Screening and Evaluation on Compound Profile Control System for Reutilization of Residual Polymer in Formation

Abstract

Flocculants for the reutilization of residual polymer in formation can be divided into two categories; the inorganic flocculants and the organic flocculants, each has its own advantages and disadvantages, and compounding inorganic and organic flocculants is promising method to make up shortcomings comes from onefold flocculant. The compound system was preliminarily screened based on the compatibility of organic and inorganic flocculants in the same system and then the optimum formula was selected based on the comparison of properties of compound systems with varying volume ratio and concentration ratio between inorganic and organic flocculants; these properties include injectivity, plugging performance, erosion resistance property and enhanced oil recovery. The screening tests were conducted under the condition simulating the existence and distribution of residual polymer in formation. The optimum formula of compound system for the reutilization of residual polymer in offshore reservoir is consist of 0.5 wt% stabilized Na-bentonite (YG340-1) and 1.0 wt% modified cationic starch; the former is inorganic flocculant with the latter the organic one. The optimized volume ratio between inorganic and organic flocculants in the selected compound system is 5:2. In compound system, the inorganic flocculant and organic flocculant enjoy complementary advantages to motivate better performance than single flocculant system in injectivity, plugging performance, erosion resistance property, with an exciting enhanced oil recovery in laboratory study.