孟加拉扇上扇某区块深水沉积体的特征及演化模式

利用高分辨率三维地震资料分析了孟加拉扇上扇某区块的深水沉积体特征。发现了六种典型地震相:下切充填相、海鸥翼状相、楔形发散相、透明相、强振幅平行相和弱振幅平行相。下切充填相代表粗粒的水道充填沉积；海鸥翼状相代表水道-天然堤复合体；楔形发散相代表细粒的天然堤沉积；透明相代表块体搬运沉积；强振幅平行相代表朵叶体沉积；弱振幅平行相代表深海披覆沉积。通过对典型地震剖面特征和平面属性分布分析可知:上扇垂向上依次沉积了朵叶体、水道和堤岸、朵叶体、水道-天然堤复合体。

The Architecture and Evolution of Deepwater Sedimentary Elements in One Study Area within Upper Bengal Fan

Like Amaon fan and Mississippi fan,Bengal fan is a favorable field for investigating sedimentary process in deepwater.Considering lacking coring and well data,high-resolution 3D seismic data from the study area was analyzed to study the architecture and evolution of sedimentary elements on the upper Bengal Fan.the area of interest belonged to deep-water region,and stratigraphy was formed in marine deposition.Six typical seismic facies have been identified,which were incised channel fill facies,gull wing-shaped facies,wedge-shaped divergent facies,transparent facies,high-amplitude parallel facies and low-amplitude parallel facies.Seismic Facies 1 was interpreted as coarse-grained deposits of abandoned channels.Seismic Facies 2 represented channel-levee complex.Seismic Facies 3 was interpreted as fine-grained levee sediments.Seismic Facies 4 represented mass transport deposits.Seismic Facies 5 was interpreted as lobes,which was different from sheet sand interpreted by predecessors.Seismic Facies 6 represented hemipelagic drapes and fills.On seismic profile lobex and channels display high amplitude,which means coarse lithology deposition,and may be good reservoirs.Through analysis of S-N and E-W seismic profiles reflection charateristics,seismic attribute planeform,we revealed the sedimentary evolution: during the period of SQ1,lobes were deposited,and turbidute flow tansported sediments far into basin;main deep-water elements of SQ2 were channels and levees,with channel migrating from SE to NW;Sedimentary elements of SQ3 were lobes,locally MTDs originated from slides,slumps and debris flow;channel-leveed complex mainly dominated the stratigraphy of SQ4.