渤深6潜山天然气成因及成藏条件

Origin of natural gas and formation conditions of gas reservoir in Boshen 6 buried-hill

孤西断裂带深层天然气来源多,成因复杂,混源现象普遍.针对这一问题,运用天然气组分、稳定碳同位素、轻烃组成、稀有气体同位素和伴生原油生物标志物等多种指标,与邻区天然气进行对比,认为该区带中渤深6潜山下古生界天然气主要为高成熟油型气,混有部分伴生气;天然气与原油同源,主要源自渤南洼陷Es4上烃源岩,也存在Es3下烃源岩的贡献.成藏条件分析表明:气源条件充足,储盖组合良好,沟通油气源的断层和不整合面发育,生烃期晚,天然气保存有利,是该区油气富集的关键.

The deep natural gas in Guxi fault zone is characterized as multi-source and complex genesis,and mixing-source gas reservoirs are generally formed.In view of this problem,the geochemical characteristics and genesis of Lower Paleozoic natural gas of Boshen 6 buried-hill in Guxi fault zone is clarified based on the chemical component,carbon isotope,light hydrocarbon composition,rare gas isotope of the natural gas,the biomarkers of associated crude oil,and the comparison of the indexes of the natural gas with those of the natural gas nearby.It is held that the natural gas is mainly composed of high-mature oil-type gas and it contains a part of oil-associated gas.The natural gas and the associated oil are mainly from the upper Es4 source rocks in Bonan Sag,and there is a little contribution of lower Es3 source rocks.The research of reservoir formation conditions shows that the key factors to hydrocarbon enrichment in Boshen 6 buried-hill include sufficient gas source,favorable reservoir-seal assemblage,faults and unconformities linking up source and reservoir,late stage of hydrocarbon generation and beneficial gas preservation conditions.