南海北部陆缘古近系沉积相演化及深水陆坡油气前景分析

Study on the Evolution of Sedimentary Phases at Paleocene and Exploration Prospect at Deepwater of Slope in the Northern South China Sea

浅水陆架区的油气勘探成果表明,古近系是南海北部陆缘裂陷期的沉积产物,是重要的烃源岩层系。但由于水深及勘探技术等多种因素的制约,南海北部陆缘深水陆坡区的勘探程度及地质综合研究程度非常低,对古近系地层的沉积相演化及分布情况缺乏认识。本文通过最新深水陆坡区的地震剖面解释资料以及前人浅水陆架区的沉积相研究资料,结合南海新生代以来的构造运动及演化特征分析,对南海北部陆缘古近系的沉积相演化及分布特征进行研究,认为南海北部陆缘古近系的沉积相演化过程反映了一个从冲积相–河流三角洲相–湖相–滨浅海相–半深海相由陆向海的陆缘断陷伸展演化过程,深水陆坡区和浅水陆架区沉积相演化背景相同,亦分布着巨厚的古近系地层,存在良好的烃源岩层系,未来深水陆坡区存在广阔的油气勘探前景。

The results of oil and gas exploration indicate that the Paleocene of the continental margin in northern South China Sea,deposited during the rifting stage,is important source rocks.However,due to the restriction of deep water and exploration technology,the level of exploration and geo-logical comprehensive study is very low,especially lacks understanding on the evolution and dis-tribution of the Paleocene among the deepwater slope of northern South China Sea.Based on the seismic data interpretation and the predecessors’research data of deposition in the shelf area of shallow water,and the study of the tectonic movement and evolution of sedimentary since Cenozoic,the author proposes that the process of deposition evolution indicates the rift-stretching evolution from the phase of alluvial to phase of river delta to phase of lake-phase of foreshore the shallow water of sea-phase of half of the deepwater sea,that is the process from the phase of land to the phase of sea.As same as the tectonic background of the sedimentary evolution of the shallow water shelf area,thick source rocks of the Paleocene are largely distributed and there’s good exploration prospect of oil-gas in deepwater slope of northern South China Sea.