珠江口盆地阳江凹陷中新统潮控体系及其岩性圈闭勘探意义

Miocene Tidal Control System and Its Exploration Significance of Lithologic Trap in Yangjiang Sag,Pearl River Mouth Basin

阳江凹陷作为珠江口盆地西北部浅水边缘盆地珠三坳陷内次级负向构造单元,具有周缘隆起带及局部凸起障壁环境,中新世时期(19.1~13.8 Ma)阳江-一统断裂带两侧火山活动发育,研究区发育港湾状地貌限定下半封闭潮控海岸-河口湾背景.珠三坳陷勘探成熟的多为构造圈闭,而对于岩性圈闭的识别刻画研究尚处在起步阶段,其中阳江凹陷已发现6个含油构造,并部署19口钻井,具有良好的资料基础,中新统缺乏岩性潜力系统研究认识,地层岩性圈闭搜索、排序及优选亟待开展.应用钻测井资料、岩心资料和新采集三维地震资料,基于区域构造-火山活动背景,在高精度层序格架搭建和沉积充填序列框架上,聚焦于阳江凹陷潮控体系沉积特征、沉积相展布及演化规律,进而解剖潮控体系下潮汐砂坝的识别标志、分布规律及岩性圈闭发育特征.研究表明:阳江东凹中新统发育潮控河口湾-潮控三角洲沉积体系,有利岩性圈闭叠合区恩平2-8构造储集砂体为潮汐砂坝,对于珠江口盆地浅水区域潮控体系及岩性圈闭预测具重要理论与勘探意义,并为其他浅水边缘盆地岩性圈闭研究提供了参考借鉴.

Yangjiang sag, as a secondary negative structural unit in Zhu Ⅲ depression, a shallow water marginal basin in the northwest of Pearl River Mouth Basin, has peripheral apophysis belt and local uplift barrier environment. Volcanic activities developed on both sides of Yangjiang-Yitong fault zone during Miocene(19.1-13.8 Ma), developing the background of the semiclosed tidal-controlled coastal-estuary restricted by the harbour geomorphology in the study area. Most of the mature explorations in Zhu Ⅲ depression are structural traps, but the research on the identification and characterization of lithologic traps is still in its infancy. Six oil-bearing structures were found in Yangjiang sag, and 19 wells were deployed, which has a good data base. There is a lack of systematic study on lithologic potential in Miocene series, meanwhile, the search, sorting and optimization of stratigraphic lithologic traps have not been carried out urgently. Moreover, the favorable oil accumulation zones are unknown.Therefore, the research and prediction significance of tidal sand dam are also major feature of this paper. Therefore, based on the regional tectonic volcanic activity background, in this paper, it focuses on the development and sedimentary characteristics of tidal control system, plane distribution and evolution law of sedimentary facies in Yangjiang sag based on the regional tectonic volcanic activity background, focusing on the development and sedimentary characteristics of tidal control system, the plane distribution and evolution of sedimentary facies, and then studies the lithosphere under the tidal control system. At the same time, it is found that several sets of reservoir sandbodies in EP20-8 traps identified in this paper are isolated tidal sand dam. The development and identification of closures, especially the predictive significance of tidal sand dam, are expected to provide reference for the identification and exploration of lithologic traps in shallow water area of Pearl River Mouth basin. It also provides a reference for the study of lithologic traps in other shallow marginal basins.