珠江口盆地恩平凹陷北带下-中中新统层序构型及其差异性分析:对岩性圈闭发育的启示

针对海相三角洲层序地层研究中的理论和应用问题，选取珠江口盆地恩平凹陷北带下-中中新统（T50-T35）古珠江三角洲为目标开展了精细解剖.在消化吸收“沉积层序”理论最新进展的基础上，结合古珠江三角洲发育特点和井震资料条件，提出了基于层序界面（SB）、最大海退面（MRS）、最大海泛面（MFS）和高频海泛面（FS）等4种类型界面的高频层序划分方案，划分结果具有旋回特征明显、界面特征统一等优点，并揭示了研究区低位体系域较为发育的重要特征.在高精度层序格架约束下，进一步采用地震沉积学技术开展了精细沉积剖析，结果显示研究区低位域以大型交切状辫状水道为主，砂体厚度大且连片分布；相比而言，海侵、高位体系域含砂率明显变低，以弯曲、低能河道或滨岸-沿岸坝体为主，具备更大的岩性圈闭潜力.此外，结合层序构型分类的结果，提出以A型层序构型（高位域占比大）为主的韩江组六段和珠江组一段具备较大的岩性圈闭潜力.相关结论对珠江口盆地和其他海相盆地岩性圈闭勘探具有一定指导意义. 

Variability in Sequence Stratigraphic Architectures of Lower-Middle Miocene Pearl River Delta,Northern Enping Sag,Pearl River Mouth Basin: Implications for Lithological Trap Development

In view of the theory and application of sequence stratigraphy in the marine deltaic facies, in this paper it selects the Lower-Middle Miocene (T50-T35) acient Pearl River delta in the north of the Enping sag, Pearl River Mouth basin as the target to carry out detailed anatomy. On the basis of digesting and absorbing the latest development of "depositional sequence" theory, combined with the development characteristics of ancient Pearl River delta and well seismic data conditions, a high-frequency sequence stratigraphic scheme is proposed on the basis of four types of surfaces, namely the sequence boundary (SB), maximum regressive surface (MRS), maximum flooding surface (MFS) and high-order flooding surface (FS). The results reveal that the most striking feature of the sequence stratigraphy of this area is the extensive development of the lowstand systems tracts. Constrained by the high-resolution sequence framework, the seismic sedimentology technology is further used to carry out the fine sedimentary analysis. The results show that the lowstand systems tracts in the study area are mainly composed of large intersecting braided channels, with large thickness and continuous distribution of sand bodies. In contrast, the sand content of transgressive and highstand systems tracts is obviously lower, with sinuous, low-energy river channel or shore-parallel bars as the main body, signifying greater lithologic traps potential. In addition, combined with the results of sequence architecture classification, it is proposed that the sixth member of Hanjiang Formation and the first member of Zhujiang Formation, which are dominated by A-type sequence architecture (highstand systems tracts dominated), have great lithologic trap potential. The conclusions of this study have certain guiding significance for the exploration of lithologic traps in the Pearl River Mouth basin and other marine basins.