Water injection is one of the main means of improving oil recovery in oilfields where high injection pressure or low injection rate is the main problem meted. In order to exploit low permeability reservoir more efficiently, the reservoir reconstruction methods which reduce drag by amplifying pore size, such as acidification, hydraulic fracturing, are used widely. The existent problem is the possibility that the reservoir may be contaminated. Then the surface modification methods, which decrease surface tension of micro-channels, have been used in oilfield. In this paper, an innovative drag reduction method is put forwarded to decrease the drag of laminar flows of water through rock's micro-channels and then decrease the injection pressure of flooding significantly. The solution containing hydrophobic nanoparticles(HNPs) of SiO2 is injected into the micro-channels of reservoir and the HNPs are adsorbed to the wall to form a strong or super hydrophobic layer, which can lead to a slip boundary condition and decrease drag on the fluid. This mechanism has been modified with a series of experiments and simulation methods by the authors. The Scanning Electron Microscope (SEM) pictures show that a hydrophilic wall can adsorb hydrophobic nano-particles tightly and the contact angle pictures of the new surface validate that the hydrophilic wall has been turned to a strong or super hydrophobic surfaces. The core displacement experiments show that the flow resistance through nano-particles adsorbing rock's micro-channels can be reduced greatly, and about 47% of the water-phase effective permeability (WPEP) of the rock samples on average for all four core samples have been gotten, and this means that a slip effect has been made by nano-particles absorbing method. The simulation with lattice Boltzmann Method (LBM) shows that a large slip length of 0.102μm is obtained. Three oilfield tests show that the maximum injection pressure of 12.5 MPa has been dropped and this method will have good application in the development of low permeability oilfields.

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