Well Testing Analysis And Application Of Polymer Flooding Considering Dynamic Rheology

The viscoelastic model can characterize the "shear thinning" and "shear thickening" properties of polymer solutions flowing in porous media,while the power-law model and the Meter-Bird model can only describe the "shearing" of polymer solutions.At present,there are relatively few studies on the theory of well testing analysis of polymer flooding based on viscoelastic model.In this paper,the rheological curve and the time-space viscosity distribution curve of the viscoelastic model are plotted.When the shear rate is small,the polymer solution exhibits the characteristics of "shear thinning".However,when the shear rate is increased to a certain value,the polymer solution apparent viscosity gradually increases.When the shear rate is sufficiently large,the viscosity of the polymer solution peaks with a downward trend.The fall-off test is a nonlinear problem,the superposition principle cannot be used to solve it.In this paper,the changes of fluid rheology before and after shut-in of the well are discussed.It is found that the calculation using the superposition principle will lead to a smaller wellbore storage coefficient.The reasons for the difference between the two methods are analyzed.Based on this,an improved method of superposition is proposed.Considering the viscoelasticity of the polymer solution,three-region composite well testing models of polymer flooding were established.The bottom hole pressure was numerically calculated and typical well testing curves were plotted.The sensitivity analysis shows that compared with the Meter-Bird model,although the shapes of the well testing curves are similar,the hump segment and the radial flow segment of the well testing curve corresponding to the viscoelastic model significantly turns upward,so there is a big difference in the interpretation result.The use of the Meter-Bird model to characterize the rheological properties of the polymer solution will result in a small permeability of the polymer solution region.If the fluid in region 1 is polymer solution,the estimated skin factor will become too large.