The Research Of Mechanical Viscosity Loss Of Polymer Injection Allocation Flooding In The Near-well Zone

Because of the high efficiency for enhanced oil recovery, the flooding polymer has dominated in the oil production. The main feature of the flooding polymer is that it can efficiently displace all varieties of residual oil due to its viscoelasticity. However, the characteristic of Pseudo plastic of the polymer solution results in a loss of viscosity when polymer flows the zone of near-well. This is because of the walls of perforation and particles of porous media leading to the deformation and degradation due to mechanical shearing, absorbing, stretching, which has a side effect on the enhanced oil recovery and makes the viscosity decrease. Therefore, it has become the most promising research orientation of analyzing the cause of viscosity loss and studying the process of the mechanical degradation in the petroleum engineering field. Nowadays most researchers pay their attention to the mechanism of coupled polymer flow and the effect of viscosity on enhanced oil recovery. While insufficient efforts have been contributed to studying the influence of characteristic parameters of near-well zone on the viscosity loss. Therefore, the influence of the mechanical shearing of the near-well zone on the viscosity of polymer solution will be investigated with theoretical analysis, finite element method and experiment. The principal content of the research includes:Flow conditions of the polymer solution in the near-well zone was analyzed, the major structure characteristics of the near-well zone was investigated. The two-dimensional model which can reflect the features of the perforation and porous media. The formulation of the viscosity and shear rate of polymer solution as functions of the principal characteristics of the porous media and perforation was established, which could be used to select the suitable modules for simulation and build the formulations of the polymer solutions.The realistic flow conditions of the polymer solutions was investigated using theoretical analysis and finite element method in the perfectly conditions of leaving out the absorbing. The formulation that can reflect the viscoelasticity and stress state of the polymer solution was obtained besides the simulation modules of the perforation and near-well zone was developed. The effect of the radius of the perforation and the permeability of the near-well zone as well as the concentration and flux of the polymer solutions on the viscosity loss was identified which was based on the previous simulation models.A polymer solution rheological property test rig, which could be applied to detect the relation of the viscosity of the solution and the shear rate, was built and the rheological curves of the polymer solution was obtained. An effect of concentration of polymer solution on the key parameters of the constitutive equation of Carreau and power-law non-Newtonian was analyzed. An experimental system, which can detect the relation of the viscosity and the permeability as well as the concentration of polymer solution constructed. The related experiments which made use of the previous system was demonstrated. The experimental results were consistent with simulation results.