Volume 65

From Contaminant to Fuel: Sustainable Upcycling of Residual Polymers via In-Situ Combustion for Enhanced Oil Recovery Jiaying Wang, Renbao Zhao, Yunpeng Zhang, Guangsen Zhu, Yuan Yuan

Abstract

As a pivotal enhanced oil recovery (EOR) technique, polymer flooding often leaves substantial residual polymers in reservoirs, causing pore-throat blockage, groundwater contamination, and ecological risks. This work pioneers the application of in-situ combustion (ISC) to post-polymer-flooded reservoirs. Self-designed combustion experiments demonstrate ISC’s dual functionality: enhancing oil recovery and degrading residual HPAM through a synergistic thermal degradation-fluid scouring mechanism. Experimental results reveal that HPAM undergoes oxidative cracking at 300–600°C to generate CO and CO₂, with degradation efficiency rising from 19.3% to 91.5%. Kaolinite catalyzes this process, reducing the complete decomposition temperature from 600°C to 450°C. For reservoirs with 100–400 µg/g residual HPAM, ISC achieves 66.8–68.9% oil recovery and 54.9-64.8% HPAM removal efficiency. Axial thermal gradients critically govern HPAM clearance: proximal to injection wells (>300°C), thermal degradation dominates; distal to production wells (<200°C), fluid scouring prevails (29.5-34.5% removal). Results show that residual HPAM could be converted into in-situ fuels (coke/gases) that sustain combustion fronts and improve oil mobility, establishing ISC as a sustainable EOR strategy for polymer-flooded reservoirs via contaminant-to-fuel conversion.

Keywords In-situ combustion (ISC), Post-polymer flooding reservoir, HPAM degradation, Thermal-fluid synergistic mechanism, Enhanced oil recovery (EOR), Contaminant upcycle