In order to explore effective approaches to enhance oil recovery in the late stage of water-flooded develop-ment in reservoirs with medium-low permeability and high-ultra-high water content,this study,taking Nanhu Oil-field as an example,deepens the understanding of reservoir microscopic characteristics through mineral analysis and SEM methods,and investigates the feasibility and application effects of dispersed particle gel in improving oil recov-ery using the combination of nuclear magnetic resonance and mercury injection methods.The results show that Nan-hu Oilfield is featured with well-developed large pore channels,obvious speed sensitivity and water sensitivity.Se-vere water breakthrough is the main reason for inefficient development,while key factors for improving development effectiveness include low-rate water injection,maintaining reservoir energy,and controlling water channeling.The dispersed particle gel can effectively inhibit water breakthrough and improve the mobilization ability of residual oil in medium and small pores.The oil recovery ratio in small pores of the core samples,in medium pores increased by 52.83 percentage points by 34.60 percentage points,respectively,after dispersed particle gel flooding,and the oil recovery increased,and the overall recovery ratio increased by 33.14 percentage points,indicating a significant im-provement in development effectiveness.The findings of this study can provide references for improving the develop-ment effectiveness of reservoirs with high water content.
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