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浅层天然气是当前国内外天然气勘探和基础研究的一个热点,在准噶尔盆地是油气勘探的一个重要新领域,但研究程度较低。为给区域勘探和成藏研究提供信息,并为国内外同类研究对比参考,主要以盆地腹部地区为例,着重从地球化学角度,包括系统的天然气组分、烷烃系列碳同位素组成、轻烃等,结合与天然气共生凝析油和储层沥青的研究,揭示了浅层天然气具有多种成因。研究区浅层天然气主要分布在陆梁、滴西、滴北和白家海4个地区。其中,陆梁地区浅层天然气成因为原油次生生物降解气,典型地球化学特征是气组分很干,几乎全为甲烷组成,甲烷碳同位素特别轻(–55‰~–45‰)。滴西地区浅层天然气以石炭系来源煤型气为主,兼有二叠系来源煤型气和油型气,典型特征是乙烷碳同位素值变化大(–30.67‰~–22.20‰)。滴北地区浅层天然气为石炭系来源煤型气,典型特征是乙烷碳同位素重(–24.54‰~–23.72‰)。白家海地区浅层天然气为二叠系来源高成熟煤型气,典型特征是干燥系数大(0.97),甲烷碳同位素重(–30.15‰~–29.45‰),乙烷碳同位素较重(–25.83‰~–25.81‰)。因此,研究区浅层天然气具有多种成因,主要包括来自不同烃源的原油次生生物降解气、油型气和煤型气,这预示着成藏的复杂性,需在下一步的勘探中给予充分重视。
Shallow gas is a hot spot of natural gas exploration and basic research both at home and abroad. It is an important new field of oil and gas exploration in the Junggar Basin, but the degree of research is relatively low. In order to provide information for regional exploration and reservoir formation research and reference for similar studies both at home and abroad, this paper mainly focuses on the geochemical aspects of the belly of the basin, including the natural gas components of the system, the carbon isotope composition of alkanes, light hydrocarbons , Combined with the study of natural gas condensate and reservoir asphalt, reveals that shallow gas has many causes. The shallow natural gas in the study area is mainly distributed in Luliang, Dixi, Xibei and Baijiahai areas. Among them, the shallow natural gas in Luliang area is caused by the secondary biodegradable gas of crude oil. The typical geochemical characteristics are that the gas components are very dry, almost all are methane, and the methane carbon isotopes are particularly light (-55 ‰ ~ -45 ‰). The shallow natural gas in the area of Xixi mainly consists of Carboniferous source coal gas, which is also of Permian source coal gas and oil gas. The typical feature is that the carbon isotope value of ethane varies greatly from -30.67 ‰ to -22.20 ‰. Shallow gas in the northeastern region is a Carboniferous source coal gas, typical of which is carbon isotope weight (-24.54 ‰ -23.72 ‰). The shallow natural gas in the Baijiahai area is a high-mature coal gas of Permian origin. The typical characteristics are high dry coefficient (0.97), heavy carbon isotope (-30.15 ‰ ~ -29.45 ‰) and heavy carbon isotope (-25.83 ‰ ~ -25.81 ‰). Therefore, the shallow natural gas in the study area has a variety of causes, including mainly crude oil secondary biodegraded gas, oil gas and coal gas from different hydrocarbon sources, which indicates the complexity of hydrocarbon accumulation and needs to be given in the next exploration Pay full attention.