Abstract
As a good deep profile control and displacement agent, polymer microspheres have broad application prospects in oil fields. Three kinds of microspheres (MG-1 to MG-3) with different particle sizes are synthesized and evaluated. The microspheres observed by SEM are regular spheres with initial particle sizes of 3μm, 6μm, and 10μm, respectively, and the swelling ratios are between 2 and 4. The matching relationship between microspheres and pore throat is established and the optimum matching factor is determined based on the long core migration experiment. The optimal matching factors of the microspheres obtained by the plugging strength are respectively 1-1.2 to MG-1 and 0.5-0.8 to MG-2. In the range of the best matching factors, the effect of injection parameters on microsphere plugging effect and profile improvement capacity is obtained by a long core migration experiment. The results show that the concentration of microspheres mainly affects the timing of their injected into the cores. The increase in concentration and injection speed will decrease the injection performance of microspheres. The concentration and injection velocity of microspheres do not affect the deep migration of microspheres in the core. Microspheres have better profile improvement and EOR effect, and the permeability ratio has less influence on them. Finally, the mechanism of microspheres with different particle sizes on profile control and displacement is studied by the microfluidic model. The results revealed that the plugging mechanism of microspheres are single microsphere direct plugging and bridging plugging with different particle size.
