Influence of Shale on Petrophysical Properties and Reservoir Quality: Insights from the Matulla Formation, Saqqara Field, Gulf of Suez, Egypt

Abstract

This study examines the impact of shale volume (Vsh) and clay mineral distribution on the petrophysical properties and reservoir quality of the Matulla Formation in the Gulf of Suez, a critical factor in global hydrocarbon exploration and production. Understanding how shale affects porosity, permeability, and fluid saturation enhances reservoir characterization, optimizing recovery techniques such as hydraulic fracturing and sustainable resource management. The evaluation process involved calculating shale volume using the neutron-density method, with values ranging from 1.9% to 11% across four wells (GS323-1, GS323-2A, GS323-3, GS323-4A). Clay minerals have been identified through Potassium-Thorium (K-Th) cross-plot include chlorite, illite, kaolinite, montmorillonite, and mixed-layer clays. Montmorillonite and chlorite negatively impact porosity and permeability, while kaolinite and illite improve hydrocarbon retention. Shale distribution analysis using the Thomas and Stieber model showed both laminated and dispersed forms, where laminated shales had minimal blockage, and dispersed clays significantly reduced the reservoir quality. Results reveal that wells with low Vsh (GS323-1 and GS323-4A) which ranges from 1.5 to 2% exhibit excellent reservoir quality, with high porosity (14%), high permeability (317–320.7 mD), and low water saturation (32–44%). Moderate Vsh wells (GS323-2A) show reduced porosity (13%), permeability (220 mD), and increased water saturation (46%), reflecting good but diminished quality. High Vsh well (GS323-3) display lower porosity (12%), permeability (140 mD), and moderate water saturation (37%), indicating challenges in fluid flow. This study highlights the need for tailored strategies to mitigate high shale content and swelling clays, offering valuable insights into optimizing hydrocarbon exploration and production in shale-influenced reservoirs worldwide.