Based on the analysis results with rheometer, spining drop interfacial tensionmeter, laser particle analyzer, microscopic oil displacement and oil displacement, a novel Preformed Particle Gel (PPG) for chemical EOR was screened out. Its application properties were evaluated. A new chemical flooding system, Heterogeneous Combination Flooding System (HCFS), was designed according to the interaction laws of PPG, polymer and surfactant. Core flooding tests were conducted under two types of reservoir conditions of Shengli Oilfeild, 1) high temperature and high salinity (HT/HS) conditions, and 2) after polymer flooding reservoir condition, to figure out the enhanced oil recovery effects of HCFS. It showed that PPG can not only migrate and penetrate in porous medium, but also generate more significant volumetric sweep efficiency by the cycle of piling up-plug-pressure rising-extending and deforming to pass through porous throats than the conventional polymer flooding to modify the existing dominant migration path. Because of the enhanced sweep efficiency introduced by the mixed PPG-polymer system with higher viscosity and viscoelasticity as well as the displacement efficiency by surfactant system, HCFS can improve the oil recovery by 22.5% for HT/HS reservoirs and by 19.1% for after the polymer flooding reservoirs in dual sandpacked tube flooding experiments with the interlayer heterogeneity of 1000:5000 × 10−3μm2.

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