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The upper Cretaceous clastic facies of the Bahariya Formation host the main reservoir intervals in the north Western Desert (NWD) of Egypt. These clastics were deposited in a parallic depositional environment characterized by different scales of reservoir heterogeneities. However, the link between these heterogeneities and the depositional setting of the reservoir facies is still blurred. In this study, we investigate a highly-heterogeneous reservoir facies of Bahariya Formation in Yasser Field wells, NWD in order to construct a predictive framework for the distribution of the best reservoir rock types (RRTs) and flow zones. Seismic stratigraphy was integrated with core sedimentology to understand the depositional architecture of the reservoir facies. Moreover, conventional core analysis and wireline logs were interpreted to evaluate the scales of lithological and petrophysical heterogeneities in the different RRTs. In the studied Yasser Field, the Bahariya Formation consists of tidal facies deposited in a wide range of tidally-influenced conditions. The seismic facies varies greatly with variation in the tidal regime. Best reservoir rock types RRTs are associated with tidal channels and amalgamated tidal bars (RRTI). RRTI rocks represent the main fluid flow conduits in the studied Bahariya reservoir. Lithological and petrophysical heterogeneities are more prominent in the tidal mud flat and mixed tidal flat facies which form RRTIII rocks. Linking seismic with sedimentary facies enabled us to predict the distribution of the best reservoir flow zones in the study region. The present results establish a framework for predicting the optimum reservoir quality facies based on integrating seismic, sedimentary and petrofacies. This framework could be applied in analogous tidally-influenced reservoir facies with high depositionally-controlled pore system heterogeneity. • Seismic and sedimentary facies of Bahariya Formation have been studied. • Bahariya sediments were deposited in tidal environment. • Large-scale reservoir heterogeneity has been reported. • Tidal channels and tidal bars have the best reservoir quality. [ABSTRACT FROM AUTHOR]

The Devonian sedimentary succession hosts the most potential reservoir targets in Ghadames Basin, Northwest Libya. This succession consists of a complex pattern of siliciclastic facies deposited during successive episodes of sea level fall and rise, thereby leading to a large scale heterogeneity in sandstone facies connectivity and distribution. The present study integrates core sedimentology, wireline logs, and routine and special core analysis to establish a framework for predicting the distribution of the best Devonian reservoir rock types (RRTs). A lowstand amalgamated fluvial sandstone bars only exist in the Lower Devonian Tadrart Formation; the other Devonian rock units consist of transgressive and highstand tidally-influenced estuarine and deltaic facies. The pore system characteristics are controlled by initial depositional attributes where open, megapores with entry displacement pressures <10 psi occur in the quartzose, high energy fluvial sandstone bars, delta distributary channels and mouth bars. These facies are classified as RRTI and are mostly associated with lowstand and late highstand facies. In contrast, the other RRTs display tight pore system with elevated irreducible water content >20%. RRTI rocks account for greater than 90% of the fluid flow capacity in the Devonian reservoirs. A link between the facies depositional setting, RRT distribution, vertical amalgamation and lateral compartmentalization of flow conduits, barriers and baffles zones has been proposed, thereby promoting the predictability of the best reservoir targets. • The depositional evolution of the Devonian rock units in south central Ghadames Basin, Libya has been revisited. • The petrophysical properties of the Devonian rock units were also investigated. • The distribution of the Devonian reservoir rock types (RRTs) has been linked to their depositional evolution. • The best RRTs are often associated with the lowstand facies in the Lower Devonian succession. [ABSTRACT FROM AUTHOR]

The eastern part of the offshore Nile Delta is one of Egypt's most productive gas provinces. This study utilizes well logs dataset and 2D seismic from Port Fouad marine (PFM) Field to investigate reservoir lithofacies, rock-types as well as the associated gas chimneys, pockmarks, bright anomalies of escaping fluids in the seafloor, and high-faulted zones caused by the chimney's developments. First, structural smoothing and median filters are used to improve the continuity of the stratigraphic horizons while preserving various geological structures, in order to pick all formation tops and structural faults. Afterwards, variance and energy attributes were computed and extracted for amplitude enhancement of various geobodies such as faults, gas chimneys, and bright reflectors. After that, petrophysical analyses revealed that the Upper Miocene Wakar Formation hosts scattered, thin gas pay zones (<10m) with low hydrocarbon saturation values (average S hc = 27.9%), high water saturation (average S w > 70%), and high shale volume (average V sh > 30%). These poor reservoir characteristics prevented accumulation of thick gas zones, thereby several gas escape features (e. vertical chimneys) are observed in the region. Finally, the estimated petrophysical parameter logs and the structure maps derived from seismic data are crucial components of the built 3D structural model. This model reveals the presence of four major normal faults (F1, F2, F3, and F4) oriented NW-SE and WNW-ESE, creating grabens and half grabens. These major faults (F1, F2, F3, and F4) are directly related to the inverted tectonics during the Cretaceous-Paleogene compression (Syrian Arc phase). A link between these structural patterns and gas escape zones is proposed, and the absence of good reservoir facies likely promoted an active phase of gas seepage in the study region. In addition, such gas escape chimneys can create catastrophic events on the seafloor and are considered direct evidence for the presence of gas generation and failure in accumulation. • Several subsurface gas seepage zones were reported offshore Nile Delta. • Subsurface imaging and seismic attributes configure the gas seepage regions. • Highly-faulted zones dissecting gas reservoirs are potential gas conduits. • Poor reservoir characteristics prevented gas accumulation at depth. • Gas escape provide direct evidence for gas generation and failure in accumulation. [ABSTRACT FROM AUTHOR]

