准噶尔叠合盆地复式油气成藏规律

Characteristics of composite hydrocarbon accumulation in a superimposed basin,Junggar Basin

准噶尔盆地是中国西部重要的含油气叠合盆地,近50年来的油气勘探开发不断取得突破,是叠合盆地复式油气成藏的一个典型实例。基于准噶尔盆地最新勘探发现和已有研究认识,文章总结了油气成藏规律,分析了重大勘探领域,以此为勘探战略选区提供依据,丰富和发展陆相石油地质理论。结果表明,准噶尔多期盆地类型叠加演化过程中,纵向上形成了"三层楼"成藏组合;横向上不同时期、不同地区、不同规模的隆、坳构造格局相互叠置,多期叠合的改造形式和强度,形成了不同地区不同的地质结构,决定了油气聚集与分布具有地区差异性。油气富集规律表现为烃源岩对油气分布具有首要控制作用;盖层、断裂、古构造、不整合以及沉积相对油气的分布具有次级控制作用。盆地富烃凹陷斜坡区中深层-深层、南缘冲断带、陆梁隆起石炭系以及中-下二叠统页岩油(气)等领域是未来风险勘探部署有望获得战略突破的现实领域。准噶尔叠合盆地多旋回构造演化的性质,决定了这类盆地勘探的长期性和油气发现的多阶段性。

The Junggar Basin is one of the most important petroliferous superimposed basins in western China.Oil and gas discoveries made there in recent decades have confirmed its great hydrocarbon potential as a superimposed basin.Data gathered through the latest exploration breakthroughs and previous studies are used to summarize the enrichment patterns of oil and gas,analyze the characteristics of oil and gas discoveries,guide strategic selection of exploration targets,and provide theorical materials for a geological study on continental petroleum reservoirs in the basin.The result shows that the reservoir assemblages in the basin exhibit a vertical“three-story”pattern and horizontal superimposition of uplifts and depressions of different stages,areas and scales in various patterns and intensity during the multi-stage superimposition process,which results in a disparity in the accumulation and distribution of oil and gas.It also suggests that the oil and gas distribution is controlled firstly by source rocks and secondly by caprocks,faults,paleo-structures,unconformities and sedimentary facies.Four major strategic exploration targets are singled out:the mid-deep to deep layers in slope area of hydrocarbon-rich sag,the thrust belt of the southern margin,the Carboniferous of Lu-Liang uplift,and shale oil in the Middle-Lower Permian.However,finding oil and gas reservoirs in this multi-cycle tectonic basin is still a big challenge due to its complex evolution history.