LAUSR

Abstract CO2-EOR (enhanced oil recovery) has been widely applied in the fields to improve oil recovery while sequestrating CO2 in reservoirs to reduce the greenhouse effect. Polyacrylamide-based super-absorbent polymer (PSAP) as a plugging agent has been used in CO2/water flooding fields to manage excess CO2/water production. However, the performance of PSAP under supercritical CO2 conditions has not been systematically studied. A series of PSAP samples prepared in various salinity brines were evaluated under different pressures using newly designed high-pressure vessels to demonstrate the effect of CO2 on PSAP. The swollen PSAP samples were kept in the high-pressure vessels and pressurized using CO2 to various pressures. The vessels were kept vertically in a 65 °C oven for 1, 3, or 5 days. The PSAP samples before and after exposure to CO2 were examined, and the free water left in the vessels was analyzed. It was observed that the swollen PSAP particle size became smaller due to significant dehydration. The dehydration became more severe with time. The scanning electron microscope (SEM) images showed that the PSAP network structure was more compacted with increased testing time. The PSAP’s dehydration also increased with the increase of pressure and decreased with the increase of salinity. The re-swelling ratio was at least 91% of the original swelling ratio, and the swollen PSAP’s strength decreased by 20% after exposure to CO2, which was caused by the loss of solid content, such as loosely bonded polymers. The major reason that caused the PSAP dehydration was the CO2-induced pH effect.