Physical simulation experiment on enhanced oil recovery by agent-pattern synergy in mature oilfields

There are short plateau periods of water-cut valley， low production and low efficiency in some wells， and limited enhanced oil recovery when chemical flooding is used to enhance oil recovery in mature oilfields developed by water injection. To address this issue， the high-permeability oil reservoirs of the five sand groups of the Third Member of the Dongying Formation （Ed3） were taken as the research objects in the Second Block of Shengtuo Oilfield， and physical simulation experiments on the binary composite flooding and the binary composite flooding （agent） and well pattern infilling （pattern） were carried out. Research indicates that the synergistic effect of polymer and surfactant improves the mobility ratio and reduces oil-water interfacial tension during binary composite flooding， leading to a 40.0% decrease in water cut and an estimated ultimate recovery of 51.0%. By infilling well pattern during binary composite flooding， the water cut is further reduced by 4.0%， and the estimated ultimate recovery increases by an additional 8.2%. The binary composite flooding system and well pattern infilling exhibit strong synergy （agent-pattern synergy）. The binary flooding system cultivates， develops， and expands enriched residual oil zones （oil walls）， achieving secondary enrichment of residual oil. Well pattern infilling enhances reserve control， mobilizes oil in relatively low-permeability zones and inter-well residual oil， and further expands the sweep area by 17.1%.