Carbon capture and sequestration technology has been a ground-breaking tool in tackling carbon dioxide (CO2) emissions worldwide but has limitedly been researched and practised in Africa at present. Considering the vast growth and developmental level in the continent, there is a need to consider this option of mitigating global climate change. In this study, a systematic and process-based incorporation of seismic and well logs datasets was used to characterize the structural and stratigraphic framework of sandstone reservoirs within the field in order to determine their capacities for effective CO2 sequestration. Petrophysical analysis, fault modelling as well as geostatistical techniques were used to build facies and property models which enabled a qualitative assessment of the sealing potential of faults associated with the reservoirs based on prediction of key properties such as shale gouge ratio, lithological juxtaposition, fault permeability and fault transmissibility across the fault faces. Nine water-bearing sandstone reservoirs (reservoirs A–J) with varying reservoir quality were identified in the field. The dominance of high SGR, low permeability, higher fault throws and low fault transmissibility values at the lower parts of the faults indicates the deeper structural traps of the field are low-risk zones and might serve as good storage areas for CO2.

The morphometry and spatial distribution of seabed pockmarks have been used as proxies for subsurface conditions and local hydrodynamics. We have characterized and analyzed the distribution of seabed pockmarks in the Freeman Field, offshore western Niger Delta using a high-resolution 3D seismic data to understand the relationships between pockmarks and their controlling factors. We identified a total of 684 pockmarks in the Freeman Field at water depths between 1461 and 2395 m. The pockmarks are circular, elliptical, and elongated in plan view, having U-, V-, and W-shaped geometries in cross-sectional view. The average length, width, and depth of the pockmarks are 210, 111, and 15 m, respectively. Some of the pockmarks were randomly distributed whereas the others were not. From statistical analysis, most of the pockmarks occurred within a water depth range of 1600–2100 m. The randomly distributed pockmarks occurred at variable water depths whereas the pockmarks that were aligned along fault planes occurred at shallow water depths (approximately 1400–1700 m). However, those confined within the canyon occurred at deeper water depths (approximately 1700–2400 m). Our results show no correlation between the water depth and any of the pockmark dimensions; therefore, we hypothesize that changes in water depth had no effect on any of the pockmark dimensions because the Freeman Field is located at water depths greater than 1000 m where the current velocity range is lower (0.2 and 0.42 m/s). Hence, pockmark dimensions were comparatively uniform throughout the study area. We suggest that the variation in pockmark morphometry is linked to seafloor currents and the activity history of the pockmarks whereas the spatial distribution is linked to structural and stratigraphic discontinuities. Furthermore, our results give insights to the factors that should be considered during risk assessment before hydrocarbon exploration and production.

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Three-dimensional (3D) seismic data and well logs from the Penobscot area, located within the Scotian Basin offshore Nova Scotia, are used to assess the role of mass-transport deposits (MTDs) on fault propagation. Four MTDs characterized by chaotic seismic facies were mapped, with the earliest hosted by the Late Cretaceous–Recent Dawson Canyon Formation and latest three hosted by the Banquereau Formation. Two types of faults were also mapped. R-faults are regional faults that cut across all the interpreted MTDs in the study area, while P-faults are polygonal faults that cut across MTDs 2 and 3 but tip out at the basal surfaces of MTDs 4 and 2. Representative seismic profiles and isochron maps of the MTDs and throw–depth (T–z) and throw–distance (T–x) plots allows us to distinguish the families and propagation history of the faults. Our results show that fault propagation is not affected by the presence or thickness variation of MTDs, and is also unaffected by lithological contrast in the Penobscot area of the Nova Scotian Shelf.

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