南海西北次海盆物源供给模式及油气勘探前景

Provenance Supply Model and Exploration Prospect of the Northwestern Sub-Basin, South China Sea

基于地震资料,从物源供给模式入手,分析南海北部深水区西北次海盆的沉积层序、物源特征及其油气勘探前景。其物源供给具有相对多期多物源体系特征,初始扩张期沉积中心位于盆地北部边缘,北部陆架-陆坡物源体系作用显著;初始热沉降期,沉积中心开始从盆地边缘向中央转移,北部陆架-陆坡、中-西沙隆起区物源体系具有大规模物源供给,在盆地两侧斜坡坡脚对称发育大量具有下超反射特征的裙积扇以及具有杂乱反射特征的块体搬运沉积体;稳定热沉降期,沉积中心转移至盆地中央,北部陆架-陆坡、西沙海槽物源体系作用存在短期明显加强,中-西沙隆起区物源体系逐渐削弱,盆地内发育大规模深水扇及深水水道。与相邻中—高勘探程度区相比,显示出良好的勘探潜力。

Based on the existing high-resolution 2D seismic data and provenance supply mode, the depositional sequence, provenance features and oil-gas exploration prospects were analyzed. The provenance supply is characterized by multiple provenances. During initial expanding period, the depocenter was located at the northern margin of the basin and the north shelf-slope provenance system played an important role. In the initial period of thermal subsidence, the depocenter started to migrate to the center from the margin of basin, the north shelf-slope and Zhong-Xisha uplift zone provenance systems possess mass sediment supply. The two slope-apron fans with downlap characteristics and mass transport depositions with chaotic reflections were symmetrically growing in the north-south sides. In the stable thermal subsidence period, the depocenter has moved to the center, the contribution of North Shelf-Slope and Xisha trough provenance systems was reinforced in the short term and produced a large-scale deepwater fan and deepwater channel system, while the Zhong-Xisha uplift provenance system was weakened. Large scale deepwater fans and channels were developed within the basin. Compared with neighboring areas with middle-high exploration level, the study area shows a promising exploration targets.