塞内加尔盆地北部次盆白垩系被动大陆边缘深海扇演化特征及主控因素

doi:10.13745/j.esf.sf.2020.12.12

摘要/Abstract

摘要：

被动大陆边缘深海扇是当今海洋深水油气勘探的热点。识别深海扇,明确其时空演变特征,总结关键地质因素对其发育的控制作用,对于建立深海扇成因与预测地质模型具有重要意义。本文通过地震与钻井资料综合解释,分析塞内加尔盆地北部次盆白垩纪被动大陆边缘时期的构造-沉积演化特征,识别深海扇体,并分析其岩性、形态与规模的演变特征;然后分析海平面变化、陆源物质供给、陆坡与沟谷地貌等地质条件对深海扇体发育的控制作用。研究表明,研究区在白垩纪盆地被动大陆边缘阶段,经历了早白垩世的碳酸盐岩台地建设期、Albian-Santonian期碎屑岩沉积被陆坡内外分割的沉积期、Campanian-Maastrichtian期的碎屑岩缓坡沉积期等3个构造-沉积演化阶段;从早白垩世Aptian期到白垩纪末期发育了具有不同岩性、形态与规模特征的深海扇体。全球海平面变化、陆源碎屑供给、陆坡与沟谷地貌特征共同制约了深海扇的演化特征,但它们对深海扇发育与演化的影响作用又有所不同。全球海平面变化与陆源碎屑供给特征更多是影响了扇体的岩性粗细与规模,而陆坡沟谷地貌特征则直接决定了扇体的形态与分布。

关键词: 塞内加尔盆地, 白垩系, 被动大陆边缘, 深海扇, 演化特征, 控制因素

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

中图分类号:

王宏语, 张峰, 杨雄兵. 塞内加尔盆地北部次盆白垩系被动大陆边缘深海扇演化特征及主控因素[J]. 地学前缘, 2021, 28(2): 362-375.

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.

图/表 10

图1 研究区位置与地质概况图(盆地平面图修自参考文献[12],剖面图修自参考文献[13,14])

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

图2 盆地构造-地层序列特征与白垩系深海扇类型(地层资料修自参考文献[12],海平面变化曲线来自文献[25,26])

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])

图3 构造演化剖面(图1的A-B位置)

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

图4 三维地震解释剖面(图1的C-D位置)

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

图5 三维地震工区均方根地震属性特征及其地质解释 A—Aptian阶顶部250 m厚度;B—Albian阶底部200 m厚度;C—Coniacian阶底部180 m厚度;D—Campanian-Maastrichtian阶总厚度的下部1/2厚度。

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

图6 研究区白垩纪构造-沉积平面格局 A—晚侏罗-早白垩世Neocomian期;B—Aptian期;C—Albian期;D—Cenomanian-Turonian期。

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

图7 研究区白垩系深海扇发育模式图

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

表1 研究区白垩系深海扇体发育环境、识别特征及储层性能评估

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

图8 研究区陆坡地貌演化特征

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

图9 研究区陆坡地貌与深海扇体特征的对应演变关系模式图

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