Experiment on multiphase flow rules in stress-sensitive fractured reservoirs

In view of the problem that the injection pressure does not increase or the increase is not obvious during the fracturing or injection process of the reservoirs with hidden fractures, the study on multiphase flow rules was performed by using physical simulation experiments. The large-scale 3D cores from stress-sensitive fractured reservoirs and the large-scale 3D cores from pure sandstone reservoirs were made to test and analyze stress sensitivity of different cores. The near-piston-like displacement and non-piston-like displacement experiments were carried out to analyze multiphase flow rules. By using the reservoir numerical simulation inversion method, the stress-sensitivity mechanism of stress-sensitive fractured reservoirs and the formation mechanism of water flooding and water channeling were clarified. The research results show that the stress-sensitive fractured reservoirs have strong stress sensitivity, and the flow capacity of the reservoir increases due to the influence of fractures or fracture opening during the displacement process; there are two water flooding fronts in the macroscopic and microscopic perspectives, that is, the water flooding front in the fractures and the water flooding front in the matrix; channeling along surface is one of the most important channeling patterns in stress-sensitive fractured reservoirs, which can easily lead to extremely uneven water flooding. The study reveals the flow rules and water channeling mechanism of multiphase fluids in stress-sensitive fractured reservoirs, which can provide a scientific guidance and theoretical basis for efficient development and optimal design of stress-sensitive fractured reservoirs.