【摘要】 目前,我国的氦气资源主要依赖进口,寻找大中型高含氦天然气田是改变这一现状最现实的途径。为此,对四川盆地威远地区高含氦天然气藏的成藏机理和氦气来源进行了分析,以探讨在该盆地前震旦系勘探高含氦天然气藏的可行性。首先根据盆地周缘12条野外露头剖面和4口钻穿震旦系单井的资料,系统分析了前震旦系的岩石学、沉积相、烃源岩等特征,认为前震旦系发育的沉积地层为南华系,东南缘露头剖面的地层序列为南沱组、大塘坡组、古城组和莲沱组,推测盆地内部可能发育相同的地层序列;南沱组、古城组和莲沱组主要为冰川沉积,为砂砾岩夹泥岩;而大塘坡组为间冰期沉积,发育一套砂泥岩地层,其下部泥页岩的有机质含量高,为较好烃源岩。进一步的研究表明:南沱组砂砾岩储层、大塘坡组烃源岩和地层中侵入的花岗岩"氦源岩"可形成较好的高含氦天然气藏成藏组合;前震旦系沉积岩的分布主要受早期裂谷控制,在裂谷内部充填厚层的沉积岩地层。结合地震资料预测了威远—资阳地区沉积岩和花岗岩的分布,结论认为在资阳地区对震旦系—前震旦系进行高含氦天然气藏的勘探是可行的。更多还原

【Abstract】 The consumption of helium in China highly depends on imports at present so it is the most practical way searching for medium-to-large high-helium natural gas fields.Based on the studies of the hydrocarbon accumulation mechanism and the helium origin of the Weiyuan high-helium natural gas reservoir,we discussed the feasibility of such exploration in the Presinian strata of the Sichuan Basin,where twelve outcrop sections around here and data of four wells in the Presinian strata were integrated to systematically analyze the petrological features,sedimentary facies and source rocks.It was believed that the sedimentary formation developed in the Presinian is the Nanhua system,and the stratigraphic sequence on outcrop section in the eastern margin,which may also occur within this basin,consists of the Nantuo,Datangpo,Gucheng and Liantuo groups.The Nantuo,Gucheng and Liantuo groups are mainly glacial deposits consisting of glutenites interbedded by mudstone;the Datangpo group is interglacial deposits consisting of sandstones and shales,the lower part of which is organic-rich shales with good source rock quality.Thus,the Nantuo coarse-grained clastic reservoirs,the Datangpo source rocks and the intruded granite "helium source rock" possibly formed good high-helium gas systems.The distribution of the Presinian sedimentary rocks was mainly controlled by the early rifting.Thick sedimentary rocks were deposited inside the rift.The prediction of sedimentary rocks and granite distributions in the Weiyuan and Ziyang areas by use of the seismic data revealed that it is feasible to explore high-helium gas reservoirs in the Ziyang area,Sichuan Basin.更多还原