塔里木盆地三大构造旋回油气成藏特征

Characteristics of the Hydrocarbon Accumulation Formed Through the Three Structural Cycles in Tarim Basin

塔里木盆地形成经历了南华纪—中泥盆世、晚泥盆世—三叠纪和侏罗纪—第四纪3大伸展-挤压构造旋回,其多旋回构造演化导致油气成藏和分布十分复杂。随着近年来盆地超深层已经成为油田的重点勘探领域,有必要对盆地的油气成藏规律进行深入探讨。本文基于最新的地震资料、钻井资料及油气地质资料,发现塔里木盆地油气规模成藏主力烃源岩为库车地区三叠系—侏罗系及塔西南地区石炭系—二叠系陆相烃源岩、台盆区寒武系海相烃源岩。盆内烃源岩及储盖组合的发育均受控于盆地3大伸展-挤压构造旋回,烃源岩的发育位置决定了塔里木盆地发育库车山前、北部坳陷、麦盖提斜坡及塔西南山前四大含油气系统。盆地在历经3大伸展-挤压旋回,其台盆区、库车前陆及塔西南前陆地区油气成藏组合差异大。台盆区发育石炭系膏泥岩与志留系—石炭系海相砂岩、奥陶系泥岩与灰岩、中寒武统膏盐岩与震旦系—寒武系白云岩储盖组合;库车地区发育新近系—第四系泥岩与砂岩、古近系膏盐层与白垩系砂岩、侏罗系泥岩与三叠系—侏罗系砂岩储盖组合;塔西南地区发育中新统泥岩-砂岩、古近系膏盐层与白垩系砂岩、石炭系—二叠系泥岩与碳酸盐岩储盖组合,分别组成了台盆区、库车及塔西南地区的上部、中部及下部组合。盆内烃源岩在加里东晚期、海西晚期—印支期、喜山期发生排烃,形成三期油气充注,结合塔里木盆地关键变革期的岩性、断裂、不整合及隆起的发育特征,构建了盆地三期成藏模式。

The Tarim Basin was formed through three major extensional-compressional tectonic cycles:Nanhua-Middle Devonian,Late Devonian-Triassic,and Jurassic-Quaternary.This multi-cycle tectonic evolution led to the complexity of the oil and gas accumulation and distribution.In recent years,the ultra-deep layer of the basin has become the key exploration area of oilfield.It is necessary to investigate the hydrocarbon accumulation law of the basin.According to the latest seismic data,drilling data,and oil and gas geological data,we find that the main source rocks of oil and gas accumulation in Tarim Basin are Triassic-Jurassic in the Kuqa area,and the Carboniferous-Permian continental source rocks in southwestern Tarim Basin,the Cambrian marine source rocks in the platform basin area.The development of the source rocks and reservoir-seal assemblages in the basin is controlled by the three major extensional-compressional tectonic cycles of the basin.The development position of the source rocks determines the development of the four petroleum systems in Tarim Basin,including the Kuqa piedmont,northern depression,Maigaiti slope,and southwestern Tarim piedmont.The basin has undergone the three major extensional-compressional cycles,and the hydrocarbon accumulation assemblages in the platform basin area,Kuqa foreland and southwestern Tarim foreland are distinct.The Carboniferous gypsum mudstone and Silurian-Carboniferous marine sandstone,Ordovician mudstone,and limestone,Middle Cambrian gypsum salt rock,and Sinian-Cambrian dolomite reservoir-cap assemblages occur in the basin.The Neogene-Quaternary mudstone and sandstone,Paleogene gypsum salt layer,Cretaceous sandstone reservoir,Jurassic mudstone,and Triassic-Jurassic sandstone reservoir-cap assemblage occur in the Kuqa area.The Miocene mudstone-sandstone,Paleogene gypsum-salt layer,and Cretaceous sandstone,Carboniferous-Permian mudstone and carbonate reservoir-cap assemblages are developed in the southwestern Tarim Basin,which constitute the upper,middle,and lower assemblages of the platform basin,Kuqa and southwestern Tarim Basin,respectively.The hydrocarbon expulsion of the source rocks in the basin occurred in late Caledonian,late Hercynian-Indosinian and Himalayan,forming three stages of oil and gas filling.Combined with the development characteristics of lithology,fracture,unconformity,and uplift in the key transformation period of Tarim Basin,the three-stage accumulation model of the basin is proposed.