塔里木盆地库车坳陷天然气气源对比

A gas source study for Kuqa depression of Tarim basin

库车坳陷近年陆续发现了克拉 2号、吐孜洛克、大北 1号、迪那 2号 4个大型气田和依南 2号、依深等天然气藏 ,展示了该区天然气勘探的广阔前景 ,为西气东输战略的顺利实施奠定了物质基础。为判明目前发现的天然气是来源于煤系烃源岩还是来源于湖相泥岩 ,利用苯、甲苯、二甲苯、甲基环己烷等轻烃单体碳同位素等气源对比新技术 ,结合天然气形成的地质背景进行气 源岩的追踪对比。对比结果表明 ,库车坳陷主要气藏的天然气属于煤型气。中、西段克拉苏构造带E、K产层的天然气为高—过成熟煤型气 ;东段依奇克里克侏罗系产层的天然气为成熟—高成熟煤型气 ,吉迪克组产层的天然气为高—过成熟煤型气 ;大宛齐油田上第三系—第四系天然气属成熟—高成熟煤型气。库车坳陷主要气藏的天然气主要来源于侏罗系—三叠系煤系烃源岩。

KaLa 2, Tuziluoke, Dabei 1 and Dina 2 gas fields we re discovered in recent years in Kuqa Foreland basin. In addition, gas pools suc h as Yinan 2 and Yishen were also discovered over there. Discovery of these gas fields brings forth wide foreground of natural gas exploration in this area and provide a solid resources foundation for the strategy of transporting western ga s to east. Kuqa depression develops two kinds of source rock, i.e. lacustrine sh ale as well as coal bearing shale and coal. In order to clarify the natural gas discovered originated from coal bearing source rock or lacustrine shale, new gas source correlation techniques, such as light hydrocarbon monomer carbon isotope s of benzene, toluene, xylene, methylcyclohexane, are applied and combined with g eology condition for the formation of natural gas in this article to carry out g as-source tracing and correlation. Through correlating, it is concluded that na tural gas in main gas pools of Kuqa depression belong to coal-formed gas, natur al gas in E, K pay zone of the middle and west of Kelasu structural belt is high -post mature coal-formed gas; gas in Jurassic pay zone of the east of Yiqikeli structural belt is mature-high mature coal-formed gas, natural gas in the pay zone of Jidike Formation is high-post mature coal-formed gas; natural gas in the Upper Tertiary-Quaternary of Dawanqi oil field belongs to mature-high matu re coal-formed gas; and the natural gas of the main gas pools in Kuqa depressio n mainly originated from Jurassic-Triassic coal-bearing source rocks.