Abstract
The decline in reservoir pressure and rate of production have prompted a series of studies to better characterize and define reservoir architecture in anticipation of ultimate recovery of the hydrocarbon deposits by a fluid-injection program in the Tovo field located in the coastal swamp depobelt of the Niger Delta Basin. This study utilizes the integration of well logs, biostratigraphic and 3D seismic data sets to establish a third-order sequence stratigraphic framework consisting of fourth-order sequences. It facilitates the construction of predictive depositional models that elucidate reservoir facies distribution, and architecture. Three types of reservoir deposits that are generally composed of channel and shoreface sandstone facies have been considered: lowstand fluvial sediments with a bulging geometry, marine-influenced sandstone deposits defined by strike-oriented tabular geometry, and highstand fluvial channel sandstone deposit characterized by dip-oriented lobate geometry. Intrareservoir shale, discontinuous shale stringers and/or shale lensoids, which are products of channel avulsion, overbank sedimentation, and marine flooding define the internal reservoir architecture. Their overall reservoir quality is very good. However, the fluvial-dominated sandstone deposits show a wide range of porosity and permeability across individual wells. Conversely, the marine-influenced reservoir deposits show better lateral and vertical sand connectivity as suggestive of near similar in the range of porosity and permeability values across the field, implying a better oil sweep efficiency and fluid-injection potential. The results of this study suggest that the depositional environment of sandstone reservoirs of the basin is complex but not infinite in facies distribution. The spatial distribution of these sandstone reservoir facies is related to changes in local accommodation space in the basin. This study, therefore, demonstrates the importance of evaluating the impact of sequence stratigraphic controls on reservoir characterization and architecture of hydrocarbon-bearing sandstones for optimum exploration and production in clastic depositional settings.
Published Version
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