Geological investigation have led to discovery of huge tar sand deposits within Afowo Formation of the Turonian-Maastrichtianage (95.9-66.0 Ma) in the Nigerian sector of the Eastern Dahomey Basin. This study aims at determining the feasibility of exploiting the major hydrocarbon resource steam assisted gravity drainage enhanced recovery technique. Samples from three core holes were dry sievied to determine the particle size distribution and their sections studied using a petrographic microscope. Clay mineral content was determined using X-ray diffraction scanning electron microscopy. The granulometric analysis shows the bituminous sediments to be generally fine grained and moderate to well sorted, and the grains are angular to subangular. Porosity ranges from 15.5 to 33.6 ɸ with average value of 26.4 ɸ, while permeability ranges from 270 to 4800 mD, with an average value of 4800 mD (very high) recorded for the sandstones. Petrographic study, scanning electron microscopy and X-ray diffractometry showed quartz as the dominant mineral component, with subordinate feldspar and other accessory minerals. The predominance of quartz is probably due to its mechanical stability. The low frequency of feldspar is attributable to its susceptibility to chemical breakdown and alteration, respectively, during transport and after deposition, with latter accounting for the observed secondary porosity. Kaolinite is the common clay mineral present in the oil sands and may not have sufficiently reduced the reservoir quality to negatively impacting enhanced recovery operation by steam assisted gravity drainage.

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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.