南海北部莺歌海盆地东方区上新统侧积复合体沉积特征及成因

Sedimentary characteristics and genesis of lateral accretion packages in the Pliocene of Dongfang area of Yinggehai Basin in northern South China Sea

基于三维地震数据的剖面、切片和属性解释,在南海北部莺歌海盆地东方1-1地区发现一种特殊类型的沉积体。按照侧积复合体弯曲度大小可分为高弯度型和低弯度型两类,在地震剖面上均以叠瓦状强振幅反射为主要识别标志,不同之处是前者在平面上通常呈一组同心半环,后者则表现为带状展布。侧积复合体可能为重力流水道多期"下切—充填"并发生连续横向迁移而成,其下部由互相切叠的水道底部沉积组成,一般粒度较粗且横向连续性好,可作为良好的油气储集层;而向上变为砂泥间互的岩性组合,连通性减弱、储集性能降低。侧积复合体的发现对深水重力流沉积体系研究具有重要意义,且可为研究区的油气勘探提供新的远景目标。

Based on the interpretation of seismic profiles, slices and attributes, lateral accretion packages （LAPs） were found in Dongfang 1-1 area of the Yinggehai Basin in northern South China Sea.According to their sinuosity, LAPs can be categorized into high or low sinuous types, which are both characterized by a series of shingled reflections on seismic profiles. However, in the plan view, the high sinuous type is represented by a scroll-bar pattern while the low sinuous type is ribbon-like. The LAPs are suggested to be formed by multiple stages of ＂ cut-fill＂ as well as the subsequent lateral migration. The lower part of LAPs are consisted of coarse-grained reservoir resulting from the amalgamation of channel axis bottom deposits, which have good lateral connectivity and reservoir potential. However, it turns upwards into the combination of sandstones interbeded with mudstones, leading to a low lateral connectivity and quality. The discovery of the LAPs is significant to understand the nature of the deep-water gravity-flow systems and also provides potential targets for the hydrocarbon exploration in the study area.