The Early Cretaceous late syn-rift sediments of Alam El Bueib Formation host potential, however poorly-explored reservoir targets in the north Western Desert of Egypt. The controls on depositional evolution and architecture of Alam El Bueib sedimentary facies, as well as the influence of depositional attributes on reservoir facies heterogeneity, are poorly constrained. Therefore, this study integrates seismic, sedimentological, and petrophysical data from Meleiha concession in the north Western Desert to build evolutionary models for Alam El Bueib succession and predict the architecture of the potential reservoir facies. Several channel systems were observed with a notable upward transition from complex-filled to flat-filled channels. The complex-filled channels correspond to the early highstand tidally-influenced estuarine, deltaic/estuarine sediments of Alam El Bueib-IV and Alam El Bueib-IIIG units. Matruh canyon and Alam El Bueib-IIIG fluvial sand bars were developed during a phase of forced regression, and the canyon was infilled by hemiplegic mudstones during the Late Valanginian sea level rise. The late highstand and lowstand facies of Alam El Bueib-IIIG unit present the main fluid flow conduits. The minimal degree of reservoir heterogeneity occurs in the lowstand amalgamated fluvial sandstone bars, whereas lateral and vertical reservoir heterogeneity increases in the deltaic/estuarine and estuarine successions of Alam El Bueib-IIIG and Alam El Bueib-IV, respectively. The lateral compartmentalization of the Alam El Bueib-IIIG fluvial facies against Alam El Bueib Matruh canyon shales produced excellent stratigraphic traps that should be tracked throughout the entire north Western Desert. • Seismic and sedimentary facies of AEB Formation have been studied. • Several channel-fill seismic facies were recognized. • The channel geometry and infill characteristics vary with sequence stratigraphic framework. • Amalgamated fluvial sand bars of AEB-IIIG unit contain the main fluid-flow conduits. • The shale-infill of the regressive Matruh Canyon played an important role in hydrocarbon entrapment. [ABSTRACT FROM AUTHOR]

North Western Desert (NWD) of Egypt is one of the most petroliferous provinces in North Africa. Mesozoic rift basins in the NWD host several active petroleum systems in their syn- and post-rift sedimentary successions. Also, numerous oil reserves were recently discovered in the pre-rift Paleozoic reservoirs. However, the genetic link between the pre-rift hydrocarbon plays and the syn- and post-rift accumulations is still ambiguous. Additionally, controls on distribution of the optimum rock types in the pre-rift reservoirs need further investigation. Therefore, this study integrates geochemical, seismic-stratigraphic, and petrophysical approaches to better understand these issues based on oil, seismic, and well data retrieved from the Paleozoic pre-rift "Shiffah" and the Cretaceous late syn-rift "Alam El Bueib (AEB)" sandstones in PTAH oil Field in the NWD. Oil retrieved from Shiffah and AEB pay zones displays a similar n-alkane composition dominated by cycloalkanes and nC 20+ alkanes. The oil samples retain biomarker signatures of pre-Cretaceous terrestrial organofacies where oleanane is absent, isoprenoid ratio (prestane/phystane) is high (>5) and C 29 /C 27 steranes is greater than 1.5. Shiffah and AEB oils have a common source rock and display compositional characteristics similar to NWD oils derived from the Middle Jurassic Khatatba Formation fluvio-deltaic organofacies. Deep-seated rift-faults cross-cutting the entire syn- and pre-rift successions provide the paths for the upward and downward hydrocarbon migration from Khatatba organofacies to AEB and Shiffah sandstones, respectively. Distribution of the reservoir rock types (RRTs) controlled the thickness of the hydrocarbon column. Reservoir quality decreases from RRTI to RRTIII. RRTI rocks occur in the Shiffah fluvial basin-fill facies, whereas the best RRTs in AEB are classified as RRTII and are exclusively associated with the prograding deltaic facies. Correlation between seismic facies and RRT allows the prediction of their lateral and vertical distribution. Our results highlight existence of excellent reservoir rock types in the pre-rift succession connected with the Jurassic kitchen which charged the entire syn- and post-rift reservoirs. • Detailed rock typing for pre-rift reservoirs in the Western Desert was performed. • Hydrocarbon-source correlation reveals a similar petroleum system for pre- and late syn-rift oils. • Middle Jurassic syn-rift organofacies are the main source of hydrocarbons. • Pre-rift clastics have better reservoir rock types. • Rift-faults are the main migration paths for oils within both pre- and late syn-rift reservoirs. [ABSTRACT FROM AUTHOR]