油气组分及同位素组成特征在莺琼盆地油气二次运移研究中的应用

APPLICATION OF CONTENTS OF CHEMICAL COMPONENTS AND ISOTOPIC COMPOSITION OF OIL-GAS TO RESEARCH ON THE SECONDARY MIGRATION OF YING-QIONG BASIN IN CHINA

油气不同组分的物理化学特性差异及地层中岩石、矿物选择性吸附造成的色层效应使油气在运移过程中其组分和同位素组成发生一定的变化 ,这为利用油气地化特征探讨油气运移提供了理论基础。利用该原理对莺琼盆地崖 13 1气藏天然气甲烷δ13C1值及凝析油族组分 (烷烃、芳烃、胶质 )、C6化合物 (正构烷烃、异构烷烃、环烷烃、芳烃 )等的相对含量和碳同位素组成进行了研究。结果表明 ,该气藏中天然气甲烷及凝析油族组分的δ13C1值由西到东呈现逐渐变轻的趋势 ;凝析油中极性相对弱的组分含量逐渐增加 ,极性相对强的组分含量逐渐降低。这表明崖13 1气藏中的油气应主要来自一号断层西侧的莺歌海盆地 ,其运移方向是由西以东。对莺琼盆地东方 1 1气藏天然气甲烷δ13C1值的研究表明 ,该气藏主要是由下覆烃源岩生成的天然气向上运移到浅层形成的 ,气藏中大部分天然气的垂向运移距离在

Because of the difference of physical\|chemical property among the components of oil\|gas and the chromatographic effect resulted from selective absorption of rock and ore in stratum, the chemical components and isotopic content of oil and gas will change during migration. It could be the theoretical basis for employing geochemical properties of oil and gas in research on migration of oil and gas. The carbon isotopic content of methane, the relative content and the carbon isotopic composition of condensate's components (saturated\|hydrocarbon, aromatic\|hydrocarbon, and colloid) and those of C\-6\|components (normal\|alkane, isomertic\|alkane, cyclic\|hydrocarbon, and aromatic\|hydrocarbon) of natural gas from Ying\|Qiong basin are studied. The results show that the carbon isotopic content is reduced gradually from the west to the east of the basin. The contents of components with relatively weaker polarity increase gradually and that of components with relatively stronger polarity change decreasingly, which shows that the oil and gas in Ya 13\|1 gas reservoir in Ying\|qiong basin are mainly from Yinggehai basin beside the west side of No.1 Faultage, and the migration direction is from the west to the east. The carbon isotopic contents of methane of natural gas from Dongfang 1\|1 gas reservoir in Ying\|qiong basin show that the natural gas in this reservoir generated in deeper source rock, and migrated to the shallow stratum. The vertical migration distance of most natural gas is more than 2 km.