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陆南地区侏罗系和白垩系油气勘探获得重大突破,但其油气成因及来源存在争议。采用全烃地球化学方法,对天然气、原油轻烃和生物标志物特征进行分析,并与周缘构造油气特征进行对比,明确了陆南地区油气成因及来源。该区原油碳同位素较轻,轻烃庚烷值和异庚烷值较小,甲基环己烷含量较高,C_(28)甾烷丰度较低,与莫北凸起原油明显不同,与滴南凸起南分支原油和东道3井白垩系储层抽提物特征基本一致;天然气组分和甲、乙烷碳同位素特征与莫北凸起天然气以及典型的石炭系来源天然气均不同。结合区域构造和烃源岩分布特征,指出陆南地区浅层原油和天然气源区均为东道海子凹陷,原油主要为二叠系平地泉组成熟阶段产物,并存在侏罗系源岩成熟阶段产物的混合;天然气主要为石炭系高—过成熟阶段产物,存在二叠系来源的成熟阶段产物的混合。该区下步勘探应往东道海子凹陷延伸,凹陷北斜坡迎烃面大量发育的岩性圈闭和构造-岩性圈闭具有巨大勘探潜力。
The Jurassic and Cretaceous hydrocarbon exploration in Luonan area has made a significant breakthrough, but the origin and origin of oil and gas are controversial. All hydrocarbon geochemical methods were used to analyze the characteristics of natural gas, light hydrocarbon and biomarkers of crude oil, and compared with the features of petroleum in the peripheral structure. The causes and sources of hydrocarbon in Luonan area were clarified. In this area, the carbon isotopes of crude oil are lighter, the values of light heptane and isoheptane are smaller, the content of methylcyclohexane is higher, the abundance of C 28 sterane is lower, which is obviously different from the crude oil of North MoBu protuberance, Which is basically the same as that of the south branch crude oil from the southern drop and the Cretaceous reservoir extract from the Dongdao-3 well. The carbon isotope characteristics of natural gas components and methane and ethane are different from the natural gas from the Mobei convex and the typical Carboniferous source gas. Based on the regional tectonics and the distribution of source rock, it is pointed out that the shallow oil and natural gas source areas in Lunan area are both Dongdao Haizi sag, and the crude oil is mainly the mature stage product of Permian Pingdiquan Formation, and the mature stage product of Jurassic source rocks . The natural gas is mainly the high-percolation stage of Carboniferous, and there is a mixture of mature stages of Permian source. The further exploration in the area should extend to the east Hagi depression. The lithologic traps and tectonic-lithologic traps with large development of hydrocarbon-bearing faces on the northern slope of the depression show great exploration potential.