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Title: Deposition, remobilization and fluid flow in sedimentary basins : case studies in the northern North Sea and Nigeria Transform Margin
Author: Olobayo, Oluwatobi Anastasia
ISNI:       0000 0004 5360 0237
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2015
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Soft-sediment remobilization and fluid flow processes and their products such as sand injectites, mud volcanoes, pipes, pockmarks and authigenic carbonates constitute a key, but under-appreciated component of sedimentary basins. The structures are evidence of and provide focused fluid pathways bypassing the stratigraphic and structural framework and thus have numerous implications for hydrocarbon exploration and production by influencing sediment and fluid distributions. Recent advances in subsurface imaging using high-resolution 3D seismic data, integrated with well data, geochemical data and outcrop data have greatly improved the understanding of subsurface sediment remobilization and fluid flow processes in sedimentary basins. This study presents substantial new results from the description, analysis and interpretation of products of subsurface remobilization processes and fluid flow based on all available data from the Northern North Sea and the Nigeria Transform Margin. The studied intervals, which encompass the entire Cenozoic and Cretaceous succession, have undergone repeated, large-scale remobilization and deformation of sediments through time. The North Sea is the archetype Giant Injected Sand Province (GISP) with kilometre-scale sandstone intrusions observed within multiple stratigraphic intervals, but this is the first time the northern North Sea has been systematically studied on a regional scale. Seismic-scale sandstone intrusions are well documented along the Atlantic Margin from the South Viking Graben, Outer Moray Firth, Norwegian-Danish Basin, Faroe-Shetland Basin and Barent Sea but primarily emplaced during one or two episodes. Results from the NNS show evidence for five major episodes of emplacement. These sandstones, believed to be sourced from different stratigraphic levels, have intruded thick polygonally-faulted, diatomaceous and smectite-rich mudstones; probably facilitated by hydrocarbons and diagenetically-released water in spatio-temporally varying proportions. The Cenozoic section of the Nigeria Transform Margin comprises up to 2 km of sediments, including recurrent mass transport deposits ranging between a few to tens of kilometres in length and constituting up to 25 % of the stratigraphic section. A series of fluid flow features such as pockmarks, pipes, bottom simulating reflections, polygonal faults and mound have been interpreted on the seabed and in the overburden; all of which provide evidence of focused fluid movement in the subsurface becoming more abundant towards the Niger Delta. Our study provides details on the geometries, scale, spatial distribution, potential causative mechanisms and implications of these soft-sediment remobilized and fluid flow products; as well as their relationships with other depositional and structural elements within the basin. It also reveals the extent by which sedimentary basins can be affected by these processes and therefore be incorporated into present stratigraphic frameworks and improve reservoir models.
Supervisor: Huuse, Mads ; Taylor, Kevin Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Remobilization, Injection, Northern North Sea, Nigeria Transform Margin