Mechanism Of Viscosity Loss Improvement In Polymer Injection System

The viscosity of polymer solution is a key index affecting the effect of polymer flooding.However,at present,the research results on how to effectively reduce the polymer viscosity loss,improve the viscosity retention,and the systematic evaluation of the viscosity loss of the injection system only stay in the phenomenological description of the field appearance,and lack of the indoor research and the mechanism analysis of the viscosity loss.Therefore,the Research on the improvement mechanism of the viscosity loss of the polymer injection system is of great significance to the EOR of polymer flooding.This paper analyzes and evaluates the reasons of viscosity loss one by one from polymer mother liquor configuration to single well target fluid compound transportation by using"node advancing analysis method".Through chemical degradation laboratory test,it is found that Fe²⁺and S^2-have the greatest influence on the viscosity loss of polymer solution.The viscosity loss rate of polymer solution reaches 55%when Fe²⁺concentration is 1 mg/L,and44%when S^2-concentration is 1.5 mg/L;the effect of cone flow regulating valve core and tank sampler on polymer solution viscosity loss is also discussed In addition,sulfate reducing bacteria and saprophytic bacteria have a long-term i MPact on the viscosity loss of polymer solution,with an average viscosity loss rate of 10.6%,which increases with time.According to the existing research basis,the indoor experiment was carried out by aeration device.The removal rate of Fe²⁺and S^2-in water by aeration process was 100%.The bactericidal and bacteriostatic laboratory and field tests were carried out for the microorganisms that affect the viscosity loss,and the combined bactericide（No.SYS-01）mainly composed of quaternary ammonium salt was optimized.When the concentration between 50 ppm of 30 ppm,the bactericidal rate from the water storage tank to the wellhead was above 99.5%,which had good bactericidal effect and reduced the viscosity loss.Aiming at the influence of mother liquor flow regulator,inter well pressure difference,water quality on viscosity loss and the influence of sampler error on viscosity loss detection,this paper carries out in-depth analysis and Research on the influence of mother liquor flow regulator,inter well pressure difference and water quality on viscosity loss detection.Two dimensional modeling is carried out by Workbench,three-dimensional modeling is conducted by Solidworks,and fluid dynamic analysis is conducted by using Fluent software Development of valve core and tube sampler.Compared with the traditional cone valve core,the viscosity loss rate of corrugated slug flow regulating valve core is reduced by 36.2%;Compared with the traditional tank sampler,the viscosity loss rate of the self-developed coil type sampler is controlled at 1.9%,with a reduction rate of 58%,and the effect is remarkable.Through the practical application in the field,the new aeration process for the initial preparation mother liquor,the target liquid flowing through the self-developed corrugated slug flow regulating valve core and tubular sampler,and the microbial degradation of the combined bactericide all reduced the viscosity loss by 38%,but the viscosity loss was still more than 5%affected by the injection environment.Once again,by examining the adaptability of the pressure grouping operation method,it is found that the viscosity loss rate will be controlled at 4.6%and the polymer viscosity retention rate will reach 93%by using the pressure grouping operation mode of one pump multi well and one pump single well.