Marine carbonate shoal reservoirs: review and perspectives

Understanding marine carbonate shoal reservoirs is crucial because of their substantial contribution to global hydrocarbon reserves and the formidable challenges arising from their strong heterogeneity and low permeability. Nevertheless, a comprehensive synthesis of their sedimentological characteristics, stratigraphic responses, and genetic mechanisms remains lacking. To address this gap, we present a systematic review of four globally representative ancient shoal reservoirs: the Persian Gulf, Western Canada, Gulf of Mexico, and Sichuan Basin. These basins were selected for their diverse geological settings, ages, and reservoir types, collectively capturing the global variability and fundamental features of shoal reservoirs. Our analysis demonstrates that (1) paleoenvironment conditions and relative sea-level fluctuations are the primary factors controlling shoal development, (2) syndepositional dissolution and dolomitization are key diagenetic processes enhancing porosity, and (3) multi-stage geological evolution produces complex pore systems and pronounced heterogeneity. The integrated analysis of genesis, distribution, and properties using theoretical frameworks and practical case studies confirmed the robustness and broad applicability of these findings. This review offers fundamental insights into paleoenvironment reconstruction, reservoir prediction, deep and ultra-deep exploration, and CO2 geological storage. Thus, it provides valuable guidance for the efficient development of shoal-type hydrocarbon resources and the advancement of sustainable energy strategies.