Clay impact on reservoir quality in the Nubia Formation of Saqqara field, Gulf of Suez, Egypt

This study aims to investigate the impact of clays on the quality of the Nubia reservoir in the Saqqara field, Gulf of Suez, Egypt. The research will contribute to a broader knowledge of reservoir characterization, offering valuable insights for similar geological settings in other regions, thereby aiding in the optimization of resource management in global petroleum industries. The shale evaluation procedure involves three primary steps: estimating shale volume, identifying clay minerals, and assessing shale distribution. The neutron-density (N-D) method was employed to estimate the shale volume in the Nubia reservoir, yielding an average of 0.6% across four wells, with a maximum recorded value of 2.2% in well GS323-3. These values represent that the Nubia reservoir contains a negligible amount of shale, indicating that the porosity and permeability are high. Clay mineral analysis, based on a Potassium-Thorium (K-Th) and Potassium-PEF cross-plots, identified the presence of chlorite, illite, montmorillonite, and heavy thorium-bearing minerals, where chlorite and illite enhance the mechanical stability of the reservoir, while montmorillonite may cause issues with swelling and pressure. Thorium-bearing heavy minerals are typically associated with reduced permeability due to their influence on chemical interactions. The shale distribution analysis, conducted using the Thomas and Stieber model, confirms the overall cleanliness of the Nubia reservoir. Most formation data points align with the 0% shale line, indicating high total porosity, while only a few points fall along the dispersed shale line. In conclusion, the findings indicate that the Nubia reservoir exhibits minimal shale content, predominantly clean lithology, and favorable porosity and permeability characteristics. Consequently, the reservoir is classified as high-quality, making it suitable for efficient hydrocarbon production.