西非被动大陆边缘盆地深水沉积体系特征

发布时间：2018-11-02 08:15

【摘要】：深水沉积砂岩储层是近年来全球油气勘探重点领域之一,对于深水沉积模式认识、沉积类型划分、储层分布规律及宏观演化规律能否实现系统深入的认知也成为制约全球油气勘探获得更多突破的关键问题之一。以典型深水沉积广泛发育的西非被动大陆边缘尼日尔三角洲盆地和刚果扇盆地为研究区,以地震资料为主,钻井资料为辅,开展针对性的深水沉积体系层序界面识别,明确研究区层序及体系域划分方案,建立深水沉积层序地层格架;综合2个研究区的深水沉积特征,探索建立了一套西非地区的深水沉积类型的划分方案,将其划分为陆坡峡谷、块体流、水道体、朵叶体、半深海泥5种亚相;将块体流细化为滑移体和滑塌碎屑流2种微相,将水道体进一步划分为高侵蚀充填型水道、低侵蚀过路加积型水道、过路高弯度水道、废弃水道、堤岸-漫溢5种微相,将朵叶体细分为末端朵叶和决口扇朵叶2种微相;同时系统总结解剖了各微相的岩性组合、地震反射及平面发育特征;深入分析了研究区深水沉积体系的宏观演化特征及展布规律,认识到尼日尔三角洲盆地深水沉积体系中水道体和朵叶体均有发育,自下向上,随着相对海平面先下降再上升的过程,早期主要发育朵叶体沉积,晚期则转变为以发育大型浊积水道为主。刚果扇盆地深水沉积则主要为水道体沉积,朵叶体较少发育,早期水道规模小,中期开始发育多支复合水道并呈退积趋势,水道发育程度逐渐降低,至晚期水道能量及侵蚀能力复又转强,甚至形成较大的陆坡峡谷及多支水道体。
[Abstract]:Deep-water sedimentary sandstone reservoir is one of the key fields of global oil and gas exploration in recent years. Whether the reservoir distribution law and the macroscopic evolution law can realize the systematic in-depth cognition also becomes one of the key problems which restricts the global oil and gas exploration to obtain more breakthrough. Based on the Niger Delta basin and Congo fan basin on the passive continental margin of West Africa, where the typical deep-water sediments are widely developed, the sequence interface identification of the deep-water sedimentary system is carried out, with seismic data as the main source and drilling data as the auxiliary. The research area sequence and the system tract division plan are defined, and the deep-water sedimentary sequence stratigraphic framework is established. Based on the characteristics of deep-water sediments in two study areas, a set of deep-water sedimentary types in West Africa was established, which was divided into five subfacies: slope canyon, block current, waterway body, flower leaf body and semi-deep sea mud. The block flow is divided into two kinds of microfacies: slip body and sloughing debris flow. The waterway body is further divided into five microfacies: high erosion filling channel, low erosion crossing road plus accumulation channel, crossing high bend channel, abandoned waterway, dike bank and overflowing 5 kinds of microfacies. The flower body was subdivided into two microfacies: the terminal leaf and the cleft leaf. At the same time, the lithologic assemblage, seismic reflection and plane development characteristics of each microfacies are systematically summarized and dissected. The macroscopical evolution and distribution of deep-water sedimentary system in the study area are analyzed in depth. It is recognized that both watercourse body and flower leaf body have developed in the deep-water sedimentary system of Niger Delta basin and are upward from the bottom down. With the process of relative sea level first falling and then rising, the early stage is dominated by the development of flower leaf bodies, and in the late stage, the development of large turbid hydrops is dominant. In the Congo fan basin, the deep-water sediments are mainly watercourse bodies, and the flower leaf bodies are less developed, the scale of the early waterways is small, and the multi-branch composite waterways are developed in the middle of the period, and the development degree of the watercourses decreases gradually. In the late stage, the energy and erosion capacity of waterways were strengthened, and even large slope canyons and multi-channel bodies were formed.
【作者单位】：中海油研究总院;
【基金】：国家“十二五”科技重大专项“非洲、中东重点勘探区油气地质评价及关键技术研究”(2011ZX05030-003) 国家“十三五”科技重大专项“西非和南美海域重点区油气地质评价及关键技术研究”(2017ZX05032-001)
【分类号】：P618.13

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