Well Test Analysis Of Polymer Flooding Based On Fractal Theory

Polymer flooding makes a great contribution to maintain China's crude oil production.Oilfield examples demonstrate that the high viscosity and adsorption of polymer solutions cause formation plugging.Then the bottom hole pressure rise and the injection rate decrease.Formations near some wells even produce micro-cracks.In recent years,major oil fields adopt hydraulic fracturing to solve these issues.Therefore,the research on the influence of microcracks and hydraulic fractures on polymer solution's injectivity is significant.Based on the research of the transient flow mechanism of polymer flooding,an effective viscosity model of polymer solution is established considering the effect of viscoelastic and mechanical degradation.According to the conceptual model,the viscoelasticity and mechanical degradation of polymer solution only occurs in the near wellbore area.The polymer solution on a larger scale maintains shear thinning rheology.Using the fractal theory to study the effect of micro-cracks in polymer solution flow.Then establish the well test models including two-zone composite reservoir,three-zone composite reservoir and two-zone composite dual-porosity reservoir.Using bilinear flow analysis method to establish the finite conductive vertical fractured well test model.The Stehfest numerical inversion method and finite difference method is used to solve these models.Furthermore,the typical curve is drawn and the curve shape and parameter sensitivity is analyzed.The injection well diagnostic tools for polymer solutions include injectivity index,Hall plot,Hearn plot and so on.These methods and the decline curve analysis method is essentially the same.The main purpose is to study how the injection rate and pressure changing over time,and then get some physical parameters.Therefore,according to the well test models of polymer flooding and the material balance time,establish the modern decline type curves including Agarwal—Gradner,NPI and Transient.Then the curve shape and parameter sensitivity is analyzed.