Polymer Microspheres In Low Permeable Fracture Reservoir Oil Displacement Effect Research

This thesis carried out the research of profile control and flooding performance of polymer microspheres in low permeability reservoirs. Based on the experiments we screened a specific polymer microsphere which can smoothly flow through fractures to plug low permeability layers. Thus polymer microspheres will realize the deep profile control function in low permeable reservoirs. During the experiments low permeability core models were used to simulate alternating injection process of polymer microspheres and surfactant with ultralow interfacial tension. The profile control function of polymer microspheres can improve sweep efficiency meanwhile the high interface activity of surfactant will increase oil displacement efficiency. The synergistic effect will enhance oil recovery of low permeability reservoirs.Firstly, the swell time and particle size difference of before and after expansion were measured. The percolation capacity of polymer microspheres before and after expansion was studied in different permeability cores. To analyze the profile control function and adaptability of polymer microspheres in low permeability reservoirs.Secondly, the injection ability of different systems in the same permeability cores was researched. Experimental results show that in the cores with permeability of 10×10^-3μm² and 25×10^-3μm² cross-linked weak polymer gel and viscous polymer-surfactant effect fast however the plugging rate of polymer microspheres is slow. In these two cores the plugging ratio of three systems all can reach 98%. While in the cores with permeability of 100×10^-3μm² and 1000×10^-3μm² the plugging ratio of cross-linked weak polymer gel and viscous polymer-surfactant is 98% and polymer microspheres is only 95%.Finally, two parallel tube core model displacement experiments were conducted to research alternating injection times of profile control agents and surfactant. In the core with permeability of 100×10^-3μm² the oil recovery of alternate four times is higher than that of alternate three times and when the plugging ratio surpassed 90% the ultralow interfacial tension played a major role. However, in low permeability cores with permeability of 10×10^-3μm² and 25×10^-3μm² profile control function is a significant factor. The profile control slug size and oil recovery of alternate three times is both greater than that of alternate four times.