Diagenesis of the Callovian-Kimmeridgian Antalo Limestone Formation, Blue Nile Basin, Ethiopia: Implications for characterizing hydrocarbon reservoir quality

Abstract

Understanding the diagenetic evolution of carbonate formations is essential for evaluating their reservoir potential. This study provides the first integrated analysis of the diagenetic process affecting the reservoir quality of the Callovian-Kimmeridgian Antalo Limestone Formation in the Blue Nile Basin. Extensive field investigations, including detailed section logging and rock sample collection, were conducted across the Dejen-Gohatsion traverse, Jemma, and Mugher areas. From the collected rock samples, 115 representative samples were selected for petrographic analysis to assess the key diagenetic processes controlling porosity and reservoir quality of the carbonate deposits. The analysis reveals that calcite cementation and dissolution are the most prominent porosity-reducing and enhancing diagenetic processes, respectively. Other processes such as compaction, dolomitization, silicification, bioturbation, micritization, and fracturing diagenetic processes have significantly influenced primary and secondary porosity development, and reservoir quality of the Antalo Limestone Formation. This study provides insight into the Antalo Limestone reservoir quality in the Blue Nile Basin. Moreover, it offers important baseline data to guide future exploration and advanced investigations aimed at re-evaluating the formation as a significant reservoir. It also enhances the current understanding of reservoir heterogeneity in Ethiopian Jurassic carbonates and contributes valuable insights for regional hydrocarbon exploration.