Abstract: Doseo Basin, located within the Central African Rift System, is a key frontier for onshore oil and gas exploration in Africa. Based on comprehensive analysis of geological structure, as well as sedimentary and hydrocarbon systems, this study systematically explores the multi-phase evolution of strike-slip faulting and the characteristics of the regional tectonic stress field in Doseo Basin. Combined with an analysis of hydrocarbon accumulation conditions in the basin, the study reveals the controlling mechanisms of strike-slip structures on hydrocarbon accumulation. The results show as follows. (1) The tectonic evolution of Doseo Basin is controlled by the sustained dextral activity along the Central African Shear Zone. Extension and strike-slip tectonism occurred during the Early Cretaceous, followed by compression and strike-slip tectonism during the Paleogene. The superimposition of multiple-phase strike-slip tectonism resulted in the formation of complex flower-shaped structures within the basin. (2) In the Early Cretaceous, extension and strike-slip tectonism led to the development of deep and steep depressions along pre-existing NEE-trending faults in the northern part of the basin, where nearly one-kilometer-thick organic-rich mudstone was deposited under warm and humid climatic conditions. At the same time, strike-slip transition zones at the basin margins provided sediment pathways, facilitating the development of shallow-water/braided river deltas and fan delta front sand bodies in the southeastern and northern parts of the basin, respectively. These sand bodies, in conjunction with the mudstones in the depressions, formed high-quality reservoir-cap assemblages. (3) The Late Paleogene compression and strike-slip tectonism controlled the development of NE-SW trending structural ridges, forming numerous faulted anticlines and plunging anticline traps. This phase coincided with the second stage of hydrocarbon charging and played a key role in controlling hydrocarbon accumulation and distribution. (4) The hydrocarbon accumulation model of Doseo Basin was clarified. Specifically, hydrocarbon accumulation is controlled by the presence of high-quality reservoirs in the northern steep slope zone, the fault and overburden caprock configurations in the central strike-slip fault zone, and stable caprock seals and favorable preservation conditions in the southern slope zone. The research results provide crucial insights for hydrocarbon exploration in the strike-slip tectonic zones of Doseo Basin.

Key words: Central African Rift System, Doseo Basin, multi-phase strike-slip structures, extension and strike-slip, compression and strike-slip, hydrocarbon accumulation

摘要： 中非裂谷系的Doseo盆地是非洲大陆上重要的油气勘探前沿地区。基于构造解析以及沉积和油气系统等资料,系统分析了Doseo盆地的多期走滑构造演化史和区域构造应力场特征,并结合盆地油气成藏条件,揭示了走滑构造对油气成藏的控制机制。研究结果表明:(1)Doseo盆地的构造演化受中非剪切带的持续右旋活动控制,早白垩世发生了伸展-走滑构造运动,古近纪发生了挤压-走滑构造运动,多期走滑构造作用叠加形成了盆地内的复合花状构造;(2)早白垩世,伸展-走滑构造作用使得盆地北部沿NEE向先存断裂形成深陡凹陷,盆地在温湿气候条件下沉积了近千米厚的富有机质泥岩,同时在盆缘形成走滑构造转换带,为盆地东南部和北部分别提供了浅水/辫状河三角洲和扇三角洲前缘砂体的物源通道,其中,砂体与凹陷内的泥岩构成了优质的储-盖组合;(3)古近纪晚期的挤压-走滑构造作用控制了盆地内NE—SW向构造脊的发育,形成大量断背斜/断鼻圈闭并最终定型,该时期与油气充注Ⅱ期相匹配,控制了油气的富集与分布;(4)明确了Doseo盆地的油气成藏模式,其中,北部陡坡带以优质储层控藏为主,中部走滑构造带以断-盖配置控藏为特征,南部斜坡带以稳定盖层和保存条件控藏为关键。研究成果为Doseo盆地走滑构造带的油气勘探提供了重要依据。

关键词: 中非裂谷系, Doseo盆地, 多期走滑构造, 伸展-走滑, 挤压-走滑, 油气成藏