东非裂谷系西支先存构造调节带构造特征及其与油气成藏的关系

The Research on the Structural Features of Pre-existing Tectonic Accommodation Zones and the Relationship with Hydrocarbon Accumulation in the Western Branch of EARS

近年来,随着东非裂谷系盆地油气勘探不断突破,成为倍受世界关注的研究中心。但同时由于其勘探研究程度极低,对这种世界最年轻裂谷盆地的成烃、成藏机制一直是令人困惑的问题。笔者通过地球物理资料结合区域地质资料的综合研究,深入解剖该区构造特征及其成因演化机制,分析构造与成藏的根本控制作用,研究认为裂谷系西支盆地是在先存构造控制下发育起来的洼陷与调节带相间的辫状构造集合体,从北向南推土机式继承、连续开裂。而先存古洼为有效烃源母质的发育提供了优越的环境与雄厚的物质基础,先存构造调节带在热点的持续作用下则为河流三角洲的发育、断裂和构造圈闭的形成提供了有利的场所。同时,先存构造调节带控制了油气运移的优势方向和油气运移疏导体系,建立了本区先存构造调节带连锁控藏的油气成藏模式。通过上述研究,指出长轴缓坡构造调节带是裂谷西支盆地最有利的勘探方向。

In recent years,with the large oil&gas fields discovered,EARS has become a research center received worldwide attention.But at the same time,due to the extremely low level of the research and exploration,the formation mechanism of source rocks and oil&gas accumulation in the youngest rift basin in the world has always been a confusing problem.Through the comprehensive study of geophysical data combined with regional geological data,the author deeply dissected the structural features of the area and its evolution mechanism,and analyzed the fundamental control of tectonic and hydrocarbon accumulation.The study has concluded that the western branch of EARS is the braided tectonic aggregates between the depression and the accommodation zones under the control of pre-existing structure,evolution from north to south is series.Paleo depressions provided the quality environment and enough sediments for the development of source rocks,and pre-existing tectonic accommodation zones provided the advantageous locations for the development of deltas and the formation of fractures and structure traps.At the same time,the pre-existing tectonic accommodation zone controls the dominant direction and the drainage system of hydrocarbon migration.And the hydrocarbon accumulation model controlled by the pre-existing tectonic accommodation zone has been established.Through the above research,it is pointed out that the long axis gentle slope of tectonic accommodation zone is the most favorable exploration direction of the western branch of EARS.