西非下刚果盆地深水水道发育特征及沉积储层预测

The development characteristics of deep water channel and sedimentary reservoir prediction in Lower Congo basin,West Africa

为了较为全面地描述西非下刚果盆地中新统水道的特征、成因、分布规律和砂体展布,将深水水道的描述参数归纳为几何参数、侵蚀能力、限制条件、发育期次、外部形态、内部结构和砂体情况等7类,将西非下刚果盆地深水水道分为轴部切谷充填水道、侵蚀型复合水道、侵蚀型单支水道、加积型堤岸水道和加积型朵叶化水道等5类。轴部切谷充填水道侵蚀能力最强,规模最大,含砂率高,是在切谷强限制条件下形成的多支多期复合水道群;侵蚀型复合水道发育最多、规模较大、侵蚀能力较强,含砂率较高、砂体分布较广,属限制条件下形成的水道复合体,是研究区的主要勘探目标;侵蚀型单支水道侵蚀能力相对变弱,属弱限制条件下形成的期次较少的水道,规模较小;加积型堤岸水道侵蚀能力较弱,加积作用较强,属弱限制条件下相对顺直的水道,规模较小;加积型朵叶化水道侵蚀能力最弱,是在非限制条件下形成的水道,其席状朵叶砂体含砂率较高、分布较广,是研究区的次要勘探目标。这5类水道分别发育于下刚果深水扇的不同部位,经历了不同的沉积演化阶段。在深水水道发育特征研究的基础上,对研究区东北部A区块SQ1—SQ7沉积相及储层进行了预测,并指出海平面变化和构造抬升是控制下刚果盆地深水沉积类型及分布的主控因素,钻前预测结果和钻探结果吻合度较高,证明了本文预测技术和研究思路的正确性和可行性。

In order to describe the characteristics, origin, distribution, and sand body distribution of deep water channel in Miocene in Lower Congo basin, West Africa, the deep water channel description parameters are divided into 7 classes, respectively is. geometrical parameters, erosion ability, confined conditions, development period, external morphology, internal structure and sand body condition. The deep water channels in Lower Congo basin can be divided into 5 types, respectively is. axial valley-fill channel, erosional complex channel, erosional single channel, aggradational leveed channel and aggradational lobed channel. Among them, the axial valley-fill channel erosion ability is strongest, scale is largest, and sand content is highest. It is a multi-branch and multi-period channel group formed under strongest confined conditions. The erosion complex channel is widely developed, scale is larger, erosion ability is stronger, sand content is higher, sand body is widely dis- tributed. It is a complex channel formed under strong confined conditions, which is the main exploration target in the study area. The erosion ability of erosional single channel is relatively weak, and it is less-period and smaller channel formed under weaker confined conditions. Aggradational leveed channel has the weaker erosion ability and stronger aggrading action. It is a relatively straight channel formed under weaker confined condi- tions. Aggradational lobed channel has the weakest erosion ability, and it is formed under non-confined condi- tions. The sheet lobe sand is higher sand content ratio and widest distribution, and it is the second exploration target in the study area. These 5 types of channels are developed in different parts of Congo deep water fan, and have experienced different stages of sedimentary evolution. On the basis of the research of deep water channel development characteristics, the sedimentary facies and reservoir are predicted in northeast of the study area （A block）. It is pointed out that the sea level change and tectonic uplift are the main controlling factors for the types and distribution of deep water sedimentary in Lower Congo basin. Pre-drilling prediction results and drilling results are coincident, which proves the correctness and feasibility of this prediction techniques and research ideas.