西非盐下裂谷构造特征及其地质意义

    STRUCTURAL CHARACTERISTICS OF WEST AFRICA IN PRE-SALT RIFT STAGE AND THEIR GEOLOGICAL SIGNIFICANCE

    • 摘要: 西非海岸盆地盐下裂谷随着近年来油气新发现显示出巨大的勘探潜力。基于区域地震资料,对盐下裂谷构造层系开展解释,并对裂谷构造特征开展了深入探讨。研究表明,西非盐下盆地具有早期裂陷、晚期坳陷的构造特征。平面上具有内裂谷带—中央隆起带—外裂谷带东西向隆坳相间的一级构造格局,在外裂谷带又识别出了一系列凸起和凹陷二级构造单元。裂谷隆坳格局受断层控制,具有“东西分带、南北分段”的平面特征。裂谷期构造特征指示出西非陆内裂谷作用发生具有北早南晚、持续时间北长南短板块构造意义。同时裂谷演化过程中衍生重要的含油气系统,具有重要的油气勘探意义。

       

      Abstract: Recent hydrocarbon discoveries have proved that the pre-salt rift stage of the West Africa coastal basin has great oil and gas potential. Based on the data from the regional seismic surveys, this paper made a detailed study on the structural patterns of pre-salt rift. It shows that the pre-salt rift in West Africa is composed of two stages: early rift stage and later depression stage. On the plane, several first-order tectonic units, such as the Inner sub-basin, the Central uplift and the Outer sub-basin, are identified. Within the outer sub-basin, there occur alternated secondary tectonic units, which includes uplifts and depressions under the control of faulting and the pattern of east-west zonation and north-south segmentation are rather clear. The structural patterns of pre-salt rift stage indicate that the rifting started earlier and lasted longer in the north comparing to the south. The evolution of rifting has great significance to the generation of petroleum system and the pre-salt-rift stage is a favorable target for hydrocarbon exploration.

       

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