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Integrating Sedimentology and Quantitative Rock Physics for Reservoir Characterization and Modeling in Field Development: A Case Study of an Onshore Field in Niger Delta, Nigeria


Most of the fields in the onshore Niger Delta are undeveloped several years after discovery. Among the numerous challenges that have hindered optimal development of these fields include geological uncertainties such as complex reservoir geometry, spatial and temporal variation of reservoir fluid. Hence, this study is aimed at improving the geological understanding of the reservoir systems by integrating sedimentology and quantitative rock physics for optimal field development. The objectives of this study include: to reconstruct the depositional environment of the reservoir sands, investigate the presence of stratigraphic barriers to lateral fluid variation, construct predictive reservoir model for simulation, and finally define optimal field development strategy. Analogs, core, logs, seismic, and production data were integrated in the study. The methodology and workflow for the study have combined simultaneous amplitude variation with offset (AVO) inversion, seismic geomorphology, static modeling, and dynamic simulation. Segmentation of the AVO inversion attributes including: shear impedance, lambda-rho and mu-rho into discrete facies classes revealed macro-scale sedimentary features such as barrier mouth bar and braided channel systems with cross-cutting relationship on horizon slices. Evidence from core interpretation supports a bay/lagoon marginal marine environment with characteristic layer cake and labyrinthine sand geometry. The conceptualization of the sedimentary environment and the sand geometry defined from the inversion attribute characterization, formed input for constructing a predictive reservoir model. The dynamic simulation of forty years production from the reservoir model gave a match of less than 10% difference between the simulated and historical production of oil and water respectively. Consequently, a 3 horizontal wells case with 4-1/2 inch tubing size and 1500 inch drain length, have been selected as the most realistic option for optimal field development and oil production at 1500 barrel per day rate using gas lift recovery mechanism. Finally, the integration of simultaneous AVO inversion, attribute segmentation, and sedimentology has reduced the geological uncertainty that had hindered optimal development in the field. This integrated methodology and workflow will serve as analog in solving complex geological problems and the associated development challenges in similar reservoir systems.