孟加拉扇某区块地层层序划分及典型地震相识别

研究区位于孟加拉扇某区块水深大于2000m的陆坡深水区,区内缺乏典型的层序地层界面。该文以层序地层学理论为指导,通过地震属性、分频、地震相等分析,开展了层序地层划分及沉积体的识别。依据深水沉积旋回在地震剖面上振幅特征的变化,进行了层序界面的识别,进而在等时层序地层格架内研究地震相及沉积相的分布特征,参考深水沉积相发育模式,并结合"U"形相、丘状相、强振幅平行相、中弱振幅平行相以及透明杂乱反射相等5种典型地震相的外部形态、发育位置等,认为各地震相分别对应水道、水道堤岸、浊积朵体、深海泥岩以及块状搬运复合体等沉积单元,并指出典型地震相的分布特征,可辅助地层层序的划分。

Sequence stratigraphy and typical seismic facies in one exploration block of Bengal Fan

The study area is located in the deep-water area,with water depth beneath 2 000 m,so it is difficult to recognize the sequence boundary with the seismic termination.Based on sequence stratigraphy theory,seismic facies combining with seismic attribute and frequency division are applied to carry out the sequence stratigraphy division and deposition identification.According to the amplitude characteristics of deep water sedimentary cycles on seismic profiles,the sequence boundaries are identified.LST and T-HST developed in each third-order sequence.Characteristics of the seismic facies and the sedimentary facies are analyzed in the equitime sequence framework.Referred to the sedimentary facies model in the deep water,and integrated with the external configuration and the localization of the five typical seismic facies,it is regarded that the U-shaped facies,dome-shaped facies,parallel seismic facies with high amplitude,parallel seismic facies with mid-low amplitude and transparent and chaotic reflecting facies are respectively on behalf of incised channel,channel-levee complex,turbidite lobes,deep-water mudstone and mass-transport deposits.The distribution characteristics of the typical seismic facies are helpful to the recognition ofthe sequence boundaries.