川东北地区飞仙关组-长兴组天然气富集机制

摘要

In Northeast Sichuan Basin,the accumulation elements of different areas of Feixianguan-Changxing Formations are the same,but the enriched degrees of the nature gas vary from region to region.In order to dis-closure the enriched mechanism of the nature gas,this paper analyzed the origin of the nature gas in Feixian-guan-Changxing Formations,the hydrocarbon generating density of main resource rocks,the characteristics and the scales of the reservoirs,the conservation condition of the natural gas,the history of hydrocarbon generation and the adjusting process of the oil and gas reservoirs with the analyzed and examined data of resource rocks, the data of the cores and lamellas,and the data of the well logging and cutting logging,etc.Results show that:(1 )the Northeast Sichuan Basin is in the center of hydrocarbon generation or its vicinity ,and the primary mi-gration distances of the oil and gas are short;(2)the lithologic gas reservoirs of reefs and sands are independ-ent,and the distribution of the reservoirs controls the scales of the oil and gas reservoirs;(3 )several gypsum mantles cover the natural gas reservoirs and the conservation condition of the natural gas is good;(4)the high temperature made the early oil reservoirs cracked to the present gas reservoirs;(5 )with the tectonic movement, the accumulating processes of gas are separated into three steps,the formation of the early oil reservoirs,the cracking of the early oil reservoirs with the formation of the gas reservoirs and the formation of the present gas reservoirs.Discussing the enrichment mechanism of natural gas is useful for finding the beneficial target areas in the Northeast Sichuan Basin when natural gas is explored.%飞仙关组-长兴组气藏在川东北不同地区成藏要素基本相同，但是区域上天然气富集程度有所不同。为了揭示天然气的富集机制，通过烃源岩分析测试资料、岩心和薄片观察资料、测井和岩屑录井资料等，分析了川东北地区飞仙关组-长兴组天然气的来源、主力烃源岩生烃强度、储层性质与规模、天然气的保存条件、生烃演化史和油气藏的调整过程。研究表明：（1）川东北地区处于或邻近生烃中心，油气初次运移距离短；（2）礁滩岩性气藏相对独立，礁滩储层分布范围控制着古油藏的规模；（3）气藏上覆多套膏盐岩盖层，天然气保存条件好；（4）早期的古油藏经历高温已经全部裂解，形成现今的气藏；在构造作用控制下，天然气聚集成藏经历了古油藏的形成、古油藏裂解及古气藏的形成和现今气藏的形成3个阶段。对川东北天然气富集机制的探讨，有助于进一步寻找有利靶区，指导天然气勘探。