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川西龙门山北段沥青脉与油苗广泛分布,尤其是下寒武统沥青脉,说明在龙门山褶皱带北段东缘具有寻找震旦系—寒武系油藏的良好前景。尽管有关该区下寒武统沥青脉的来源研究取得了一些进展,但具体来源于那套烃源岩还存在较大的分歧,同时对固体沥青脉的油气生成时间还缺乏系统研究。铼—锇(Re—Os)同位素测年法作为一种创新性的油气成藏定年方法,可对川西龙门山北段矿山梁下寒武统沥青矿的油气生成时间及其来源进行探索研究。通过系统的条件实验,建立了固体沥青、原油中沥青质提取、溶样、Re—Os纯化富集及分离等前处理技术及Re—Os同位素测年方法,主要步骤依次为样品制备、样品酸化学消解、Re和Os纯化富集与化学分离、Re和Os含量与同位素比值分析、Isoplot软件处理等。川西广元地区下寒武统沥青脉Re—Os同位素年代学及其油源分析研究表明,下寒武统固体沥青热成熟度低,油气生成时间早,约在572~559Ma之间,对应于新元古代晚震旦世,反映其来源于时代古老的烃源岩;从固体沥青Re—Os等时线年龄、初始187 Os/188 Os比值、碳同位素组成以及生物标志物等综合研究表明下寒武统沥青脉来源于震旦系陡山沱组优质烃源岩,该烃源岩于572~559Ma期间在低成熟阶段生成的稠油,进入灯影组地层中形成古稠油藏,后期由于构造抬升,震旦系灯影组古油藏破坏形成了现今的沥青脉。
Asphalt veins and oil saplings are widely distributed in the northern Longmenshan section of western Sichuan, especially the Lower Cambrian asphaltic veins, indicating that there is a good prospect of searching for Sinian-Cambrian reservoirs on the eastern margin of the northern segment of the Longmenshan fold belt. Although some progresses have been made in the source of the Lower Cambrian asphaltic veins in this area, there are still many differences between the source rocks and those of the source rocks. At the same time, there is a lack of systematic research on the hydrocarbon generation time of solid asphalt veins. Re-Os isotope dating method As an innovative method of hydrocarbon dating, it is possible to explore the hydrocarbon generation time and source of the Lower Cambrian asphaltic mines from the Beilian area in northern Longmenshan, western Sichuan. Through systematic experiments, the solid bitumen, asphaltene extraction, sample solution, purification and enrichment of Re-Os in crude oil, pre-treatment technology and Re-Os isotope dating method are established. The main steps are followed as sample preparation, sample acid Chemical digestion, purification of Re and Os enrichment and chemical separation, Re and Os content and isotope ratio analysis, Isoplot software processing. The Re-Os isotopic dating of the Lower Cambrian asphaltene vein and its oil source analysis in the Guangyuan area of western Sichuan shows that the Lower Cambrian solid bitumen has low thermal maturity and early hydrocarbon generation, which is between 572 and 559Ma, corresponding to the new In the late Paleozoic Sinian, it was derived from the ancient source rocks of the age. From the comprehensive study of Re-Os isochron age, initial 187 Os / 188 Os ratio, carbon isotope composition and biomarkers of solid bitumen, The archeological asphalt veins originated from the high-quality source rock of the Sinian Doushantuo Formation. The heavy oil formed during the low-mature stage of 572-595 Ma during the formation of the paleosol reservoir into the Dengying Formation, Uplift, the Sinian Dengying group of ancient reservoirs destroyed the formation of today’s asphalt veins.