Synthesis and the delayed thickening mechanism of encapsulated polymer for low permeability reservoir production

• Published in: Journal of molecular liquids 2022-08, Vol.360, p.119394, Article 119394
• Main Authors: Gong, Jincheng, Wang, Yanling, Cao, Xulong, Yuan, Fuqing, Ji, Yanfeng
• Format: Article
• Language: English
• Subjects: Delayed thickening; Microencapsulation; Polymer thickener; Polyurethane; Shell-core ratio
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2022.119394

[Display omitted] •An encapsulated polymer thickener (ECP) with a shell core structure was prepared.•ECP can delay the thickening time of polymer latexes up to 9 d.•Particle size, shell morphology, degradation temperature, and reserve of ECP were dependent on shell-core ratio.•The dispersion stability and delayed thickening performance of ECP were evaluated.•The delayed thickening mechanism of ECP was clarified. Polymer flooding is a common oil recovery technology. However, the polymer solution is difficult to be injected into low permeability reservoirs due to its high viscosity, making the reservoir reserves unable to be produced. To help tackle this problem, the encapsulated polymers with different shell-core ratios were synthesized with polyurethane as the shell material, and the delayed thickening of polymer latex in the water medium was achieved. The encapsulated polymers were characterized by DLS, SEM, TEM, and TGA to determine the shell-core ratio. The results showed that the encapsulated polymers with the shell-core ratio of 0.25 had a uniform particle size distribution (297.8∼531.8 nm), smooth and regular shaped shell, and high thermal degradation temperature (221.6 °C). These features facilitated the delayed thickening and stable dispersion of encapsulated polymers in the aqueous medium. When the concentration of encapsulated polymer was 1500 mg/L, the flocculation of microcapsules in aqueous medium was negligible, and the viscosity of the fluid increased from 1 mPa∙s to 12.84 mPa∙s after 9d. In addition, this work elucidated the delayed thickening mechanism of encapsulated polymer, and it contributed to future applications of this material in low permeability reservoirs.