坡折带对陆相湖盆辫状三角洲层序和沉积的控制——以准噶尔盆地东缘三工河组为例

Controls of the structural slope breaks on the braided delta sequences and sedimentary facies in continental lake basins: An example from the Sangonghe Formation in the eastern Junggar Basin, Xinjiang

关键词:  坡折带  辫状河三角洲  准噶尔盆地东缘  三工河组  沉积微相组合

Key words:  slope break  braided delta  eastern Junggar Basin  Sangonghe Formation  sedimentary microfacies association

摘要:

通过对钻探、地震及露头资料的研究,将准噶尔盆地东缘三工河组划分为两个三级层序。在地震和测井剖面上识别出挠曲坡折带和断裂坡折带两种构造坡折带。坡折带对于研究区层序和沉积的控制作用主要表现为:对于层序,"径向沟梁辐射,纬向阶梯分布"的坡折带体系使得本区三工河底部低水位体系域发育,坡折带加强河道侧向迁移,削弱河道下蚀,增加准层序数量,坡折带高部位低水位体系域会侵蚀下覆地层;对于沉积,在精细开发区的三工河组识别出6种沉积微相组合,顺物源连井剖面上自下而上识别出3个沉积微相组合序列,陡坡区发育富河口坝三角洲前缘,缓坡区发育富河道三角洲前缘。

Abstract:

The Sangonghe Formation on the eastern margin of the Junggar Basin, Xinjiang is divided, on the basis of cores, seismic data and well logs, into two third-order sequences J₁ SQ1 and J₁ SQ2, each of which may be involved into the lowstand, transgressive and highstand systems tracts. Two types of slope breaks are recognized in the seismic profiles and well-tie sections, including the textural and faulted slope breaks. The slope break system distributed in radial and latitudinal directions led to the development of the lowstand systems tract at the base of the Sangonghe Formation. Six sedimentary microfacies associations are arranged into three sedimentary microfacies association sequences in the Sangonghe Formation. The slope breaks in the steep slope zones are significant in that they may facilitate the development of the lowstand systems tract, in which the channel-mouth bar delta front sandstones in the steep slope zones are interpreted as the favourable areas for hydrocarbon accumulation.