大坎波斯盆地盐构造变形及其对盐上层系油气成藏的控制

    Salt structural deformation and its control over hydrocarbon accumulation of post salt layer system in the Great Campos Basin

    • 摘要: 大坎波斯盆地是一个含盐岩的富油气盆地,其盐下层系近年来获得了重大发现,而盐上层系则处于勘探低谷。为了明确盐上层系的勘探潜力,系统分析了盐构造变形对盐上层系地层结构、沉积演化和油气成藏的控制作用。结果表明,受盐构造变形控制,盐上层系由西向东发育滑脱盐筏带、底辟盐脊带和推覆盐墙带。盐构造变形限制和改造了盐上层系深水沉积,早期的盐构造变形一般对晚期的深水沉积起到溢出、导向和遮挡等局限作用,晚期的盐构造变形一般对早期的深水沉积起到底辟和截切等改造作用。盐构造变形为盐上层系油气成藏提供了圈闭和运移通道。滑脱盐筏带一般发育与盐岩滚动相关的构造-地层圈闭,主要包括滚动背斜圈闭、地层尖灭型圈闭和断层阻挡型圈闭;底辟盐脊带主要发育与盐岩上拱相关的构造圈闭,如盐顶背斜圈闭、盐侧翼遮挡圈闭和龟背斜圈闭。盐窗与长期处于开启状态的盐相关断层构成了油气运移的优势通道。该研究成果对指导大坎波斯盆地下步油气勘探具有重要参考价值。

       

      Abstract: The Great Campos Basin is a salt rich oil and gas basin, with significant discoveries made in recent years in the pre salt layers, while the post salt layers are in a low exploration valley. In order to clarify the remaining exploration potential of the post salt strata in the Great Campos Basin, a systematic analysis was conducted on the control effect of salt structural deformation on the stratigraphic structure, sedimentary evolution, and hydrocarbon accumulation of the post salt strata. The results are as follows. Under the control of salt tectonic deformation, the post salt layers develop detachment salt raft zone, diapir salt ridge zone, and nappe salt wall zone from west to east. The deformation of salt structures has restricted and transformed the deep water sedimentation of the post salt drift strata. Early salt structure deformation generally plays a limiting role in overflow, guidance, and shielding of late deep-water sedimentation, while late salt structure deformation generally plays a transformation role in diapir and cutting of early deep-water sedimentation. The deformation of salt structure provides traps and migration pathways for the hydrocarbon accumulation in post salt strata. Tectonic stratigraphic traps related to salt rock roll are generally developed in the detachment salt raft belt, mainly including Rollover anticlines traps, stratum pinch out traps and fault block traps; The diapir salt ridge zone mainly develops structural traps related to salt rock diapirs, such as salt top anticline traps, salt flank barrier traps, and turtle back anticline traps. Salt windows and salt related faults that have been in an open state for a long time constitute the dominant channels for oil and gas migration.This research achievement has important reference value for guiding the next oil and gas exploration in the Great Campos Basin.

       

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