The Development of Robust Particle Gel for CO2 Flooding

As a significant Carbon Capture and Storage (CCS) technology, Carbon dioxide-Enhanced oil recovery (CO2-EOR) contributed to reducing 10-20 billion tons of Greenhouse Gas (GHG) emission in U.S. The rapid increase of CO2-EOR projects indicated its enormous industrial value wherein 127 projects have been established across the country. However, the sweep efficiency of CO2 is still limited owing to its unfavorable mobility and heterogeneity of oil reservoir. Gel treatment is a low-cost, high-efficiency, and widely applicable technology to remedy such conformance problems. In spite of the versatility, conventional gel system based on copolymers of polyacrylate (PAA) and polyacrylamide (PAM) turned out to be a deficient plugging agent for CO2 flooding due to its syneresis in acidic conditions.
To improve gel performance in CO2 condition, an efficient CO2-responsive material, dimethylaminoethyl methacrylate (DMAEMA), was introduced to the gel system. In our work, particle gels containing CO2-responsive moieties, amidine group (-NCH3CH3), were successfully synthesized and optimized. Herein, a pressure-tolerate acrylic cylinder was used to assess gel swelling capacity in which CO2 presented. Moreover, the swelling performance was examined in different buffers pH varied from 2 to 7. Finally, a comprehensive characterization regarding gel rheology was carried out. Consequently, CO2-responsive gel showed 2 time of swelling ratio compared to the conventional gel at pH of 3, the acidity upon supercritical CO2 contact with water. Besides, a superior rheological property of CO2-responsive gel was observed in the rheology study. Thus CO2-reponsive gel has been considered a potential plugging agent for CO2 flooding.