Evolutionary characteristics and controlling factors of deep-sea fans in Cretaceous passive continental margin basin, Northern Subbasin, Senegal Basin

doi:10.13745/j.esf.sf.2020.12.12

Abstract

Abstract:

Deep-sea fan reservoirs in passive continental margin basins are among exploration hotspots in offshore petroleum exploration. Understanding the spatiotemporal evolution of deep-sea fans can help refining geological models by enhancing the exploration and development of related reservoirs. Based on seismic and drilling data, different types of deep-sea fans with characteristic lithologies, shapes, and sizes are identified along the passive continental margin of the Senegal Basin. Factors such as sea-level changes, sediment supply, and paleo-geomorphology were integrated into the interpretation. This study shows that the passive continental margin dates back to the Middle Jurassic. During the Cretaceous Age, the study area underwent three stages of tectonic-sedimentary evolution: (1) carbonate platform build-up stage during the Neocomian and Aptian Ages; (2) sedimentary stage of clastic deposition on a continental fault-slope from the Albian to Santonian Ages; and (3) sedimentary stage of clastic deposition on a gentle continental slope (slope-break) during the Campanian and Maastrichtian Ages. During these periods, five types of deep-sea fans with varied lithologies, morphologies, and sizes developed in the study area. Several factors could have influenced the development and evolution of deep-sea fans. Among them, global sea-level changes and terrestrial clastic supply had the greatest influence on the texture and size of the fan, while continental slope geomorphology determined the shape and distribution of the fan reserviors.

Key words: Senegal Basin, Cretaceous, passive continental margin, deep-sea fan, evolutionary characteristics, controlling factors

CLC Number:

WANG Hongyu, ZHANG Feng, YANG Xiongbing. Evolutionary characteristics and controlling factors of deep-sea fans in Cretaceous passive continental margin basin, Northern Subbasin, Senegal Basin[J]. Earth Science Frontiers, 2021, 28(2): 362-375.

Figures/Tables 10

Fig.1 Location and geologic setting of the study area. Modified after [12,13,14].

Fig.2 Tectonostratigraphic chart of the Senegel Basin, with indication of temporal distribution of deep-sea fans in the Cretaceous (stratigraphic data form references [12]; sea level data from [25,26])

Fig.3 A schematic tectonic evolutionary model (profile location see ‘AB line’ in Fig.1)

Fig.4 Seismic profile (‘CD line’ in Fig. 1) with geological interpretation

Fig.5 Characteristics and geologic interpretation of seismic attributes (root mean square amplitude) for the 3D seismic survey area

Fig.6 Sketch maps showing the tetono-sedimentary evolution of the study area during the Cretaceous Period

Fig.7 A developmental model for the Cretaceous deep-sea fan system in the study area

Table 1 Developmental environments, identification characteristics, and reservoir quality assessments of the Cretaceous deep-sea fan system in the study area

时间/地层	陆架区沉积环境	陆坡类型与特征	深海扇体特征				储层性能勘探潜力
时间/地层	陆架区沉积环境	陆坡类型与特征	岩性组合	测井响应(GR)	地震相	规模	储层性能勘探潜力
Neocomian-Aptian	碳酸盐岩台地	台地边缘斜坡	灰质粉砂岩、碳酸盐岩碎屑	泥岩基线夹针状突起	中强振幅平面呈枫叶状	单层薄面积小	较差
Albian	三角洲体系	断层斜坡下切沟谷	砂岩、粉砂岩与泥岩互层	钟型、指状	中强振幅平面扇形裙带剖面楔形	单层厚面积较大	好
Cenomanian-Turonian	浅海相,偶尔碳酸盐岩沉积	断层斜坡下切沟谷	泥质粉砂岩与灰质泥岩	泥岩基线夹针状突起	中等连续多期切割叠置平面呈扇形	累计厚度大面积较大	中等
Coniacian-Santonian	浅海相	断层斜坡下切谷规模大	泥质粉砂岩与粉砂质泥岩	泥岩基线夹低幅度针状	中等振幅平面呈鸟足状	单层薄延伸距离长	中等-较差
Campanian-Maastrichtian	三角洲体系- 浅海相	沉积坡折带	粉砂岩与泥质粉砂岩	泥岩基线夹针状、指状	中等振幅层薄,平面呈扇形、指状	单层较蒲面积大	中等-较好

Fig.8 Evolutionary characteristics of continental slope topography in the study area

Fig.9 Model diagrams showing the coevolution of the continental slope geomorphology and deep sea fan features in the study area

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时间/地层	陆架区沉积环境	陆坡类型与特征	深海扇体特征				储层性能勘探潜力
时间/地层	陆架区沉积环境	陆坡类型与特征	岩性组合	测井响应(GR)	地震相	规模	储层性能勘探潜力
Neocomian-Aptian	碳酸盐岩台地	台地边缘斜坡	灰质粉砂岩、碳酸盐岩碎屑	泥岩基线夹针状突起	中强振幅平面呈枫叶状	单层薄面积小	较差
Albian	三角洲体系	断层斜坡下切沟谷	砂岩、粉砂岩与泥岩互层	钟型、指状	中强振幅平面扇形裙带剖面楔形	单层厚面积较大	好
Cenomanian-Turonian	浅海相,偶尔碳酸盐岩沉积	断层斜坡下切沟谷	泥质粉砂岩与灰质泥岩	泥岩基线夹针状突起	中等连续多期切割叠置平面呈扇形	累计厚度大面积较大	中等
Coniacian-Santonian	浅海相	断层斜坡下切谷规模大	泥质粉砂岩与粉砂质泥岩	泥岩基线夹低幅度针状	中等振幅平面呈鸟足状	单层薄延伸距离长	中等-较差
Campanian-Maastrichtian	三角洲体系- 浅海相	沉积坡折带	粉砂岩与泥质粉砂岩	泥岩基线夹针状、指状	中等振幅层薄,平面呈扇形、指状	单层较蒲面积大	中等-较好

时间/地层	陆架区沉积环境	陆坡类型与特征	深海扇体特征				储层性能勘探潜力
时间/地层	陆架区沉积环境	陆坡类型与特征	岩性组合	测井响应(GR)	地震相	规模	储层性能勘探潜力
Neocomian-Aptian	碳酸盐岩台地	台地边缘斜坡	灰质粉砂岩、碳酸盐岩碎屑	泥岩基线夹针状突起	中强振幅平面呈枫叶状	单层薄面积小	较差
Albian	三角洲体系	断层斜坡下切沟谷	砂岩、粉砂岩与泥岩互层	钟型、指状	中强振幅平面扇形裙带剖面楔形	单层厚面积较大	好
Cenomanian-Turonian	浅海相,偶尔碳酸盐岩沉积	断层斜坡下切沟谷	泥质粉砂岩与灰质泥岩	泥岩基线夹针状突起	中等连续多期切割叠置平面呈扇形	累计厚度大面积较大	中等
Coniacian-Santonian	浅海相	断层斜坡下切谷规模大	泥质粉砂岩与粉砂质泥岩	泥岩基线夹低幅度针状	中等振幅平面呈鸟足状	单层薄延伸距离长	中等-较差
Campanian-Maastrichtian	三角洲体系- 浅海相	沉积坡折带	粉砂岩与泥质粉砂岩	泥岩基线夹针状、指状	中等振幅层薄,平面呈扇形、指状	单层较蒲面积大	中等-较好