深水重力流沉积的层序地层结构与控制因素——南海北部白云深水区重力流沉积层序地层学研究思路

陆架坡折带以外的陆坡深水区陆源碎屑沉积物以深水重力流成因的沉积为主,南海北部陆坡深水区储层研究的主要对象是深水重力流沉积体。在对诸多有关深水沉积和层序地层学经典论著调研的基础上,充分认识深水重力流沉积机理,形成了南海北部白云深水区重力流沉积层序地层学研究的指导思想。深水沉积储层研究应以深水重力流沉积理论为指导,以构建三级层序地层等时格架为基础,以识别共同控制主要深水重力流沉积砂岩储层区域分布的陆架坡折带、三级层序界面、低位体系域等结构单元为研究思路,强调对等时地层结构的解释来远距离预测深水沉积的分布;深水重力流沉积的剖析应充分考虑陆架坡折带以下低位体系域的沉积物来源、输送体系与沉积体的响应关系,进行跨层序界面、跨体系域和穿时性的沉积结构脉络关系研究,即陆架浅海区的前一层序高位体系域沉积物组成,陆坡区层序界面之上的峡谷水道,低位体系域扇体的形态和古沉积地貌等源-沟-扇的沉积结构脉络关系,以及深水扇系统内的沉积体结构响应和过程的研究。

Sequence stratigraphy configuration of deepwater gravity-flow sediments and its controls: a line of thinking in sequence stratigraphy of gravity-flow sediments in Baiyun deepwater area, the northern South China Sea

In the deepwater slope areas beyond the shelf break,terrigenous detrital facies are generally predominated by gravity-flow sediments,and in the deepwater slope area of the northern South China Sea,the main target of reservoir investgation should be sedimentary bodies of gravity flow.Based on analysing many classic papers on the deepwater sediments and their sequence stratigraphy,the sedimentation mechanisms of deepwater gravity flow were deeply understood,and a line of thinking in sequence stratigraphy of gravity-flow sediments was developed in Baiyun deepwater area,the northern South China Sea.Guiding by the theory of deepwater gravity flow and on the basis of building a three-order isochronous sequence framework,the shelf break belt,the third order of sequence boundary and the lowstand system tract,which commonly controlled the regional distribution of deepwater gravity-flow sandstone reservoirs,are recognized,and it is emphasized to remotely predict deepwater deposition by explaining the isochronous stratigraphic configuration.For the analysis of deepwater gravity-flow sediments,the sediment sources and the responce relationship between transportation systems and sedimentary bodies should be fully considered in the lowstand system tracts below the shelf break belt,and the relationships in sedimentary configuration should be researched across sequence boundaries,across system tracts and diachroniclly,including the sediment composition of pre-sequence highstand system tracts in the shallow shelf area,the source-channel-fan relationships among the canyons,the lowstand system tract fans and the depositional plaeo-geomorphology on the sequence boundaries in the slope area,and the response and process of sedimentary configuration into deepwater fans.