西非深水沉积类型特征及油气勘探意义

深水沉积储层是目前世界油气勘探开发的热点目标，西非深水油气资源丰富，占全球深水油气总资源量的14%。根据深水沉积所处位置、沉积相带、沉积物组合及平面展布特征等差异，将深水沉积类型分为水道（单支水道、复合水道）、朵叶（单期朵叶、叠合朵叶）、天然堤（近端天然堤、远端天然堤）和深海泥。通过对不同类型深水沉积的岩相、测井相、地震相和沉积相进行分析，以深水沉积模式为指导，结合物源供给和运输通道等因素的影响，阐明了西非尼日尔三角洲盆地和下刚果-刚果扇盆地油气勘探的主要储层类型及分布。综合研究表明，复合水道浊积砂和叠合朵叶席状砂是深水沉积的主要储层，储层物性良好；近端天然堤席状砂是较好的储集体；单支水道和远端天然堤受到砂体规模和厚度的限制，储层性能一般。在尼日尔三角洲盆地深水区勘探中，首选低缓构造背景下的叠合朵叶席状砂体，其次是寻找高陡构造背景下的叠合朵叶席状砂体，最后是寻找低缓构造背景下的复合水道浊积砂体。在下刚果-刚果扇盆地深水勘探中，以寻找复合水道浊积砂体为主，其次为叠合朵叶席状砂体。

Type features and hydrocarbon exploration significance of deepwater sedimentary in West Africa

Nowadays deepwater sedimentary reservoirs are hotspots of hydrocarbon exploration and exploitation in the world, the West Africa abounds in deepwater hydrocarbon resource, which accounts for 14% of total deepwater hydrocarbon resource worldwide. Based on the differences in deepwater sedimentary location, sedimentary facies belt, sediment association, and 2D distribution characteristics, deepwater sedimentary are divided into four types, i.e., channels (single and complex channels), lobes (single and superposed lobes), levees (proximal and distal levees), and deepsea mud. Directed by a deepwater sedimentary model in consideration of such factors as provenance supply and transport pathway, the lithofacies, logging facies, seismic facies and sedimentary facies of different types of deepwater sedimentary was studied, thus determining the types and distribution of main reservoirs for hydrocarbon exploration in the Niger Delta Basin and the Lower Congo-Congo Fan Basin, West Africa. Overall research indicates that turbidite sand in complex channels and sheet sand in superposed lobes are the main reservoirs developed from deepwater sedimentary with good physical properties; sheet sand in proximal levees is relatively good reservoir body; single channels and distal levees have moderate reservoir properties due to limitation in sand body size and thickness. The following sand bodies are orderly explored in deepwater areas in the Niger Delta Basin, i.e., sheet sand bodies in superposed lobes under low and gentle tectonic setting, sheet sand bodies in superposed lobes in high and steep tectonic setting, and turbidite sand bodies in complex channels under low and gentle tectonic setting. Moreover, deepwater exploration in the Lower Congo-Congo Fan Basin is aimed at detecting turbidite sand bodies in complex channels and sheet sand bodies in superposed lobes.