中国典型叠合盆地油气成藏研究新进展(之二)——以塔里木盆地为例

近年来,中国西部典型叠合盆地油气成藏研究获得重大进展。成盆方面:1)地球物理综合剖面揭示了塔里木盆地与天山造山带的深、浅层耦合特征具有走向分段性,大致以羊布拉克为界,以东表现为近东西向斜向伸展的特征;以西,主要表现为近南北向垂直于地层走向的伸展状态;2)揭示了塔里木盆地的翘倾式叠合演化的特点,自寒武纪到第四纪,盆地沉降中心经历了由东向西向周缘的迁移过程。成烃方面:1)建立了海相碳酸盐岩优质烃源岩发育的环境指标及发育的盆地类型,高丰度烃源岩仅发育于被动大陆边缘背景下的裂谷、克拉通内坳陷盆地和活动大陆边缘背景下的前缘斜坡、挠曲类前陆坳陷中;2)确立了有效碳酸盐岩烃源岩的有机质丰度下限为0.25%～0.30%。成藏方面:1)轮南地区早古生代碳酸盐岩储层中发育3期烃类包裹体,与区域性油气充注事件有关,分别形成于晚志留世—早泥盆世、晚白垩世及新近纪;2)通过油源对比分析,指出轮南、塔河地区的原油可能源于中、上奥陶统源岩;3)同位素示踪研究及包裹体测温揭示了塔中地区流体具有深部来源特征。而且,萤石交代灰岩对储层物性具有显著改善作用。并指出塔里木盆地近期油气勘探中,在台盆区碳酸盐岩勘探领域不断有新层系和新类型油气的发现,台盆区碎屑岩勘探领域于志留系和泥盆系也连获突破,展示了塔里木盆地良好的勘探前景。

New progresses in research of China's typical superimposed basins and reservoiring of hydrocarbons (Part Ⅱ ):taking Tarim basin as an example

Research of reservoiring in typical superimposed basins in China has made great progresses in recent years.In respect of basin formation:(1) Composite geophysical profiles reveal that the coupling of shallow and deep layers in Tarim basin and Tianshan orogenic belt is characterized by segmentation along strike.It appears as near E-W trending oblique extensional features to the east of Yangbulake,and near S-N trending extensional features vertical to the strike of strata.(2) The evolution of Tarim basin is characterized by tilting superimposition,i.e.from Cambrian to Quaternary,the depocenter migrated from the east to the west and finally to the periphery area.In respect of hydrocarbon generation:(1) Environmental indexes and basin types for development of good marine carbonate source rocks have been established.Source rocks with high abundance of organic matter have only been developed in rift valleys of passive continental margin,intra-cratonic down-warped basins,and frontal slopes and flexured foreland depressions in active continental margin.(2) The lower limit of organic matter abundance for effective carbonate source rocks has been determined to be 0.25%-0.30%.In respect of reservoiring:(1) Hydrocarbon inclusions in the Lower Paleozoic carbonate reservoirs in Lunnan area have been formed in Late Silurian-Early Devonian,Late Cretaceous and Neogene,respectively,and they are related with regional charging events of hydrocarbons.(2) Oil-source correlation shows that the oil in Lunnan and Tahe might have been sourced from the Middle-Upper Ordovician source rocks.(3) Isotope tracer study and temperature measurement of inclusions show that the fluids in Tazhong have deep source characteristics.Moreover,fluorite replaces limestone would have greatly improved the poroperm characteristics of the reservoirs. The discoveries in new series of strata and new type discoveries obtained in exploration of carbonates in Paleozoic craton area,as well as the breakthroughs got in exploration of Silurian and Devonian clastic rocks in Paleozoic craton area,show that Tarim basin has large exploration potentials.