Study On Micro Flow Characteristics Of Ordinary Heavy Oil In Viscoelastic Polymer Flooding

China has a large proven and abundant recoverable reserves of heavy oil,and thermal recovery of heavy oil is widely used.However,thermal recovery of heavy oil is limited by environmental and economic factors,resulting in poor applicability.Chemical flooding technology has been applied to heavy oil production due to its good applicability and economic efficiency.At present,the mechanism of polymer flooding for conventional crude oil has been widely applied,but the mechanism for displacing conventional heavy oil has not yet been clarified.This article first based on the basic physical properties testing experiment of viscoelastic polymer solutions,measured the viscosity concentration relationship,shear rheology,and viscoelasticity of different polymer solutions,and found that hydrophobic associating polymer solutions have strong elasticity.When the concentration exceeds 1500mg/L,shear viscosity increase phenomenon will occur,and the relaxation time is longer;Secondly,the oil recovery efficiency of polymers with different viscoelasticity and concentrations was studied through photolithography glass experiments.It was found that polymer elasticity can improve oil recovery,and the viscoelasticity of polymers is directly proportional to the concentration.Hydrophobically associating polymer solutions have a 22%increase in oil recovery compared to water flooding.Combining the photolithography glass model,a mathematical model for polymer micro displacement is constructed to study the micro flow characteristics of heavy oil in single blind end,double blind end,and porous media.In the single blind end model,the smaller the pore throat width,the stronger the role of elastic potential energy in the oil displacement process;In the double blind end model,as the elasticity increases,the degree of crude oil utilization will show a trend of first increasing and then decreasing,indicating that the elastic potential energy needs to work together with viscosity;Studying the degree of crude oil utilization during displacement of different viscoelastic solutions in a porous media model,the viscosity and elasticity of polymers can play a role in improving oil recovery during displacement.Moreover,after flowing from large pores to small pores,the frequency of "fingering" phenomenon will increase due to the aggregation of velocity and pressure.Finally,through core displacement physical experiments,the contribution rate of viscosity and elasticity in the process of viscoelastic polymer flooding ordinary heavy oil is quantitatively characterized,and the oil recovery of hydrophobic associated polymer solution is 10.1% higher than that of Xanthan gum solution;Hydrophobically associating polymer solution has the most significant effect on improving oil recovery in the concentration range of1500 mg/L-2000 mg/L.Hydrophobically associating polymer solution can exert strong crude oil production ability in the process of displacing ordinary heavy oil after association.In the hydrophobic association polymer flooding experiment,the resistance coefficient of oil displacement shows a trend of first slow,then fast,and then slow with the increase of concentration.Combined with the numerical simulation study of double blind end oil displacement,it is shown that elasticity plays a role in coordination with viscosity,but when the critical concentration is exceeded,elasticity will inhibit the viscoelastic polymer solution and continue to improve crude oil recovery.