Hydrocarbon potential and reservoir characteristics of incised-valley transgressive sandstones: A case study of the Messinian gas reservoirs (Nile Delta Basin, Egypt)

Abstract

The incised-valley sandstones have been identified as a significant contributor to global hydrocarbon resources. This study aims to assess the Messinian Abu Madi (AM) sandstone's reservoir properties in the incised valleys of the Baltim, Nidoco, and Abu Madi gas fields in the Nile Delta Basin, Egypt. The hydrocarbon potential of these sandstones is assessed through the analysis of seismic, well logs, and core data. The seismic interpretation reveals that extensional faults played a significant role in controlling the deposition of the Abu Madi Formation in the study area, formed during the tectonic rifting of the Messinian age. The northernmost portion of the study area in the Abu Madi field exhibits the most promising location for gas exploitation, suggesting the need for further exploration and evaluation. The sandstones exhibit a fining upward trend with a relatively clean composition, moderate to well sorting and mild calcareous tendencies. The presence of sedimentary structures, such as cross-bedding and ripples, suggests a dynamic depositional environment. The rock composition, dominated by quartz with variable sorting and cementation, influences the porosity and permeability of the sandstones. Petrophysical investigations indicate favourable reservoir conditions with significant porosity and permeability, enhancing hydrocarbon storage and extraction potential. The analysis of petrophysical parameters in the AM sandstones reveals favourable properties for gas production, including low shale content (4%–12%), high porosity (18%–22%), and low water saturation (20%–54%) levels. The findings of this study indicate that the gas-pay zones within the Abu Madi sandstones are primarily associated with the transgressive sandstones of the estuarine facies (TST) rather than the lower sandstones of the fluvial facies (LST). The complex sandstone channels within the TST exhibit diverse geometries and contribute to reservoir heterogeneity. The presence of well-connected channels enhances reservoir productivity by facilitating fluid flow. The understanding of the distribution and characteristics of these channels is essential for reservoir characterisation and optimisation of hydrocarbon recovery.