尼日尔深水区海底扇水道地震形态与迁移历史

Seismic patterns and migration history of submarine fan channel in Niger deep-water area

尼日尔下陆坡深水区的水道发育具多期次特征,内部结构与外形复杂多变,其地理位置与沉积环境不利水道体系的研究.通过地层切片、RMS振幅属性等方法展示不同时间单元水道形态,分析水道体系的期次变换与内部结构的变形过程,探讨水道体系的迁移演化历史.结果表明:中新世中期多发育孤立水道,晚期二级海平面大幅度下降引发大规模浊积事件,促使大量加积式水道形成,在平直处以垂向加积为主,弯曲处呈现垂向加积同时伴随侧向迁移特征.水道演化大致可分为3个阶段:初始侵蚀、切割与充填交替进行、废弃阶段,伴随3个阶段水道弯度发生由中到高再下降的变化.水道的交互式切割与充填基本贯穿第2阶段,切割与充填作为水道弯曲变形一对驱动力,使水道在平面上发生3种迁移方式:侧向摆动、下行迁移、侧向与下行混合迁移.

The channel of deepwater under Niger delta slope is characterized by multi-stage,internal structure and shape variable,its location and sedimentary environment also hinder the research and exploration channel systems.According to strata slicing,RMS amplitude attribute and other techniques,we could exhibit the platforms patterns of channel at different period clearly,and based on the analysis of internal architecture and deformation history of channel-leveed systems,migration and evolution process of channel systems could be understood accurately.A great quantity of isolated channels develop in middle Miocene and aggrading streams in late,generating because of large scale of turbidity caused by the drop of second order sea-level,which characterized by vertical accretion at smooth channel,while vertical accretion and lateral migration at bend.Evolution of channel systems can be divided into three stages: the initial erosion,erosion and filling alternately,and abandoned stage.With these three stages,the sinuosity of channel change from moderate to high,then decrease.Incision and filling of channels,being during the three development phases,is the driving force of meander-loops migration,which promote three kinds of migration patterns: lateral,down-system and combination migration.The research provides theoretical basis for high-precision prediction and evaluation of deepwater reservoir.