Optimization of Chemical Flooding Injection System and Enhanced Oil Recovery after Water Flooding in Block J16, Liaohe Oilfield

To address the pronounced heterogeneity and preferential water channeling through high-permeability zones in the medium- to high-permeability reservoirs of Block J16, Liaohe Oilfieldfactors that constrain recovery and limit the effectiveness of water floodingthis study systematically investigates chemical-flooding strategies for enhanced oil recovery. We conducted a comprehensive characterization of the supplied polymer (L-PAM), surfactant, and pre-cross-linked gel particles (PPG). Using a large-scale, three-dimensional heterogeneous physical model, we compared the displacement performance of a binary composite system (polymer + surfactant) and a heterogeneous composite system (polymer + surfactant + PPG). Experimental results show that L-PAM exhibits satisfactory thermal stability, salt tolerance, and long-term property retention. The binary system attains ultralow interfacial tension, whereas the heterogeneous system markedly enhances viscoelastic characteristics. Oil-displacement experiments indicate that the heterogeneous + binary composite system delivers the best recovery outcome, achieving a final recovery of 77.75%, representing an improvement of approximately 28.7% over conventional water flooding. By effectively plugging high-permeability channels, this system substantially improves sweep efficiency in medium- and low-permeability zones and reduces water cut by up to 36.49%. Monitoring of oil-saturation distribution further confirms that the heterogeneous + binary system promotes fluid diversion and profile modification through physical plugging and flow-path alteration, thereby increasing fluid intake in medium- and low-permeability layers. These findings provide experimental evidence and technical guidance for the design and optimization of chemical-flooding strategies for field application.