Integrated Seismic and Sedimentological Workflow to De-Risk Deep Oligocene Exploration in the Nile Delta: Implications for Overpressured Plays in the Mena Region

Abstract

Deep Oligocene prospects in the offshore Nile Delta represent a material gas exploration opportunity, yet they are associated with elevated subsurface uncertainty related to overpressure development, trap integrity, and pronounced lateral reservoir heterogeneity. Several exploration failures in the basin highlight the need for integrated workflows that jointly address geological risk, drilling safety, and trap effectiveness. This study presents a fully integrated seismic-sedimentological-petrophysical workflow applied to the Baltim Field area, designed to de-risk deep Oligocene exploration through improved reservoir prediction, pore-pressure assessment, and seal integrity evaluation. The Oligocene succession was subdivided into six reservoir units using calibrated well logs, core data, and seismic facies analysis. Robust seismic-to-well ties were established through synthetic seismograms, enabling detailed structural interpretation and multi-attribute seismic analysis. Time, velocity, and depth maps were generated for each reservoir horizon, while seismic attributes (amplitude, phase, and frequency) were used to refine stratigraphic architecture and identify sand-prone fairways. Petrophysical evaluation, supported by litho-saturation cross-plots and iso-parametric maps, constrained lateral variations in porosity, water saturation, and reservoir thickness. A key component of the workflow is the construction of a 3D pore-pressure and fracture-pressure model integrating seismic velocities, calibrated well data, and established rock-physics relationships. The model delineates overpressure distribution, evaluates seal integrity, and identifies pressure-controlled compartments. Results demonstrate that preserved overpressure plays a critical role in both trap integrity and exploration risk, explaining historical exploration failures and validating intact traps in undrilled closures. The integrated analysis reveals that reservoir quality is strongly controlled by depositional elements including confined channels, lobe complexes, and distal turbidites, while pressure regime and fault behavior govern hydrocarbon retention. The workflow provides a predictive framework for prospect ranking, safer drilling design, and optimized well placement. Its applicability extends beyond the Nile Delta, offering transferable insights for overpressured deep-water plays across the MENA region.