Petrographic Analysis and Depositional Environment Interpretation of Sediments from Masarati Field, Greater Ughelli, Niger Delta

This study investigates the sedimentological characteristics of ditch-cutting samples from Masarati Field, Greater Ughelli, Niger Delta, Nigeria, through petrographic analysis. The objective is to determine depositional environments and reservoir quality implications based on grain size distribution and statistical parameters under PPL and XPL. The findings indicate that Wells-1 and Wells-2 could be situated in an area characterized by high precipitation rates during the Mesozoic era, a condition usually described as "excessive humidity." This paleoclimate interpretation is supported by sedimentological characteristics: particle sizes range from fine to very coarse with poor sorting, which negatively impacts reservoir quality by reducing porosity as finer grains fill spaces between coarser ones, creating tortuous pathways that decrease permeability. Well-1's bimodal distribution suggests irregular pore space distribution and variable pore throat sizes, potentially creating reservoir compartmentalization. The predominance of quartz enhances reservoir quality through its chemical stability and resistance to dissolution, while the presence of feldspars raises concerns due to their susceptibility to weathering and potential clay mineral formation that could reduce porosity. Microfractures enhance secondary porosity and fluid flow pathways, though "thin, low-quality areas" indicate potential flow barriers. Evidence of mechanical and chemical changes, including clay mineral formation and oxidation, suggests ongoing diagenetic processes that typically reduce both porosity and permeability over time. These findings improve our understanding of regional variations in reservoir quality and underscore the significance of petrographic investigations in tracing the evolution of deposits. The relationship between paleoclimate conditions, sedimentary characteristics, and reservoir properties provides valuable insights into the depositional history of the Masarati Field, Greater Ughelli region and its implications for reservoir development and production potential