青白云岩有机碳含量较高,R_o为1.45%~1.48%,碳同位素-28.90‰(PDB),饱和烃及芳烃含量较低,以非烃为主;正构烷烃主峰碳为C_(20),Pr/Ph为0.78~0.79,三环萜烷中C_(23)>C_(24)>C_(21),三环萜烷/五环萜烷为0.82~1.06,甾烷中C_(27)>C_(29)>C_(28),其中,C_(27)规则甾烷占优势,表明黄龙组沥青生烃母质以低等水生生物为主,为还原环境。萜烷参数及Ts/(Tm+Ts)均表明沥青成熟度较高。DBT/P为1.48~1.88,表明母岩可能为海相泥灰岩沉积。经生物标志物及沥青同位素综合对比,认为黄龙组固体沥青来自于龙马溪组页岩,氯仿沥青"A"抽提物具有混源特点,可能为龙马溪组页岩和栖霞组泥灰岩共同贡献的结果。

The void of the dolomite of Huanglong Formation in section of Xikou town of Huaying are filled with a large amount of bitumen,in the field,samples of asphalt and source rocks of different strata were collected in the study area and adj acent areas to explore the organic geochemical characteristics and sources of bitumen.The results show that the content of organic carbon in the bitumen-bearing dolomite of Huanglong Formation is high,the value of Ro is 1.45%to 1.48%,the value of carbon isotope is-28.90‰,the content of saturated hydrocarbon and aromatic hydrocarbon are low,mainly non-hydrocarbon;the main peak carbon of paraffins is C20,the value of Pr/Ph ratios from 0.78 to 0.79,the content of tricyclic terpanes C23>C24>C21,the ratio of tricyclic terpanes to pentacyclic terpanes are from 0.82 to 1.06,in Sterane,the content of C27>C29>C28,C27 gonane is dominant,these parameters indicate that the sedimentary environment is reductive.The value of terpane parameters and Ts/(Tm+Ts)all indicate high maturity of bitumen.The value of DBT/P is from 1.48 to 1.88,indicating that the parent rock may be Marine marl deposit.According to the comprehensive comparison of biomarkers and bituminous isotopes,it is considered that the solid bitumen of Huanglong Formation comes from the earlier mature shale of Longmaxi Formation,the extraction of chloroform bitumen"A"has the characteristics of mixed source,which may contribute to the shale of Longmaxi Formation.