Mechanism Study Of Multi-phase Foam System For Profile Control And Flooding In Fractured Low Permeability Reservoirs

Fractured low permeability reservoir is a typical dual porosity reservoir, fractures are the main flow channel and matrix is the main storing space of the fluid. Due to the difference in permeability, in the process of oilfield development, cross flow is easy to occur in the crack, while making the matrix of crude oil is hard to be driven and leading to a decreased sweep volume.According to the production technical difficulties of fractured low permeability reservoir, the multiphase foam complex system increase the reservoir recovery efficiency were studied in this paper. By optimizing the surfactant and evaluating the polymer microspheres performance to determine the multiphase foam system with better foaming properties and the influence of temperature, pressure, salinity, etc. on the swelling properties of the polymer microspheres were also analyzed. The stability of multiphase foam system was characterized by surface tension and Zeta potential of the surfactant HY-2, and foam stability factors were studied experimentally. Glass etching microscopic model was used to simulate multiphase foam system flow state in porous media and flooding mechanism of different micro-displacement modes were analyzed. Using core cutting technology to make fractured low permeability cores and studying the seepage law of water flooding, surfactant flooding, polymer microspheres flooding and multiphase foam flooding in fractured low permeability cores. The flooding effects of multiphase foam system on the fractured low permeability cores after oil saturated was also studied by single core flooding and parallel core flooding experiments.Experimental results show that the preferred multiphase foam system which compounding 0.6% HY-2 with 0.7% multiphase has a high foaming ability. In the Etching the micro-glass model, the multiphase foam system can block flow passage effectively, so that the surface active agent can enter low permeability porosities. Fractured low permeability core flooding experiments revealed that multiphase foam flooding effect is much higher than water flooding, surfactant flooding, conventional foam flooding, polymer microspheres flooding. With gas and liquid ratio of 1:1, foam sealing ability is strongest. Permeability ratio can influence the plugging ability of multiphase foam complex system.But even the ratio is 7.2, multiphase foam system can also make the fluid diverting. The recovery efficiency of multiphase foam complex system is much higher than that of water flooding and surfactant flooding on the cutting core displacement experiment. The reservoir recovery efficiency of multiphase bubble of fractured low permeability can be increased 30%. Therefore, multiphase foam system flooding technology for fractured low permeability has relatively broad application prospects.