Study on Variation of Reservoir Parameters Under Different Water Flooding Intensity

Water injection is generally an important measure for enhancing oilfield development performance. For medium-to-high porosity and permeability unconsolidated sandstone reservoirs, prolonged waterflooding leads to significant alterations in reservoir physical properties and microscopic pore structure. This study takes P Oilfield as an example, systematically analyzing the variations in rock composition, petrophysical parameters, grain size distribution, pore-throat structure, and heterogeneity during waterflooding by examining sealed core data from well pairs (with consistent reservoir architecture and an interwell spacing of approximately 30 m) at different water-cut stages (non-flooded, weakly flooded, moderately flooded, and strongly flooded). The results indicate that as waterflooding intensity increases, the mineral composition of the reservoir undergoes notable changes, the grain size distribution range gradually narrows, and the percentage of coarse sand and clay content significantly decreases. The pore-throat radius distribution curve shifts toward larger pore-throats, while porosity and permeability exhibit an initial decline followed by an increasing trend. Based on these findings, a staged and differentiated waterflooding development strategy is proposed, providing both theoretical foundations and practical guidance for the efficient development of similar reservoirs.