新疆东部三塘湖盆地构造演化及其石油地质意义

Tectonic Evolution of the Santanghu Basin,East Xinjiang and Its Implication for the Hydrocarbon Accumulation

三塘湖盆地形成于晚古生代以后 ,是一个构造演化复杂的中小型含油气盆地 ,经历了石炭纪到早二叠世盆地基底形成阶段、晚二叠世到白垩纪盆地发育阶段和第三纪以来的后期盆地改造阶段。在基底形成阶段 ,早石炭世为古准噶尔洋盆俯冲的活动大陆边缘时期 ,晚石炭世进入哈萨克斯坦板块和西伯利亚板块碰撞造山时期 ,早二叠世为碰撞后伸展转换时期。从晚二叠世以后 ,盆地进入发育阶段。晚二叠世为造山后伸展断陷时期 ,三叠纪末为挤压隆升时期 ,侏罗纪—早白垩世盆地进入凹陷时期 ,早白垩世末期为挤压逆冲时期。从第三纪以来 ,盆地进入了后期的改造阶段。在整个盆地演化过程中 ,晚二叠世盆地处于张性成盆环境 ,并沉积发育了上二叠统芦草沟组泥灰岩、上三叠统小泉沟群和下—中侏罗统水西沟群以暗色泥岩为主的三套烃源岩。受其区域性挤压构造背景影响 ,早白垩世末期和晚始新世是盆地两个油气成藏关键时刻 ,特别是新生代晚期盆地的改造对油气能否进入成熟生油阶段具有重要意义。

The Santanghu Basin is a middle-minor scale petroleum basin whose tectonic evolution has been very complex since late Paleozoic.Its evolutional history can be divided into three stages:formation of basement during Carboniferous to early Permian,development during late Permian to Cretaceous and reconstruction since Tertiary.It was an active continent margin in early Carboniferous when ancient Junggar oceanic basin was subducting to north.By the late Carboniferous time a collision occurred between the kazakhstanian plate and the Siberian plate.It was in a tectonic transform phase from collisional compression to post-collisional extension in early Permian.The Basin came into development stage during late Permian to Cretaceous including the extension and fault period of post-orogeny in late Permian,the compression and uplift period at end of Triassic,the extension and depression period from Jurassic to early Cretaceous,and the compression and thrust period at the end of early Cretaceous.During its tectonic evolution,the Santanghu Basin was in extensional setting in late Permian,in which three sets of hydrocarbon source rocks deposited.They are the Lucaogou Formation of upper Permian,the Xiaoquangou Group of upper Triassic and Shuixigou Group of the lower-middle Jurassic,which are dominated by dark mudstone.The end of early Cretaceous and the late Eocene are two critical moments of the reservoir generation and accumulation in the Santanghu Basin due to the control of regional tectonic compression.Especially the reconstruction during the Late Cenozoic is of far reaching importance for whether the petroleum can enter into mature oil-generating stage or not.