Experimental Research on Decompression and Augmented Injection Effect by Using Active SiO2 Nano-Powder in Middle and Low Permeability cores

SiO₂ nano-powder is a new type of augmented injection agent, has the ability of stronger hydrophobicity and lipophilicity, and can be adsorbed on the rock surface so that it changes the rock wettability. It can expand the pore radius effectively, reduce the flow resistance of injected water in the pores, enhance water permeability, reduce injection pressure and augment injection volume. Using artificial cores which simulated geologic conditions of a certain factory of Daqing oilfield, decompression and augmented injection experiments of SiO₂ nano-powder were performed after water flooding. Results showed that SiO₂ nano-powder inverted the rock wettability from hydrophilicity to hydrophobicity. With the core permeability decreasing, the range of EOR of SiO₂ nano-powder flooding decreased gradually, but decompression rate increased gradually. 0.6 PV was chosen as the best injection pore volume, 0.5% was chosen as the best injection concentration. In the three kinds of permeability cores, the Oil recovery is respectively 10.97%, 8.14%, 6.84%; decompression rate is respectively 39.07%, 44.78%, 52.78%. The experimental results provide the basis for the field experiments of SiO₂ nano-powder in the middle and low permeability reservoirs.